Franklin's bumble bee (Bombus franklini) Species Status Assessment

Franklin’s bumble bee (Bombus franklini)

Species Status Assessment

__________________________________________________

Photo of Bombus franklini by Pete Schroeder

Final Report (Version 1)

June 25, 2018

Prepared by Jeff Everett from the Oregon Fish and Wildlife office, Portland, Oregon; with

assistance from Nadine Kanim (Yreka Fish and Wildlife Office), Rebecca Migala (Pacific

Region Office), and Deb Giglio (Pacific Southwest Region Office).

Acknowledgements

We would like to thank the following individuals who provided substantive information and

insights for our analysis: Gene Pierce, United Stated Department of Agriculture, National

Agricultural Statistics Service; Jon Jinings, Oregon Department of Land Conservation and

Development; Stephen Haney and Steve Godwin, Bureau of Land Management; Sheila Colyer

and Bill Shaupp, U.S. Forest Service; Jennifer Syzmanski, Pepper Trail, and Tamara Smith, US

Fish & Wildlife Service; Dr. Robbin Thorp, University of California at Davis; Rich Hatfield,

Xerces Society; Peter Schroeder; Dr. Andony Melathopolous, Oregon State University; Dr. Carol

Ferguson, Southern Oregon University; Robin Fallshear, Califonia Department of Fish and

Wildlife; Dr. Sheila Colla, York University; Sydney Cameron, University of Illinois at Urbana-

Champaign; Sarah Kincaid and Helmuth Rogg, Oregon Department of Agriculture.

Executive Summary

This document presents the species status assessment (SSA) for Franklin’s bumble bee (Bombus

franklini), completed to characterize the species’ overall viability. To characterize viability we

use the three conservation biology principles of resiliency, representation, and redundancy. We

identify the species’ ecological requirements for survival and reproduction at the individual,

population, and species levels, and describe risk factors influencing the species’ current and

future condition.

Bombus franklini has the most restricted range of any North American bumble bee, and possibly

the most restricted range of any bumble bee in the world. Historically, B. franklini occupied

portions of Douglas, Jackson and Josephine Counties in southern Oregon, as well as Trinity and

Siskiyou Counties in northern California. Since the late 1990s, B. franklini observations have

declined significantly, and none have been observed since 2006, despite an expanded and

focused survey effort. Very little is known about B. franklini; much of the information presented

in this SSA is inferred from closely-related Bombus species, and we rely heavily on information

from species experts. While the decline of B. franklini observations is contemporaneous with the

decline of other Bombus species, the causal factors behind these declines are poorly understood.

The species has likely been affected by pathogens, pesticides, and the effects of small population

size. The synergistic effects of several stressors to the species have likely exacerbated declines.

Bombus franklini has been found in a wide array of sheltered and exposed habitat types at a

broad elevational range, and the species appears to be a generalist forager. Our certainty

regarding the species’ habitat needs is limited to (1) floral resources for nectaring throughout the

colony cycle, and (2) relatively protected areas for breeding and shelter. The habitat elements

that B. franklini appears to prefer to fulfil those needs are relatively flexible, plentiful, and

widely distributed. Despite this fact, no individuals of the species have been found in any habitat

since 2006, and therefore we conclude that the resiliency of the species has decreased since the

1990s. Further, no current populations of B. franklini, distributed across any level of ecological

conditions or spatial extent, are known to exist, and therefore we conclude that genetic and

ecological representation as well as redundancy have decreased since the 1990s. Due to the lack

of observations of the species since 2006, we did not project anticipated future states of

resiliency, redundancy or representation. Although the failure to detect a species during surveys

is not equivalent to a conclusive demonstration of its absence and may simply reflect the very

low detection probability for rare species, the certain losses in both the number of populations

and their spatial extent render B. franklini vulnerable to extinction even without further external

stressors acting upon the species.

Contents

Acknowledgements ....................................................................................................................................... 2

Executive Summary ....................................................................................................................................... 3

1.0 Introduction, Analytical Framework, and Methods ................................................................................ 6

1.1 Introduction ........................................................................................................................................ 6

1.2 Analytical Framework ......................................................................................................................... 7

1.2.1 Resiliency ..................................................................................................................................... 7

1.2.2 Representation ............................................................................................................................. 7

1.2.3 Redundancy ................................................................................................................................. 8

1.3 Methods .............................................................................................................................................. 8

2.0 Species Information .............................................................................................................................. 10

2.1 Background ....................................................................................................................................... 10

2.1.1Taxonomy and Species Description ............................................................................................ 10

2.1.2 Distribution and Known Occurrences/Survey Data ................................................................... 11

2.2 Species Ecology ................................................................................................................................. 17

2.2.1 Individual Level Ecology ............................................................................................................. 17

2.2.2 Population level ecology ............................................................................................................ 19

2.2.3 Synopsis of Species Ecological needs ......................................................................................... 22

3.0 Factors Influencing the Status of the Species ....................................................................................... 23

3.1 Stressors ............................................................................................................................................ 23

3.1.1 Pathogens .................................................................................................................................. 24

3.1.2 Pesticides ................................................................................................................................... 28

3.1.3. Habitat Loss and Degradation ................................................................................................... 32

3.1.4 Livestock Grazing ....................................................................................................................... 35

3.1.5 Climate Change .......................................................................................................................... 36

3.1.6 Small Population Dynamics ........................................................................................................ 37

3.1.7 Competition from non-native bees ............................................................................................ 38

3.2 Synergistic Effects ............................................................................................................................. 39

3.3 Beneficial Actions .............................................................................................................................. 39

4.0 Analysis of Current Condition ............................................................................................................... 40

5.0 Analysis of Future Condition ................................................................................................................. 42

6.0 Literature Cited ..................................................................................................................................... 43

7.0 Appendices ............................................................................................................................................ 63

FIGURES AND TABLES

FIGURE 1. ALL KNOWN OCCURRENCES OF B. FRANKLINI BY YEAR OF OBSERVATION (XERCES AND THORP 2010,

BROOKS 1999; CODE AND HANEY 2006, P. 3; POOL 2014, ENTIRE; COLYER 2016, ENTIRE; HATFIELD, PERS.

COMM. 2017; THORP, PERS. COMM. 2017) ....................................................................................................... 13

FIGURE 2. ALL KNOWN OCCURRENCES OF B. FRANKLINI, FROM 1923 TO THE PRESENT ........................................... 14

FIGURE 3. HISTORIC OBSERVATIONS AND SURVEY EFFORT……………………………………….……………………………………………16

TABLE 1. THE ECOLOGICAL REQUISITES FOR SURVIVAL AND REPRODUCTIVE SUCCESS OF B. FRANKLINI

INDIVIDUALS. ...................................................................................................................................................... 19

TABLE 2. THE REQUISITES FOR SURVIVAL AND REPRODUCTION SUCCESS OF B. FRANKLINI POPULATIONS. ............. 22

TABLE 3. ECOLOGICAL REQUIREMENTS FOR SPECIES-LEVEL VIABILITY IN B. FRANKLINI ............................................ 23

TABLE 4. ACRES OF AGRICULTURAL CROPLAND AND TOTAL ACRES ........................................................................... 33

TABLE 5. HUMAN POPULATION GROWTH ESTIMATES FOR DOUGLAS, JACKSON, AND JOSEPHINE COUNTIES IN

OREGON AND ASHLAND, OREGON. .................................................................................................................... 34

LIST OF ABBREVIATIONS

SSA Species Status Assessment

ESA Endangered Species Act

N Population Size

Effective Population Size

λ lambda, population growth rate

3Rs Resiliency, Representation, and Redundancy

spp. Species

USFS United States Forest Service

FWS Fish and Wildlife Service

BLM Bureau of Land Management

EPA United States Environmental Protection Agency

1.0 Introduction, Analytical Framework, and Methods

1.1 Introduction

This report presents the species status assessment (SSA) conducted for the Franklin’s bumble

bee (Bombus franklini). We, the Fish and Wildlife Service (Service), were petitioned to list B.

franklini as endangered under the Endangered Species Act of 1973, as amended (ESA), on June

23, 2010, by the Xerces Society for Invertebrate Conservation and Dr. Robbin Thorp, Professor

Emeritus from the University of California (Xerces Society and Thorp 2010, p. 2). In September

2011, the Service announced in the Federal Register that the petition presented substantial

information indicating that this species may be warranted for listing, and announced the

beginning of a status review for the species (Fish and Wildlife Service 2011). This SSA will be

the biological underpinning of the status review and the Service’s forthcoming 12-month finding

on whether B. franklini warrants protection under the ESA.

This SSA assesses the viability of Bombus franklini; that is, the likelihood that the species will

sustain populations over time. To assess B. franklini’s viability, we used the three conservation

biology principals of resiliency, representation, and redundancy (Shaffer and Stein 2000, pp.

308-311). These principals are described in general terms below, and more specifically for B.

franklini in section 4.0. Our approach for assessing B. franklini’s viability involved three stages.

In Stage 1, we describe the species ecology in terms of the 3Rs, identifying the ecological

requirements for survival and reproduction at the individual, population, and species levels. In

Stage 2 we use these ecological requirements to determine the baseline condition for the species

by assessing the species historical and current condition in relation to the 3Rs, and identifying

past and ongoing factors that led to the species current condition. Finally, in Stage 3 we use both

the baseline conditions as well as forecasts of the future levels of influence factors to project the

future condition of B. franklini.

Although there is abundant information available on the sub-genus Bombus sensu stricto, there is

very limited information available on B. franklini in particular. In 2016, the Service completed

the Rusty Patched Bumble Bee (Bombus affinis) Species Status Assessment (U.S. Fish and

Wildlife Service 2016a). Bombus franklini shares a close evolutionary relationship and shared

natural history traits with B. affinis (S. Colla, York University, Toronto, Ontario, Canada, 2018,

pers. comm.). We note that despite this taxonomic relationship there are distinct differences

between the species, particularly the more restricted range and limited distribution of B. franklini

compared to B. affinis. However, based on the close taxonomic relationship, B. affinis has been

identified as an acceptable proxy species to use in our assessment of B. franklini (R. Thorp,

University of California, Davis, California, pers. comm., 2017; Williams et al 2014, p. 114;

Goulson 2010, pp. 188-189; Thorp 2004; Schroeder pers. comm. 2017; Hatfield pers. comm.

2017). Due to the limited information on B. franklini, and in an effort to avoid duplicating effort

when assessing two very similar species, our SSA incorporates a portion of the information and

text provided in the rusty patched bumble bee SSA. Additionally, we note that the western

bumble bee (B. occidentalis) is also a member of the sub-genus Bombus sensu stricto, and shares

a portion of the range; therefore we also rely on information related to B. occidentalis for this

assessment of the status of B. franklini.

1.2 Analytical Framework

To assess the viability of Bombus franklini, we applied the conservation biology principles of

resiliency, representation, and redundancy (henceforth, 3Rs). Viability is the likelihood that the

species will sustain populations over time. To do this, a species must have a sufficient number

and distribution of healthy populations to withstand changes in its biological (e.g., novel

diseases, predators) and physical (e.g., climate change) environment, environmental stochasticity

(e.g., wet or dry, warm or cold years), and catastrophes (e.g., severe and prolonged droughts).

Viability is not a single state — viable or not viable; rather, there are degrees of viability--less to

more viable, or low to high viability. As the resiliency, representation, and redundancy of a

species increases, the species is better protected against the vagaries of the environment, and thus

it can better tolerate stressors (one or more factors that may be acting on the species or its

habitat, causing a negative effect). When the 3Rs increase, a species is more able to adapt to

future changes, and therefore, it is more viable. The 3Rs framework (assessing the health,

number, and distribution of B. franklini populations relative to frequency and magnitude of

environmental stochasticity and catastrophic events across its historical range of adaptive

diversity) is useful for describing the species’ degree of viability through time.

1.2.1 Resiliency

Resiliency is the ability of a species to sustain populations in the face of environmental variation

and transient perturbations. Environmental variation includes normal year-to-year variation in

rainfall and temperatures, as well as unseasonal weather events. Perturbations are stochastic

events such as fire, flooding, and storms. To be resilient, a species must have healthy populations

that are able to sustain themselves through good and bad years. Resiliency increases as the

number of individuals and populations increase, and the amount and distribution of available

habitat increases. For many species, resiliency is also affected by the degree of connectivity

among populations and the diversity of occupied ecological niches. Connectivity among

populations increases the genetic health of individuals (heterozygosity) within a population.

Furthermore, by increasing the potential for immigration, connectivity enhances a population’s

ability to recover from disturbances. Diversity of climate niches improves a species’ resiliency

by guarding against disturbances and perturbations affecting all populations similarly (i.e.,

decreases the chance of all populations experiencing bad years simultaneously or to the same

extent).

1.2.2 Representation

Species-level representation is the ability of a species to adapt to near and long-term changes in

the environment; it is the evolutionary capacity or flexibility of a species. Representation is the

range of variation found in a species, and this variation--called adaptive diversity--is the source

of species’ adaptive capabilities. Representation is therefore measured through the breadth of the

species’ adaptive diversity. The greater the adaptive diversity, the more responsiveness and

adaptability the species will have over time, thereby enhancing its viability. Maintaining adaptive

diversity includes conserving both the ecological and genetic diversity of a species. By

maintaining these two sources of adaptive diversity across a species’ range, the responsiveness

and adaptability of a species over time is preserved. Ecological diversity is the physiological,

ecological, and behavioral variation exhibited by a species across its range. Genetic diversity is

the number and frequency of unique alleles within and among populations.

In addition to preserving the breadth of adaptive diversity, maintaining evolutionary capacity

requires maintaining the evolutionary processes that drive evolution; namely, gene flow, genetic

drift, and natural selection. Gene flow is expressed through the physical transfer of genes or

alleles from one population to another through immigration and breeding. The presence or

absence of gene flow can directly affect the size of the gene pool available. Gene flow will

generally increase genetic variation within populations by bringing in new alleles from

elsewhere, but decrease genetic variation among populations by mixing their gene pools (Hendry

et al. 2011, p. 173). Genetic drift is the change in the frequency of alleles in a population due to

random, stochastic events. Genetic drift always occurs, but is more likely to negatively affect

populations that have a smaller effective population size (N

) and populations that are

geographically spread and isolated from one another. Natural selection is the process by which

heritable traits can become more (selected for) or less (not selected for) common in a population,

based on the reproductive success of an individual with those traits. Natural selection influences

the gene pool by determining which alleles are perpetuated in particular environments. This

selection process generates the unique alleles and allelic frequencies reflecting specific

ecological, physiological, and behavioral adaptations optimized for survival in different

environments.

1.2.3 Redundancy

Species-level redundancy is the ability of a species to withstand catastrophic events. Redundancy

protects species against the unpredictable and highly consequential events for which adaptation

is unlikely. In short, it is about spreading the risk. Redundancy is best achieved by having

multiple populations widely distributed across the species’ range. Having multiple populations

reduces the likelihood that all populations are affected simultaneously. The more widely

distributed populations are, the less likely they are to possess similar vulnerabilities to a

catastrophic event. Given sufficient redundancy, single or multiple catastrophic events are

unlikely to cause the extinction of a species. Thus, the greater redundancy a species has, the

more viable it will be. Furthermore, a greater number of populations and a greater diversity and

distribution of those populations, the more likely it is that the adaptive diversity and evolutionary

flexibility of the species will be preserved.

1.3 Methods

We gathered information to assess the viability of Bombus franklini from a variety of sources,

including the information in the 2010 Petition, our previous Federal Register notices, and our

files. In addition, we requested information from a diverse but specific audience, seeking

information on the species as well as all recent survey data from land managers and Federal

agencies. We also conducted a limited expert elicitation to collect more information and solicit

opinion on the species’ population dynamics. This elicitation included an extended interview

with Dr. Robbin Thorp, one of the petitioners and the noted species expert on B. franklini.

Additionally, we sent a questionnaire to 3 other professionals with experience and knowledge of

B. franklini (Richard Hatfield, Xerces Society; Peter Schroeder, Southern Oregon University;

and Pepper Trail, US Fish & Wildlife Service). A copy of the questionnaire can be found in

Appendix 4. We incorporated information from this elicitation effort into our analysis.

Building on the occurrence data provided in the 2010 Petition (Xerces Society and Thorp 2010,

Appendix 1) and other information gathered during our assessment, we assembled an occurrence

table and associated database of all known Bombus franklini occurrences, including information

provided by the Petitioners; information available in university and museum collections; and in

response to our requests (see Appendix 1). The table should not be considered a good

representation of actual numbers of B. franklini on the landscape because the data used to

assemble the occurrence table and database were generally collected through unsystematic,

opportunistic surveys and reporting, especially prior to 1998 (Thorp, University of California at

Davis, Davis, California, pers. comm. 2017), making it difficult to compare the number of

occurrences over time. The SSA for B. affinis generated a very rough estimate of the area of

habitat required to support a viable population of B. affinis by creating a post hoc systematic

sampling method (U.S. Fish and Wildlife Service 2016a, p. 11). This method entailed overlaying

a 10 km x 10 km grid across the range of the species and assigning a unique numerical identifier

and a textual description of the year(s) B. affinis were detected within that grid. We do not have

sufficient data on B. franklini occurrences over a similar spatial and temporal extent to conduct a

similarly comprehensive estimate. However, we do draw some conclusions about minimum

habitat requirements for B. franklini, as described in section 2.2.2.

Although we have evidence of the presence of Bombus franklini in certain areas, the lack of

systematic surveys across the historic range of the species over time prevents us from using these

occurrences to extrapolate reasonable estimates of species abundance or distribution. Many of

the occurrence records just provide point data for an occurrence, with no details on the size of the

area searched or whether or not the record reflected a comprehensive search of an area. Many

records also lack details on the level of survey effort per location (number of searchers, hours of

search effort per day, number of days per search effort). Additionally, because bumble bee nest

locations vary year-to-year, tracking individual colonies, and thus populations, over time is very

difficult. We cannot draw any conclusions on the abundance of B. franklini colonies or

population overall, since information is not available on how many individuals make up a

population (Thorp, pers. comm. 2017; P. Schroeder, pers. comm. 2017; R. Hatfield, Xerces

Society, Portland, Oregon, pers. comm. 2017). More targeted surveys were conducted in recent

years by those interested in the apparent decline of B. franklini, but they were not systematic and

only conducted in a limited number of specific sites throughout the species’ historic range. More

recent search efforts have primarily occurred on Federal land, however surveys have occurred

opportunistically on private land when access has been granted. Although it is possible that the

species may be extinct (University of California 2009), B. franklini colonies could potentially

persist in places that have not been systematically surveyed. A close relative, B. occidentalis,

was recorded in the Ashland, Oregon area in 2010, and not seen again in that area until two

individuals were observed during the focused surveys in July 2016 on Mt. Ashland (Thorp, pers.

comm. 2017).

2.0 Species Information

2.1 Background

2.1.1Taxonomy and Species Description

All of the approximately 250 species of bumble bees found worldwide (Williams et al. 2008, p.

1) belong to the genus Bombus (formerly Bremus), family Apidae, and order Hymenoptera, and

thirty species of Bombus are known in the western United States (Koch et al. 2012, entire).

Bombus franklini was first described in 1921, based on the collection of two queen specimens on

July 7, and July 8, 1917, in Nogales, Arizona (Frison 1921, pp. 147-148). The description of the

species was completed in 1922, based on one worker and one male specimen collected from an

unspecified locality in Oregon, and deposited in the United States National Museum (Frison

1923, p. 313-315; Thorp et al. 2010, pp. 5, 40). At that time, it was noted that B. franklini was

one of the rarer species of the widely distributed Bombus (Bremus) genus (Frison 1923, p. 315).

In 1970, based on museum record research and field studies, the actual location of the Nogales,

Arizona collection was called into question, and Gold Hill, Oregon, was proposed instead as the

type locality for Bombus franklini (Thorp 1970, p. 177-179; Thorp et al. 2010, p. 5, 7).

Several studies have been published on the taxonomic relationship of B. franklini to other

bumble bees (Stephen 1957, pp. 79-81; Milliron 1971, pp. 58-67; Plowright and Stephen 1980,

pp. 475–479; Thorp et al. 1983, pp. 29-30; Scholl et al. 1992, pp. 46-51; Cameron et al. 2007, p.

173). With the exception of Milliron (1971), who assigned B. franklini subspecific status under

B. terricola occidentalis, all of these studies have accorded B. franklini its own specific rank and

B. franklini is listed in the most recent world checklist of bumble bee species (Williams 1998, p.

129; Thorp et al. 2010, p. 5). Bombus franklini is also recognized as a valid species in the

Integrated Taxonomic Information System (Integrated Taxonomic Information System 2017).

For these reasons, we recognize B. franklini as a valid species and therefore, a potentially listable

entity under the ESA.

As a bumble bee of the subgenus Bombus sensu stricto, B. franklini is corbiculate (females

having pollen baskets on the hind legs) (Williams, et al. 2008, entire). In B. franklini, the hind

leg tibia outer surface (corbicula) is flat with long black fringes at the sides (Williams et al.

2014, p. 119). The species is short-tongued with a short head and the cheek (area between the

bottom of the compound eye to the insertion of the mandible) is shorter than it is wide (Koch et

al. 2012, p. 98; Williams et al. 2014, p. 119). Shorter faces and tongues are an adaptation to

extracting nectar from flowers with short corollas (Koch et al. 2012, p. 6). Bombus from this sub-

genus with short tongues also rob nectar from flowers with longer corollas, by biting holes in the

base of the corolla to access the nectar. Bombus occidentalis, a closely related species, has

mandibles with distinct teeth, possibly to aid in this behavior (Goulson 2010, p. 173). Body size

of the queens (22-24 mm, 0.86-0.95 inches) and workers (10-17 mm, 0.40-0.65 inches) is

relatively large (Williams et al. 2014, p. 119). Males are 13-16 mm (0.50-0.64 inches) in length.

In the field, B. franklini can most easily be distinguished from other similar species in its range

(e.g., B. occidentalis, B. vosnesenskii, B. caliginosus, B. vandykei, B. fervidus, B. insularis, B.

flavidus), by the inverted U-shape pattern of the yellow hairs on the anterior thorax surrounding a

central black patch and extending beyond the bases of the wings, and the lack of yellow hairs on

the abdomen (Thorp et al. 2010, p. 5-6; Williams et al. 2014, p. 119). In addition, the hairs on

the round face are predominantly black, there are yellow hairs on the top of the head, and there

are white hairs in two spots at the tip of the abdomen (Thorp et al. 2010, p. 5-6). For other

diagnostic characters that can be seen in the hand and under the microscope, please see Frison

(1921, pp. 147-148; 1922, pp. 313-315), Thorp et al. (2010, pp. 5-6), and Williams et al. (2014,

pp. 119-120).

2.1.2 Distribution and Known Occurrences/Survey Data

Bombus franklini is thought to have the most limited distribution of all known North American

bumble bee species (Plowright and Stephen 1980, p. 479; Xerces Society and Thorp, 2010, p. 6),

and one of the most limited geographic distributions of any bumble bee in the world (Frison

1923, p. 315; Williams 1998, p.129). Stephen (1957, p. 81) recorded the species from the

Umpqua and Rogue River Valleys in Oregon. Thorp et al. (1983, p. 8) also recorded it from

northern California and suggested its restriction to the Klamath Mountain region of southern

Oregon and northern California. Elevations where it has been observed range from 162 m (540

feet) in the northern part of its range, to over 2,340 m (7,800 feet) in the south of its historical

range. All confirmed specimens have been found in an area about 306 km (190 miles) to the

north and south, and 70 miles 113 km (70 miles) east to west, between 122° to 124° west

longitude and 40° 58’ to 43° 30’ north latitude in Douglas, Jackson, and Josephine counties in

southern Oregon, and Siskiyou and Trinity counties in northern California (Thorp 1999, p. 3;

Thorp 2005c, p. 1; International Union for Conservation of Nature 2009, p. 1). Twenty three of

the 43 sites where B. franklini has been located are privately owned, 18 are on Federal land (U.S.

Forest Service and Bureau of Land Management), one site is on State land, and one is on

municipal land.

Limited occurrence and observation data exist for Bombus franklini prior to 1997. Historic

observations and occurrence data includes randomly reported observations, student collections,

and museum specimens, as well as the collections and notes of interested parties, natural

resource managers, and university staff (Xerces Society and Thorp 2010, pp. 34-40). As

mentioned in the previous section, B. franklini was first observed in 1917 and first described in

1921. Between 1923 and 1992 there were 31 additional occurrences recorded in Oregon, and

seven recorded in California. Of the 38 records, 25 noted five or less bees, and only one 1968

record counted more than 12 bees at a single location (Appendix 1). For many of the occurrences

between 1923 and 1992, we do not have an understanding of whether or not the

surveyors/collectors were noting all of the B. franklini observed at that site on that day. No

survey methodologies were reported so we do not know how surveyors/collectors looked for the

bees at the various sites or how long they spent looking at a given site on a given day.

Furthermore, information about search efforts that took place where no bees were detected

(negative occurrence data) would not be on record (Thorp, pers. comm. 2017). Therefore, the

main information that B. franklini records from this period provide is documentation of presence

of the species at a given location; they do not provide a clear understanding of historic

population abundance across the range. However, Dr. Robbin Thorp has noted that in the 1960’s,

when he looked at sites where he thought B. franklini might be, he was able to find the species.

He also suspects that if others knew where to look for the species, they would have been likely to

find the species at the time (Thorp, pers. comm. 2017).

In 1997, there were two records of Bombus franklini in Oregon, each noting two bees counted.

Also that year, three queen B. franklini and nine workers were observed in the Marble Mountains

(Siskiyou County, California) study area, by a master’s student from Humboldt State University

(M. Brooks, Humboldt State University, Arcata, California, pers. comm. 1997). The study did

not survey for B. franklini specifically, but was looking at Bombus assemblages and flower

preferences based on tongue-length. Bombus franklini was observed at six specific locations

(three locations each, on two of the study’s ten total survey areas), between June 6

and August

; the bees were observed on lupine (Lupinus spp.), mountain monardella (Monardella

odoratissima), and clover (Trifolium spp.) (Brooks pers. comm. 1997; Brooks 1999, p. 11).

A survey effort specifically focused on Bombus franklini began in 1998 and continues annually,

at sites representing both a subset of historical and potential new localities for the species.

According to the information provided in the 2010 petition (Xerces Society and Thorp, 2010, p.

7), between nine and 17 historical sites (averaging 13.8 sites annually), and two to 23 additional

sites, were surveyed each year from 1998 until 2010. Some sites were visited more than once per

year, or in multiple years, and some historic locations have not been resurveyed since the

original observation of B. franklini at that location. These surveys were primarily focused on

localities in Jackson County, Oregon around the center of the historic range (Xerces Society and

Thorp, 2010, p. 9; Thorp, pers. comm. 2017). During the surveys from 1998 to 2006, B. franklini

was observed at 11 sites, including seven sites where it had not been previously documented. In

1998, 98 individuals were located at eight sites (with 81 of those individuals occurring at two of

the eight sites). In 1999, only 20 individual bees were located. Nine individuals were observed in

2000, and one individual in 2001. Although 20 were observed in 2002, only three were observed

in 2003 (all at a single locality), and a single worker bee was observed in 2006. There have been

no confirmed observations of B. franklini since the single worker in 2006. Figure 1 displays a

graph of all known presence data for B. franklini over time, from the first observation in 1923

until 2017 (2006 was the last documented occurrence). Figure 2 displays a map of all known

occurrence data for B. franklini, from 1923 to the present.

Figure 1. All known occurrences of Bombus franklini by year of observation (Xerces and Thorp 2010, Brooks 1999; Code and Haney

2006, p. 3; Pool 2014, entire; Colyer 2016, entire; Hatfield, pers. comm. 2017; Thorp, pers. comm. 2017)

YEAR

100

1923

1925

1927

1929

1931

1933

1935

1937

1939

1941

1943

1945

1947

1949

1951

1953

1955

1957

1959

1961

1963

1965

1967

1969

1971

1973

1975

1977

1979

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

2009

2011

2013

2015

2017

Bombus franklini records from 1923 to 2017

More intensive survey

effort began (1998)

Number of bees reported

Figure 2. All known occurrences of Bombus franklini, from 1923 to 2017.

In 2006, the Bureau of Land Management conducted a survey of 16 sites on the Mt. Ashland

resource area in the Medford District that were believed to provide optimal habitat for Bombus

franklini. Each site was surveyed twice by trained technicians, but no B. franklini were found

(Code and Haney 2006, p. 3).

Since 2009, a number of targeted surveys have taken place at select locations within the historic

range of Bombus franklini, in an effort to locate the species and other rare or declining

invertebrates (including Western bumble bee (occidentalis)). In 2014, the Medford District of

BLM conducted a survey for six special status meadow invertebrates, including B. franklini and

B. occidentalis. Surveys were conducted between July and September, with survey locations

based on (1) historical occurrence records for private, BLM and USFS lands, and (2) water and

floral resources. Bombus occidentalis was observed at three locations; no B. franklini were found

(Pool 2014, entire). The surveys were conducted in areas that appeared to have good quality

habitat for Bombus (S. Godwin, Bureau of Land Management, Medford, Oregon, pers. comm.,

2017).

Surveys targeting Bombus occidentalis took place on the Umpqua and Rogue River-Siskiyou

National Forests in 2015 and 2016, with trained observers covering dozens of historical locations

with a wide variety of habitat types and elevations throughout the flight season. Over a dozen

Bombus species were recorded including B. occidentalis, but no observations of B. franklini were

made (Colyer 2016, entire). Generally the surveys were conducted in habitat that would be good

for B. franklini, given that all of the sites had several different Bombus spp. detections (S.

Colyer, U.S. Forest Service, Prospect, Oregon, pers. comm. 2017).

In response to our request for information, the Xerces Society provided records of all Bombus

observations reported to Bumblebeewatch.org, between 2012 and 2017, within the historical

range of B. franklini. All reports are from incidental observations and have been confirmed by

taxonomic experts. Over 100 observations of Bombus spp. were reported from a wide variety of

land ownerships, habitats and elevations, and included 18 different Bombus species (including B.

occidentalis), however no B. franklini were observed (Hatfield, pers. comm. 2017). While this

information is not part of a standardized survey, it does represent some level of opportunistic

observation and reporting opportunity available over time within the historical range of the

species, and all are observations were verified by experts; thus we feel it is worth mentioning.

Again, no new observations of B. franklini have been made since 2006.

As mentioned earlier, Bombus occidentalis was recorded in the Ashland, Oregon area in 2010,

and not seen again in that area during the annual surveys until two individuals were observed

during the focused surveys in July 2016 on Mt. Ashland (Thorp, pers. comm. 2017). Bombus

occidentalis, like B. franklini, is not migratory and therefore must have been present in the

survey area, yet remained undetected during the surveys over multiple sequential years. This is

indicative of the low detection probability for these rare species, even when focused annual

survey efforts by trained observers are taking place.

Figure 3 below displays all the sites on record that have been surveyed for Bombus franklini.

This includes survey location information from the Bureau of Land Management, U.S. Fish and

Wildlife Service, and the U.S. Forest Service; information from the 2010 Petition (Xerces

Society and Thorp 2010, p. 34-40; additional information from Dr. Robbin Thorp (Thorp, pers.

comm. 2017) and Brooks (Brooks 1997, p. 4), as well as all Bombus observations within the

historic range of the species from 2012-2017 as reported in Bumblebeewatch.org (Hatfield pers.

comm. 2017).

Figure 3. All sites surveyed for Bombus franklini from 1923 to 2017.

2.2 Species Ecology

2.2.1 Individual Level Ecology

The specific life history characteristics or behavior of this rare species have not been studied. As

one of the rarest Bombus species, B. franklini are somewhat enigmatic and a specific habitat

study for the species has not been completed. Such a study was initiated in 2006 when B.

franklini was last seen, but could not continue due to the subsequent absence of the species

(Thorp 2017, pers. comm.). While little is known about B. franklini’s reproductive biology,

specific habitat needs or unique behavior, this information is available for Bombus in general and

for some closely-related species (B. occidentalis, B. affinis, and B. vosnesenskii, among others).

Bombus franklini is a primitively eusocial bumble bee, living in colonies made up of a queen and

her offspring – males and workers. The nesting biology of B. franklini is unknown (Xerces

Society and Thorp 2010, p. 10), but they likely nest underground in abandoned rodent burrows or

similar cavities that offer resting and sheltering places, food storage, nesting and room for the

colony to grow, as is typical for other eusocial Bombus species (Plath 1927, pp. 122-128; Hobbs

1968, p. 157; Thorp et al. 1983, p. 1; Thorp 1999, p. 5). It may also occasionally nest on the

ground (Thorp et al. 1983, p.1) or in rock piles (Plowright and Stephen 1980, p. 475), and has

even been found nesting in a residential garage in the city limits of Medford, Oregon (Thorp

2017, pers. comm,).

The flight season of Bombus franklini is from mid-May to the end of September (Thorp et al

1983, p. 30); a few individuals have been encountered in October (Southern Oregon University

Bee Collection records, in Xerces Society and Thorp, 2010, Appendix 1 page 39). Colonies of B.

franklini have an annual cycle, initiated each spring when solitary queens emerge from

hibernation and seek suitable nest sites (Thorp, pers. comm. 2017). The queen collects nectar and

pollen to support the production of her eggs, which are fertilized by sperm she has stored

throughout hibernation since mating the previous fall. In the early stages of colony development,

the founding queen (foundress) is responsible for all food collection and care of the eggs and

larvae. As the colony grows, workers assume the duties of food collection, colony defense, nest

construction, and larval care while the foundress remains within the nest and produces eggs.

Colonies of B. franklini may contain from 50 to 400 workers, and the founding queen (Plath

1927, pp. 123-124; Thorp et al 1983, p. 2; Macfarlane et al 1994, p. 7). Two colonies of B.

franklini initiated in the laboratory and set out to complete development in the field contained

over 60 workers by early September, and likely produced over 100 workers by the end of the

season (Plowright and Stephen 1980, p. 477).

Near the end of the colony cycle, reproductive queens (gynes) and fertile males are produced.

Male bumble bees patrol selected territories, which they mark with queen-attracting scent.

Queens locate a territory and remain still until a male finds her. Mating usually takes place on the

vegetation on or near the ground. Queens usually mate with only one male, but males may mate

with multiple females who enter the territory. After mating, queens feed to build up fat before

entering hibernation. At the end of the colony cycle, all the workers and the males die along with

the founding queen; only the inseminated hibernating gynes are left to carry on the line into the

following year (Duchateau and Velthius 1988). Over wintering habitat would include micro-

habitats such as ground cavities, rotting logs, loose soil and other protected sites for queens to

hibernate, with floral resources and suitable nest sites available for the emerging queens the

following spring. Mating habitat requirements for most bumble bee species is not known.

Bumble bees are generalist foragers, meaning they gather pollen and nectar from a wide variety

of flowering plants (Xerces Society 2013, pp. 27-28). Bumble bees are very efficient at

collecting pollen; unlike honey bees, they often vibrate their flight muscles while inside a flower,

causing pollen to fall from the plant anthers and stick to the bumble bee’s copious body hairs.

This behavior of “buzzing” a flower is also known as sonication, and is one of the characteristics

of bumble bees that make them particularly attractive for commercial pollination; bumble bees

can pollinate flowers hundreds of times faster than honey bees (Williams et. al. 2014, p. 16).

Bombus franklini requires a constant and diverse supply of flowers that bloom throughout the

colony’s life cycle, from spring to autumn (Xerces Society and Thorp 2010, p. 11); these

resources would typically be found in open (non-forested) meadows in proximity to seeps and

other wet meadow environments. Different Bombus species have consistently been observed

foraging in the same area visiting similar and different species of flowering plants. During some

Oregon surveys, no Bombus species was always consistent in the number of different plants

species it visited, nor was any Bombus species tied to just one plant species (Schroeder, pers.

comm. 2017). The nectar from flowers provides carbohydrates and the pollen provides protein.

Studies of other Bombus species typically exhibit foraging distances of less than 1 km (0.62

miles) from their nesting sites (Knight et al. 2005, p. 1816; Wolf and Moritz 2008, p. 422;

Dramstad 1996, pp. 163-182; Osborne et al. 1999, pp. 524-526; Rao and Strange 2012, pp. 909-

911; Hatfield, pers. comm. 2017). Bombus franklini may have a foraging distance of up to 10 km

(6.2 miles) (Thorp, pers. comm. 2017), but the subgenus’ typical dispersal distance is most likely

3 km (1.86 miles) or less (Hatfield, pers. comm. 2017; Goulson 2010, p. 94,). Bombus franklini

have been observed collecting pollen from lupine (Lupinus spp.) and California poppy

(Eschscholzia californica), and collecting nectar from horsemint or nettle-leaf giant hyssop

(Agastache urticifolia) and mountain monardella (Monardella odoratissima) (Xerces Society and

Thorp 2010, p. 11). Bombus franklini may also collect both pollen and nectar from vetch (Vicia

ssp.) as well as rob nectar from it (Xerces Society and Thorp 2010, p. 11). A short-

tongued/cheeked bumble bee, B. franklini has been found to antagonistically rob nectar from

flowering plants that it cannot directly reach with its tongue, by chewing a hole in the host plant

where the nectar is located (Pool 2014, p. 3; Schroeder, pers. comm. 2017; Hatfield, pers. comm.

2017). This particular behavior has been known to occur during its visitation to pollinator plants

such as Aconitum. Table 1 summarizes ecological requirements of B. franklini at the individual

level.

Table 1. The ecological requisites for survival and reproductive success of Bombus franklini

individuals.

Life Stage

Winter

Spring

Summer

Autumn

Queen

Diverse floral

resources;

suitable

nest habitat

Diverse floral

resources;

suitable

nest habitat

Diverse floral

resources; suitable

nest habitat

Worker Females

Diverse floral

resources in

proximity to

nest

Diverse floral

resources in

proximity to

nest

Diverse floral

resources in close

proximity to nest

Males

Diverse floral

Resources;

suitable mating

habitat

Diverse floral

resources; suitable

dispersal/mating

habitat

Gynes (new

foundress queens)

Suitable

diapause sites

Diverse floral

resources

Diverse floral

resources; suitable

dispersal/mating

habitat

In summary, Bombus franklini has been found in a wide array of sheltered and exposed habitat

types at a broad elevational range, and the species appears to be a generalist forager. Our

certainty regarding B. franklini habitat needs is limited to (1) floral resources for nectaring

throughout the colony cycle, and (2) relatively protected areas for breeding and shelter. The

habitat elements that B. franklini appears to prefer to fulfil those needs mentioned above are

relatively flexible, plentiful, and widely distributed.

2.2.2 Population level ecology

Bombus franklini has long been considered a rare or vary rare species, with a relatively small

population size and relatively small colony size compared to other Bombus species (Thorp, pers.

comm. 2017; Hatfield, pers. comm. 2017). No more than 356 individuals have been observed in

total, and no more than 98 total individuals at eight separate locations have been observed in any

one year (Xerces Soc. and Thorp 2010, p. 7; Occurrence Table, Appendix 1). We have no

definitive information on the minimum number of colonies or minimum habitat patch size for a

self-sustaining population of B. franklini. As stated above in section 1.3 the assessment for B.

affinis created a 10 kilometer (km) x 10 km (6.2 miles x 6.2 miles) grid across the range of the

species to generate a rough estimate of the area of habitat required to support a viable population

of B. affinis. The lack of information on B. franklini makes it unreasonable to do the same

comprehensive exercise for this species, however we can look at some general principles of B.

franklini life history to provide us with a very rough estimate of minimum habitat requirements

for our best guess of what constitutes a population of the species. If we focus on the minimum

area of habitat required to allow for individuals from different B. franklini colonies to travel their

typical foraging distance to forage at a common location and potentially interbreed, we find that

an area 6 km x 6 km might accomplish that. This spatial estimate is appropriate for B. franklini

for the following reasons: (1) the subgenus’ typical dispersal distance for B. franklini is 3 km

(Hatfield, pers. comm. 2017; Goulson 2010); (2) B. franklini individuals concurrently visiting a

site are often from different colonies (Hatfield, pers. comm. 2017); and, (3) colonies would have

to be within dispersal distance of other colonies in order to interbreed and maintain genetic

diversity. An area 6 km x 6 km (3.72 miles x 3.72 miles) would allow for the possibility that B.

franklini from different colonies that are 6 km (3.72 miles) apart could each disperse 3 km (1.86

miles) to a shared foraging location. It is, therefore, reasonable to assume that multiple B.

franklini detections over time within a 6 km x 6 km (3.72 miles x 3.72 miles) area would likely

represent a single population. This measure of 6 km

(3.72 square miles) is therefore a

reasonable estimate of minimum patch size for a self-sustaining population of B. franklini.

Population viability requires healthy demographics and sufficient habitat to support a healthy

demography; specifically, viability is a function of population size (N) and its population growth

rate (lambda, λ). The population structure of Bombus franklini operates similarly to a

metapopulation. A metapopulation is an assemblage of interacting subpopulations; a population

of B. franklini is a collection of interacting colonies. But, whereas a subpopulation is composed

of many reproductive individuals, a B. franklini colony is founded by a single queen, and thus a

colony represents one reproductive unit. The effective population size (N

) of B. franklini is,

therefore, the number of successful nests or colonies – not the number of individuals.

Population size also affects population viability through genetic health. Small populations have

lower levels of genetic diversity (heterozygosity), which reduces the capacity of a population to

respond to environmental change. Inbreeding depression may result, leading to reduced

longevity and fecundity and overall population fitness (Darvill et al. 2006, p. 602). Populations

of monoandrous social species like Bombus franklini (colonies headed by a single queen who

mates with a single male), are especially vulnerable to inbreeding depression, because the rate of

genetic drift in a population is determined by the effective population size (N

) which is much

lower than the number of individuals in an area (Goulson and Darvill 2008, pp. 197-198; Darvill

et al. 2006, p. 602). The N

in bumble bees is 1.5 times the number of successful nests, not 2

times, as is the case with diploid-diploid organisms (Goulson and Darvill 2008, pp. 197-198).

The reproductive system of bumble bees renders them particularly sensitive to loss of genetic

diversity. Bombus species exhibit haplodiploidy (i.e., males are haploid and females are diploid)

and exhibited a single locus complementary sex determination (sI-CSD) system (Zayed 2009, p.

238). Typically, heterozygotes at the sex-determining locus develop into diploid females from

fertilized eggs, while hemizygotes (a diploid individual with only one allele for a particular gene)

develop into haploid males from unfertilized eggs (Zayed 2009, p. 239). In cases, however,

where females mate with haploid males that share a sex-determining allele in common (called

“matched mating”), half of the females’ progeny will be homozygous at the sex-determining

locus and will consequently develop into diploid males instead of females. As males do not

contribute resources to the colony, homozygosity at the sex-determining locus imposes a cost to

the colony by decreasing the number of females produced (Ellis et al. 2006, p. 4376).

Additionally, diploid males are unviable, or if viable and mate, produce diploid sperm, which

will lead to unviable fertilized eggs or sterile triploid daughters (Zayed 2009, p. 239), so those

males that are produced are unable to contribute to next year’s cohort. Matched mating occurs

most often when allele diversity at the sex-determining locus is low (Ellis et al. 2006, p. 4376;

Zayed 2009, pp. 239-241). Thus, as N

decreases, the likelihood of producing diploid males

increase, which will further reduce the population size, potentially resulting in a negative,

reinforcing downward cycle (i.e., extinction vortex). Zayed and Packer (2005, pp. 10743-10744)

found, through modeling simulations, that extinction risks in haplodiploid populations were an

order of magnitude higher than probabilities of extinction due to inbreeding depression in diploid

populations. They attributed this high extinction risk to the effects of the “diploid male vortex”; a

phenomenon where diploid males initiate a positive feedback cycle that leads to rapid extinction.

Several species of bumble bee in England have demonstrated a dynamic consistent with this

negative, reinforcing pattern. Bombus subterraneous, for example, following reduction in

population size due to habitat loss eventually went extinct in the United Kingdom despite

continued suitability of habitat (Darvill et al. 2006, p. 608). Maintaining genetic diversity within

populations, thus, requires large N

and gene flow within and among populations.

The viability of a population is also determined by its long-term lambda; in order for any

population to persist over time, its growth rate, λ, must exceed 1.0. Species that fluctuate greatly

with environmental conditions, require strong lambdas over time to avoid extirpation. The

minimum λ needed to sustain a Bombus franklini population over time is unknown, but insects

are particularly susceptible to environmental stochasticity. Although bumble bees, because of

their relatively larger body size and fuzzy bodies, are not as strongly influenced by

environmental conditions as other insects including honey bees, climatic conditions affect the

availability of requisite resources, and hence, bumble bee numbers. Pollen and nectar

availability, especially in spring and fall when floral resources are scarcer, are influenced by

environmental conditions (Holm 1966, pp. 156-157); in years with unfavorable weather, the

supply of food is limited, leading to smaller and fewer colonies. Thus, population viability

requires occupying areas with a diversity of environmental conditions (spatial heterogeneity) to

ensure floral resources are available throughout the season and year-to-year despite variations in

climatic variables, such as temperature and precipitation. Similarly, spatial heterogeneity

increases the likelihood of asynchrony among colonies, a pre-requisite for metapopulation long-

term persistence (Hanski 1999, p. 28). In spatially heterogeneous populations, it is unlikely that

the entire population will contemporaneously experience the same environmental conditions,

thus ensuring that not all colonies comprising a population will fail due to unfavorable

conditions.

In summary, the significant determinants of population-level viability for Bombus franklini are a

healthy demography and sufficient quality habitat to support this demography. The demography

of B. franklini populations is a function of its population size (the number of successful nests)

and its population growth rate over time. The population size required to support a viable

population is likely variable across spatial scales and is unknown, but generally speaking, the

larger the population, the more genetically healthy and thus the more robust to extirpation.

Similarly, the minimum long-term λ required to sustain a population over time is unknown, but it

must exceed 1.0 and likely must be higher, given the susceptibility to environmental

stochasticity. Both of these variables, N and λ, are dependent upon the amount and quality of

floral resources, nest sites, and overwinter sites across temporal scales (within and among years).

A precise estimate of the area of habitat required to support a viable population is dependent on

the density and quality of floral resources, but given the large amount of food needed to support

successful colonies, it is reasonable to assume a large area is required. Another important aspect

of population viability is connectivity among colonies to ensure mating of unrelated reproductive

individuals and connectivity among populations to maintain within-population genetic diversity.

Lastly, the degree of spatial heterogeneity across the population area reduces the chances of all

colonies failing concurrently due to poor environmental conditions, and thus, is important for

long-term persistence. For B. franklini, we can estimate that a minimum area of 6 km

would

allow for individuals from different colonies to travel their maximum foraging distance to forage

at a common location and have the opportunity to interbreed. Based on the above, the ecological

requirements for successful population of B. franklini are listed below in Table 2.

Table 2. The requisites for survival and reproduction success of Bombus franklini populations.

Population Health (fitness)

Element

Importance

Healthy Demography

Large N

Multiple, successful colonies

Patch size at least 6 km

Successful colonies,

connectivity

Habitat connectivity

To find unrelated mates

Habitat to support healthy

demography

Sufficient floral resources

Adequate quantity of nectar

and pollen

Nesting and overwintering

sites

Safe breeding and shelter

Habitat connectivity

To safely and efficiently find

food

Heterogeneity

Diverse environmental

conditions

2.2.3 Synopsis of Species Ecological needs

Viability is the likelihood that a species will sustain populations over time. To do this, Bombus

franklini needs a sufficient number and distribution of self-sustaining populations to withstand

environmental stochasticity (resiliency), adapt to changes in its environment (representation),

and withstand catastrophes (redundancy) (Table 3).

Table 3. Ecological requirements for species-level viability in Bombus franklini

3Rs

Requisites of long-term

viability

Description

Resiliency

(able to

withstand

stochastic

events)

Interconnected, healthy

populations

across a diversity of

habitats

Populations with:

1) large N

, sufficient floral resources in close

proximity to nesting and overwintering sites,

2) connectivity among colonies, and

3) spatial heterogeneity; high connectivity

among populations dispersed across diverse

climatic conditions (spatial heterogeneity)

Representation

(to maintain

evolutionary

capacity)

Maintain adaptive

diversity of the

species

Healthy populations distributed across areas of

unique adaptive

diversity

Maintain evolutionary

processes

Maintain evolutionary drivers--gene flow,

natural selection, genetic drift- to mimic

historical patterns

Redundancy

(to withstand

catastrophic

events

Sufficient distribution of

healthy

populations

Sufficient distribution to guard against

catastrophic events wiping

out portions of the species adaptive diversity,

i.e., to reduce

covariance among populations

Sufficient number of

healthy populations

Adequate number of healthy populations to

buffer against

catastrophic losses of adaptive diversity

3.0 Factors Influencing the Status of the Species

Factors can influence a species both negatively and positively, as well as in synergy with other

factors. We focused our analysis on six primary stressors potentially negatively affecting the

species – pathogens, pesticides, habitat loss and degradation, grazing, climate change, and small

population dynamics. We then looked at potential synergistic effects between these stressors.

Finally, we looked at beneficial actions that may be positively affecting the condition of the

species.

3.1 Stressors

The 2010 Petition identified the following factors as stressors on Bombus franklini and its

habitat: introduced exotic diseases and competition from non-native bees; destruction,

degradation and conversion of habitat; pesticides and pollution; inadequacy of current rules,

regulations and law; introduction of exotic plant species; increased human use of native habitat;

climate change; and alteration of wildfire severity and frequency (Xerces Society and Thorp

2010, p. 4). In our 90-day finding on the 2010 Petition (U.S. Fish and Wildlife Service, 2011),

we noted that the petitioners provided substantial information on stressors to B. franklini from

the destruction, modification or curtailment of habitat (primarily due to the potential impacts of

natural or prescribed fire), disease, as well as the inadequacy of existing regulatory mechanisms

and other natural or manmade factors (including pesticides, small population dynamics,

competition from non-native bees, and climate change).

In this SSA, we analyzed the factors noted as leading to our substantial 90 day finding. In

addition, based on new information received, we looked again at agricultural intensification,

urban development, and livestock grazing, as well as synergistic effects of the stressors in

combination with each other. We discuss existing regulatory mechanisms and conservation

actions in section 3.3, Beneficial Actions.

3.1.1 Pathogens

A number of diseases are known to naturally occur in bumble bee populations. These include the

protozoan parasite Crithidia bombi, the tracheal mite Locustacarus buchneri, and the

microsporidium (parasitic fungus) Nosema bombi, as well as deformed wing virus. Pathogens

and parasites are widespread generalists in the host genus, but affect species differently

according to host susceptibility and tolerance to infection (Kissinger et al. 2011, p. 221; Malfi

and Roulston 2014, p. 18). The host species’ life history plays a role in the virulence of a given

pathogen; for instance, parasites may have relatively smaller effects on species with shorter

colony life cycles and smaller colony sizes (Rutrecht and Brown, 2009, entire).

Pathogen spillover is a process whereby parasites and pathogens spread from commercial bee

colonies to native bee populations (Colla et al. 2006, p. 461; Otterstatter and Thompson 2008, p.

1). The precipitous decline of certain Bombus species from the mid-1990s to present –

particularly species in the subgenus Bombus sensu stricto (including B. franklini) – was

contemporaneous with the collapse of commercially bred B. occidentalis, which were raised

primarily to pollinate greenhouse tomato and sweet pepper crops beginning in the late 1980s

(Szabo et al. 2012, pp. 232 -233). This collapse was attributed to N. bombi. Around the same

time, several North American wild bumble bee species – B. affinis, B. occidentalis, B. terricola

(all in the same subgenus Bombus sensu stricto), and B. pensulvanicus, also began to decline

rapidly (Szabo et al. 2012, p. 232).

Bumble bees are very efficient pollinators of a wide variety of crops, including fruits, nuts, and

vegetables (Loken 1958; Holm 1966b, Corbet et al. 1991, Cane and Payne 1993, MacKenzie and

Averill 1995; Goodell and Thomson 1997, Macfarlane and Patten 1997, Mayer and Lunden

1997, Stubbs and Drummond 2001, Thorp 2003). As mentioned in section 2.2.1, bumble bees

sonicate or “buzz pollinate” flowers hundreds of times faster than honey bees can. This attribute,

combined with their tolerance of temperature extremes and longer foraging seasons, make them

ideal for commercial greenhouse crop production (North American Pollinator Protection

Campaign 2006, p. 6). Roughly 95 percent of all commercially-reared bumble bee colonies are

used in the greenhouse production of tomatoes and sweet peppers (Velthuis and van Doorn 2006,

Shipp et al. 1994, Ercan and Onus 2003). Commercial bumble bee production started in North

America in the early 1990s (Xerces Society and Thorp 2010, p. 15). Queens of both Bombus

occidentalis and B. impatiens were shipped from the United States to rearing facilities in

Belgium that were also likely rearing Bombus terrestris (a closely related Bombus species native

to Europe). Bombus terrestris was also likely imported to Mexico in 1995 and 1996 for

greenhouse tomato pollination (Winter et. al. 2006, p.5).

The commercially-reared colonies produced from these queens were shipped back to the United

States between 1992 and 1994. Bumble bee producers experienced major problems with Nosema

bombi infection in commercial Bombus occidentalis in 1997 (Flanders et al. 2003, p. 108;

Velthius and van Doorn 2006, p. 432), and eventually stopped producing B. occidentalis. In

addition, the morphology of N. bombi found in a native bumble bee in China, Bombus leucorum,

was found to be the same as that found in B. terrestris imported into China from New Zealand

(Jilian et al. 2005, p. 53), suggesting the disease may have been introduced into native bumble

bee populations in China by commercial bees. Studies suggest that disease can be spread from

commercial bumble bees to nearby wild bumble bees (Niwa et al. 2004, p. 60; Whittington et al.

2004, p. 599; Jilian et al. 2005, p. 53; Colla et al. 2006, p. 461), even when commercial bumble

bees are used for pollination in greenhouses. This is because commercial bumble bees frequently

forage outside greenhouse facilities and can transmit disease at shared flowers (Xerces Society

and Thorp, 2010, p. 15; Whittington et al. 2004, p. 599; Colla et al. 2006, p. 461). In addition to

commercial pollination, B. occidentalis colonies were used in field research between 1991 and

2000 in California, Washington, and Alberta, Canada (Mayer et al. 1994, p. 21; Mayer and

Lunden 1997, p. 283; Richards and Myers 1997, p. 293; Mayer and Lunden 2001, p. 277;

Thompson 2004, p. 460).

Nosema bombi is a microsporidium (parasitic fungus) that has been detected in native bumble

bees in North America, and has been found to be a part of the natural pathogen load, reported in

Canada since the 1940s (Cordes et al. 2011, p.7) and appears to have a broad host range in North

America (Kissinger et al. 2011, p. 222). Nosema bombi infections primarily occur in the

malpighian tubules (small excretory or water regulating glands), but also in fat bodies, nerve

cells, and sometime the trachea (Macfarlane et al. 1995). Colonies can appear to be healthy but

still carry N. bombi and transmit it to other colonies. Transmission of N. bombi most likely

occurs when spores are fed to larvae (Eijnde and Vette 1993 and Rutrecht 2007, as cited in

Meeus et al. 2011, p. 666). Murray et al. (2013, p. 274 citing Rutrecht et al. 2007) notes that N.

bombi spreads slowly through novel populations with subsequent inter-colony infections through

drift of infected adults into non-natal colonies.

The effect of Nosema bombi on bumble bees varies from mild to severe (Macfarlane et al. 1995;

Rutrecht et al 2007, p. 1719; Otti and Schmid-Hempel 2008, p. 577). N. bombi can have large

effects on individual bees. Infected animals may have crippled wings, and queens may have

distended abdomens and be unable to mate (Otti and Schmid-Hempel 2007, pp. 122-123). Malfi

and Roulston (2014, p. 24) found that N. bombi infections are more frequent and more severe in

rare species and also that the species with the highest percentages of infected individuals were

rare species.

The Petitioners hypothesize that a virulent strain of Nosema bombi from Bombus terrestris

spread to B. impatiens and B. occidentalis prior to their shipment back into the United States, and

once in this country the commercially reared colonies may spread the virulent strain to wild

populations of B. franklini. In work partially funded by the U.S. Fish & Wildlife Service, surveys

for parasites and pathogens in bumble bee populations of the Pacific Northwest and Midwest

were conducted by the University of Illinois between 2005 and 2009. The goal was to assess

Bombus populations for presence and prevalence of pathogens, particularly microsporidia, in an

effort to provide baseline data to assess disease as a potential factor in the decline of B. franklini,

B. occidentalis, and B. pensylvanicus (Solter et al, 2010, p. 1). The highest prevalence of N.

bombi was found in B. occidentalis, with 26 percent of collected individuals infected. Crithidia

bombi infections of B. occidentalis were 2.8 percent overall. No B. franklini were collected

during the study. However, Mt. Ashland, Oregon (the last known location for B. franklini), was

one of only three sites in the Pacific Northwest study area where N. bombi infections were found

in multiple Bombus species (B. insularis and B. bifarius); the recovery of N. bombi infections

from multiple Bombus species at a site was otherwise rare (Solter et al 2010, pp. 3-4). Although

Cordes et al (2011, p. 7) found a new allele in N. bombi, the recent study by Cameron et al.

(2016) found no evidence of an exotic strain of N. bombi. While we have no documentation in

our files or evidence of direct effects of a virulent strain of N. bombi on B. franklini, N. bombi

has been detected in closely related species in the range of B. franklini. Furthermore, N. bombi

infections in rare species like B. franklini are more frequent, more severe and seem to affect a

higher percentage of individuals in the species.

Crithidia bombi has been shown to have detrimental effects on colony founding success of

queens, the fitness of established colonies, and the survival and foraging efficiency of bumble

bee workers (Brown et al. 200, p. 421; Brown et al 2003, p. 994; Otterstatter et al. 2005, p. 388;

Gegear et al. 2005, p. 1; Gegear et al. 2006, p. 1073). Studies suggest that C. bombi can spread

from commercial bumble bees to nearby wild bumble bees through shared use of flowers when

they escape to forage outside and transmit the disease (Durrer and Schmid-Hempel 1994, p. 299;

Whittington et al. 2004, p. 599; Colla et al. 2006, p. 461; Otterslatter and Thompson 2008, p. 1).

In fact, C. bombi has been shown to be present in higher frequencies in bumble bees near

greenhouses where commercial colonies of Bombus impatiens are used than in bumble bees

remote from these facilities (Colla et al. 2006, p. 621).

Although acute mortality is rarely observed, Crithidia bombi alters the foraging behavior in host

bees by reducing their ability to identify and manipulate nectar flowers. This causes bees with

high levels of infection to spend as much as 200 percent more time on flower visits to collect

pollen and nectar resources (Gegear et al. 2006, Gegear et al. 2005). Although C. bombi is

considered to be a bumble bee parasite, honey bees have also been shown to be possible vectors

(Ruiz-Gonzales and Brown, 2006, p. 621).

The extent to which this pathogen occurs within the range of Bombus franklini is not known.

However, within the historic range of B. franklini, B. impatiens hives were purchased and

installed by a strawberry and vegetable grower to pollinate their crops in Grants Pass, Oregon

(Associated Press 2007; Xerces Society and Thorp 2010, p. 18). Bombus impatiens is a known

vector of Crithidia bombi. Experimental evidence shows that bumble bees can contract C. bombi

while feeding on flowers that have been previously visited by infected bees (Tripodi, pers.

comm. 2016 in U.S. Fish and Wildlife 2016, p. 42), and bees from commercial rearing facilities

have tested positive for this pathogen upon delivery (Otterstatter et al. 2005, p. 388; Murray et

al. 2013, p. 274). While evidence exist that C. bombi does affect Bombus spp., we do not have

documentation in our files or evidence of direct effects of C. bombi on B. franklini.

Locustacarus buchneri is a tracheal mite that infects Bombus species in Japan, the Netherlands,

and Belguim. The specific effects of L. buchneri on Bombus species, as well as the mechanisms

for spreading the mites, are not well understood. However, Otterstlatter and Whidden (2004, p.

351) and Goka et al. (2001) cite studies that found heavy mite infestations can severely injure

bumble bees, to the extent that they are no longer able to forage (Goka et al. 2001, p. 2098).

Ottersatter and Whidden (2004) found that bumble bees containing tracheal mites have

significantly reduced lifespans in the laboratory. Commercially raised bumble bees from Europe

were found to be infested with tracheal mites at higher rates than detected in wild bees (Goka et

al. 2001, p. 2098). While evidence exists of L. buchneri effecting Bombus spp., we do not have

documentation in our files or evidence of direct effects of L. buchneri on B. franklini.

Acute Bee Paralysis was the first honey bee virus to be detected in bumble bee hosts, although its

occurrence in natural populations and effects on bumble bee health are unknown. The Black

Queen Cell Virus has been the most commonly detected bumble bee pathogen in ongoing

surveys, having been found in 31 percent of 559 samples tested to date (Tripodi, pers comm.

2016 in U.S. Fish and Wildlife Service 2016a, p. 42). It should be noted that although 12 Bombus

species across the United States have tested positive for Black Queen Cell Virus, B. franklini has

not been evaluated. The effects of this virus, which occurs not only in honey bees and bumble

bees but a number of other arthropods, are unknown (Tripodi, pers. comm. 2016 in U.S. Fish and

Wildlife Service 2016a, p. 42). We have no documentation in our files or evidence of direct

effects of acute bee paralysis on B. franklini.

Deformed wing virus (DWV) is a honey bee pathogen that results in crippled and deformed

wings. DWV was thought to only affect honey bees, until 2004, when dead Bombus terrestris

and B. pascuorum queens with deformities resembling those in honey bees were observed. Some

virus has been shown to be transmitted from honey bees to bumble bees (Singh et al. 2010, p. 1;

Furst et al., 2014, p. 3). Tripodi (pers comm. 2016 in U.S. Fish and Wildlife Service 2016a, p.

42) notes that DWV has been detected in wild and commercially-sources bumble bees. Although

virological research focuses on honey bees, many of the 24 viruses isolated from honey bees

have a broad host range, infecting some Bombus species (Manley et al. 2015, p. 2). Commercial

bumble bee producers sometimes introduce young honey bees to nesting bumble bees queens to

stimulate egg-laying, and commercially raised bumble bee colonies are often fed pollen collected

by honey bees, thus providing a potential interface that exposes bumble bees to diseases carried

by the honey bees (Genersch et al. 2006, pp. 61-62). Infected bees with deformed wings are

unable to forage. Bumble bees that were observed with deformities were also not viable

(Genersch et al. 2006, p. 61). The Petition reports of unpublished personal observations of DWV

symptoms in commercially raised B. impatiens colonies in North America, but no research is

available to determine if other species of bumble bees are also susceptible to this disease (Xerces

Society and Thorp 2010, p. 17). While evidence exist that DWV does affect Bombus spp., we do

not have documentation in our files or evidence of direct effects of DWV on B. franklini.

Notwithstanding the studies postulating Nosema bombi spillover around commercial

greenhouses (such as Colla et al. 2006, entire), as well as the timing of commercialization and

Bombus declines, Szabo et al. (2012, p. 237) found that pathogen spillover in this form cannot

fully account for the Bombus declines. Malfi and Roulston (2014, p. 24) concluded that the

evidence linking N. bombi to the Bombus declines is correlative but does suggest species

undergoing range reductions are more susceptible to N. bombi infections, while noting that it is

nonetheless possible that elevated levels of N. bombi are natural in host species. Several experts

have surmised that N. bombi may not be culpable (or the only culpable) pathogen in the

precipitous decline of wild Bombus in North America (e.g., D. Goulson pers. comm. 2016, J.

Strange and A. Tripodi (USDA) pers. comm. 2016 in U.S. Fish and Wildlife Service 2016a,

p.41). Cameron et al. (2011b, p. 662) sum up the likelihood of pathogen spread being a primary

cause of Bombus declines by stating that higher pathogen prevalence and reduced genetic

diversity are realistic predictors of patterns of decline in North American bumble bees, although

cause and effect remain uncertain.

Known pathogens occur within the historical range of Bombus franklini, and we have evidence

of several pathogens infecting closely related species within that range. Although we have no

direct evidence of pathogens playing a role in the decline of B. franklini, the disappearance of B.

franklini occurred soon after a period of potential exposure to introduced pathogens, particularly

Nosema bombi which is known to have a more severe impact on rare species like B. franklini.

Decline of other closely related pollinators has been associated with these pathogens and it is

highly likely the factor has had some negative influence on the health of B. franklini populations.

3.1.2 Pesticides

Bumble bee exposure to pesticides can occur from direct spray or drift (Johansen and Mayer

1990), or from gathering or consuming contaminated nectar or pollen (Morandin et al. 2005, p.

619). Lethal and sublethal effects on bumble bee eggs, larvae, and adults have been documented

for many different pesticides under various scenarios (Kevan 1975, p. 301; Johansen 1977, p.

178; Plowright et al. 1978, p. 1145; Plowright et al. 1980, p. 765; Kearns and Inouye 1997, p.

302; Kearns et al. 1998, p. 91–92; Kevan 1999, p. 378; Thompson 2001, p. 305; Gels et al. 2002,

p. 722; Morandin et al. 2005, p. 619; Mommaerts et al. 2006, p. 752; Goulson et al. 2008, pp.

11.4–11.5). Documented sub-lethal effects to individual bumble bees and colonies include

reduced or no male production (Fauser-Misslin et al. 2014, pp. 453-454; Feltham et al. 2014, p.

320; Gill et al. 2012, p. 107; Mommaerts et al. 2006, pp. 3-4; Mommaerts et al. 2010, pp. 211-

212; Scholer and Krischik 2014, p.7), reduced or no egg hatch (Elston et al. 2013, pp. 6-7;

Mommaerts et al. 2006, pp.3-4), reduced queen production (Fauser-Misslin et al. 2014, pp. 453-

454; Feltham et al. 2014, p. 320; Whitehorn et al. 2012, p. 352), reduced queen longevity

(Fauser-Misslin et al. 2014, pp. 453-454), reduced colony weight gain (Feltham et al. 2014, p.

320; Whitehorn et al. 2012, p. 351; Scholer and Krischik 2014, p. 6), reduced brood size (Elston

et al. 2013, p. 6; Feltham et al. 2014, p. 320; Gill et al 2012, p. 107; Laycock et al. 2012, p. 3),

reduced feeding (Fauser-Misslin et al. 2014, pp. 453-454; Feltham et al. 2014, p. 320; Gill et al.

2012, p. 107; Gill and Raine 2014, pp. 211-212; Scholer and Krischik 2014, p. 5; Thompson et

al. 2014, pp. 2-3), impaired ovary development (Laycock et al. 2012, pp. 4-5), and an increased

number of foragers or foraging trips or duration (interpreted as risky behaviors) (Gill et al. 2012,

p. 107; Gill and Raine 2014; pp. 5-8; Feltham et al. 2014, p. 320).

Studies have also found evidence of adverse impacts to bumble bee habitat associated with

pesticides due to changes in vegetation and the removal or reduction of flowers needed to

provide consistent sources of pollen, nectar, and nesting material (Johansen 1977, p. 188;

Plowright et al. 1978, p. 1145; Williams 1986, 54; Kearns and Inouye 1997, p. 302; Smallidge

and Leopold 1997, p. 264; Kearns et al. 1998, p. 91–92; Shepherd et al. 2003). Declines in

bumble bees in parts of Europe have been at least partially attributed to the use of pesticides

(Williams 1986, p. 54; Kosior et al. 2007, p. 81).

Although the use of land for agricultural purposes has traditionally involved the use of pesticides

and other products toxic to bees, one particular class of insecticides known as neonicotinoids

have been strongly implicated in the decline honey bees worldwide as well as several Bombus

species, due to the contemporaneous introduction of neonicotinoid insecticides and the

precipitous decline of those species (Pisa et al. 2015, p. 69; Goulson 2013, p. 7-8; Colla and

Packer 2008, p. 10). Neonicotinoids are based on nicotine compounds; they are systemic

insecticides that act as a neurotoxin and varying levels of toxicity, affecting the central nervous

system of insects. Laboratory data indicated that neonicotinoids kill insects by interfering with

the receptors of the insects’ nervous system, causing overstimulation, paralysis, and death. The

neonicotinoid family of insecticides includes acetamiprid, clothianidin, imidacloprid,

nitenpyram, nithiazine, thiacloprid and thiamethoxam. They are used in a wide variety of

agricultural applications.

Imidacloprid became widely used in the United States starting in the early 1990s, followed by

clothianidin and thiamethoxam in the early 2000s (Douglas and Tooker 2015, pp. 5091-5092).

As of 2013, nearly all corn planted in the United States was treated with neonicotinoids and

various fungicides (Stokstad 2013, p. 675) and as of 2014 approximately one-third of the

soybean acreage in the United States was planted with neonicotinoid-coated seeds (Douglas and

Tooker 2015, p. 5090; U. S. Geological Survey National Pesticide Synthesis 2016). Imidacloprid

is one of the most widely used insecticide in the world (Yamamoto and Casida 1999).

Most studies examining the effect of neonicotinoids on bees have been conducted using the

European honey bee (Apis mellifera), and a handful of Bombus species including B. terrestris, B.

impatiens, and B. affinis (Lundin et al. 2015, p. 7), but there have been no studies on B. franklini

(Lundin et al. 2015, p. 7). We infer, however, that studies of the effect of pesticides to other

Bombus species will likely reflect their effects on B. franklini because these species have similar

life history traits (e.g., generalist foragers collecting pollen from same food sources). Bumble

bees may, in fact, be more vulnerable to pesticide exposure than honey bees. Bumble bees are

more susceptible to pesticides applied early in the year than are honey bees, because for one

month every year the entire bumble bee population depends on the success of the queens to

forage and establish new colonies. Also, because most bumble bees have smaller colonies (N=~

several hundred to a thousand) than honey bees (N=~30,000), a single bumble bee worker is

more important to the survival of the colony than a single honey bee worker (Thompson and

Hunt 1999, p. 155; Sponsler et al.. 2017, p. 30). Furthermore, since bumble bees nest

underground, they are additionally exposed to pesticide residues in the soil, specifically when the

application of a pesticide overlaps with colony establishment in the spring (Arena and Sgolastra

2014, p. 333). Moreover, bumble bee larvae consume large amounts of unprocessed pollen, and

therefore, are much more exposed to pesticide residues in pollen (Arena and Sgolastra 2014, p.

333).

Studies (e.g., Piiroinen and Goulson 2016, entire) are now emerging that have simultaneously

documented effects to bumble bees and honey bees at field-realistic levels. As generalist

foragers, both honey bees and bumble bees are often collecting from the same pollen sources (E.

Evans, pers. comm. 2016, in U.S. Fish and Wildlife Service 2017, p. 45). Based on detected

concentrations in the wild and the results of toxicity test, as well as the frequency of hives across

the landscape, Sanchez-Bayo and Goka (2014, pp. 12-14) predicted that exposure to

thiamethoxam, imidacloprid, and clothianidin (along with two organophosphates--phosmet and

chloropyrifos) pose the greatest risk to honey bees at a global scale. However, the additive and

synergistic effects of exposure to multiple pesticides and multiple times may exacerbate the

toxicity of exposure to any single pesticide, and thus, additional pesticides in combination with

others, may pose risks to bees as well. Several studies have revealed that bees are often

chronically exposed to a cocktail of pesticides throughout their lifetime (Sanchez-Bayo and Goka

2014, p. 5; Chauzat et al. 2006, pp. 256-257; Mullin et al. 2010, pp. 3-8; Krupke et al. 2012, pp.

3-5). For example, Sanchez-Bayo and Goka (2014, p. 5) detected 161 different pesticides at

honey bee colonies.

The effects of chronic exposure to multiple pesticides are poorly understood and are not

regularly examined in risk assessments (Goulson 2016, p. 4), and thus, the toxicity results, may

underestimate the actual risks posed to bees. Furthermore, pesticide formulations typically

contain less than 50 percent active ingredients with the remainder being surfactants (surface

active agent that reduces the surface tension of water) and solvents (collectively, referred to as

adjuvants). As bees forage, they are exposed to many adjuvants as well as active ingredients

(Mullin et al. 2015, p. 7). Adjuvants, however, are not typically included in risk assessments that

are required for pesticide registration (Mullin et al. 2015, p. 2), and are therefore, less studied,

but can be as or more toxic to bees as the active ingredients (Mullin et al. 2015, p.4). For

example, bumble bees are highly susceptible to emulsifiers such as perfluorooctane sulfonic acid

(Mommaerts et al. 2011, pp. 450-452). Goodwind and McBrydie (2010, p.232) found that four

of 11 commercially available spray adjuvants were toxic to honey bees at field rates.

Furthermore, active ingredients and inert ingredients may interact synergistically, causing

impacts that would not occur by exposure to the active ingredients alone (Mullin et al. 2015, p.

3). Lastly, bees are exposed to a number of significant and interacting stressors (Goulson et al.

2015, entire), which can compound the effects of pesticides. Exposure to fungicides greatly

increased the toxicity of insecticides in honey bees (Schmuck et al. 2003, pp. 82-85; Iwasa et al.

2004, p. 376; Piling and Jepsen 1993, pp. 295-296; Mullin et al. 2015, p. 4). Honey bees exposed

to fungicides had reduced colony nutrition and higher virus levels to fungicides (DeGrandi-

Hoffman et al. 2015, pp. 2523-2524). Pettis et al. (2013, p. 4), for example, found increased

probability of Nosema infection in honey bees feeding on pollen with high fungicide loads.

Several studies found exposure to insecticides reduced resistance to diseases (Fauser Misslin et

al. 2014, pp. 454-455, Pettis et al. 2013, p. 4), and exposure to dietary related stresses (e.g.,

short-term starvation) reduced the ability of bees to cope with toxins (Brown et al. 2000, p. 424;

Tyler et al. 2006, p. 2; Moret and Hempel 2000, p. 1167). Piiroinen and Goulson (2016, pp. 3-5)

found that exposure to N. ceranae reduced learning in honeybees and bumble bees, but both

species reacted differently to the combination of pathogen plus pesticide exposure.

Determining the extent of bee fatality caused by pesticides is difficult due to the myriad of other

potential stressors (e.g., pathogens, parasitoids, and diseases) and possible synergistic effects of

these sources. There are known instances where neonicotinoids such as clothianidin have adverse

effects to immunity and promote replication of viral pathogens in bees (e.g., DiPrisco et al. 2013,

p. 3). The interruption or disruption of endocrine functions is related to the function of species’

immune systems and the application of neonicotinoids may exacerbate the effects of pathogens.

To assess the perceived cause and effect relationship between neonicotinoid application levels

and Bombus franklini declines, we gathered available data on pesticide use for a subset of

chemicals and charted the application trend over time throughout the range of B. franklini.

Specifically, using pesticide application rate data collected from 1995 to 2015 (United States

Geological Survey National Pesticide Synthesis, accessed November 2017), we examined the

trend in use of three prevalent neonicotinoids; imidacloprid, clothianidin, and thiamethoxam over

time in 5 counties with recent (since 1995) B. franklini occurrences. Limited information on

neonicotinoid application in California is available in this dataset, so in addition we received data

from the California Pesticide Information Portal (accessed December 2017). All three chemicals

were added for each year to get a total application rate of imidacloprid, clothianidin, and

thiamethoxam combined. While we chose to focus these trend analyses on three commonly used

and studied neonicotinoids, we recognize that there are a myriad of pesticides, inactive

ingredients, and other chemicals that have documented negative effects on bees (as discussed

above) and could be similarly analyzed for application rate trends in our study area. Furthermore,

the vast majority of neonicotinoids are used as seed treatments on grains and other field crops

(Oregon Department of Agriculture 2018, pers. comm.). The National Pesticide Synthesis data

are both a high and low estimate of application rates based on the best available data – see

Appendix 3 for more information on the sources, assumptions, and use limitations of the data.

We also recognize that the timing, location, and methods of pesticide application play a role in

their effectiveness on target species (i.e., aerial spraying of row crops vs. placement of ant traps).

For our study area (Jackson, Douglas, and Josephine Counties in Oregon as well as Trinity and

Siskiyou Counties in California), the first reported use of Imidacloprid was in 1996;

thiamethoxam first reported in 2001, and clothianidin in 2004. Total estimated neonicotinoid

applications increased from 53.35 pounds/acre (24.19 kilograms/acre) in 1996 to 1,144.128

pounds/acre (518.86 kilograms/acre) in 2014.

While the rapid decline of Bombus franklini observations occurred shortly after the introduction

of neonicotinoid pesticide use within the historic range of the species, the exponential growth of

neonicotinoid applications starting in 2011 took place five years after the last observation of the

species so it is unlikely that the introduction and use of neonicotinoid pesticides alone can

account for the decline in B. franklini. There have been no studies on the effects of pesticide use

on B. franklini, no documented discoveries of any B. franklini injured or killed by pesticides.

Furthermore, the species is a habitat generalist and is not known to have a close association with

agricultural lands so it may have less exposure to pesticides than some other Bombus species.

However, pesticide use does occur in the range of B. franklini and confirmed effects to honey

bees and other Bombus species suggests that pesticide use could have been a factor in the decline

of B. franklini. The similarity in foraging traits that B. franklini has with both honey bees and the

other Bombus species (e.g., generalist foragers collecting pollen from similar food sources)

allows us to infer that that B. franklini would suffer exposure to and impacts from pesticides in

similar measure to other Bombus species when B. franklini is in areas where pesticides are

applied.

3.1.3. Habitat Loss and Degradation

Habitat loss and degradation was identified by the Petitioners as a threat contributing to the

decline of Bombus franklini (Xerces Society and Thorp 2010, p. 4). Habitat loss and degradation

can be manifest in many forms over different spatial and temporal scales. In this section we look

at habitat loss and degradation in the range of B. franklini and its potential effects on the species

through agricultural intensification, natural and introduced fire, and urbanization; livestock

grazing and climate change are discussed later in separate sections.

Conversion of natural habitat that is rich in flowers to farmlands, urban and suburban areas, and

other uses is a primary cause of bumble bee habitat loss (Goulson et al. 2015, p.2). Agricultural

intensification can result in habitat loss for bumble bees, as these practices often result in the

planting of monocultures, which tend to provide floral resources for a limited period of time,

rather than throughout the colony life cycle. Studies have confirmed that agricultural

intensification can negatively impact wild bees by reducing floral resource diversity and

abundance (Johansen 1997, p. 177; Williams 1986, p. 57; Kearns et al. 1998, p. 89; Hines and

Hendrix 2005, p. 1477; Carvell et al. 2006, p. 481; Diekotter et al. 2006, p. 57; Fitzpatrick et al.

2007, p. 185; Kosior et al. 2007, pp. 81, 84-86; Ockinger and Smith 2007, pp. 50; Goulson et al.

2008, p. 11.1; International Union for Conservation of Nature 2009, p. 2; Le Feon et al. 2010, p.

143). Agricultural intensification was determined to be a primary factor leading to the local

extirpation and decline of Illinois bumble bees (Grixti et al. 2009, p. 75). An increase use of

herbicides often accompanies development and agricultural intensification, and the wide-spread

use of herbicides in agricultural, urban and even natural landscapes has led to decreases in

flowering plants (Potts et al. 2010, p. 350).

Douglas, Jackson and Josephine Counties in Oregon, and Siskiyou and Trinity Counties in

California, are generally characterized as rural, agriculturally based counties with large

proportions of public land and which lack the larger population centers found to the north and

south of the historical range of Bombus franklini. Information specific to agricultural

intensification within the historic range of B. franklini is not available at the spatial and temporal

scales needed to quantify this threat (United States Department of Agriculture – National

Agriculture Statistics Service, pers. comm. 2017). However, between 1997 and 2012, Oregon

saw a decrease in both the overall number of farms and ranches, as well as a decrease of more

than a million acres of land in agriculture (United States Department of Agriculture – National

Agriculture Statistics Service 2015, p. 6). Within the historic range of B. franklini, Douglas,

Jackson and Josephine Counties all saw a similar decrease of total acres in agricultural cropland,

as summarized in Table 4 below (United States Department of Agriculture – National

Agriculture Statistics Service, pers. comm. 2017). While the total number of acres of agricultural

cropland is not synonymous with agricultural intensification (specifically, the expansion of

monocultures), a decrease in total acres of agriculture leads us to conclude that agricultural

intensification is not likely a major threat to B. franklini. We have no documentation in our files

or any direct evidence that agricultural intensification has contributed to the decline of B.

franklini.

Table 4. Acres of Agricultural Cropland in Douglas, Jackson, and Josephine Counties in Oregon

Data: USDA-NASS 2015, 2017

Acres of Agricultural Cropland

1997

2002

2007

2012

Douglas

123,133

107,503

73,559

49,222

Jackson

71,251

67,762

56,530

32,765

Josephine

17,767

15,860

17,389

8,365

Oregon

1997

2002

2007

2012

Number of farms and ranches

39,975

40,033

38,533

35,439

Total land in agriculture

(millions of acres)

17.7

17.2

16.4

16.3

Forty-two percent of the sites where Bombus franklini have been located (18 of 43) occur on

federally owned land, primarily the U.S. Forest Service and Bureau of Land Management. This

notable proportion could be due to a good percentage of B. franklini occurring on Federal land or

simply that searches for B. franklini often occur on Federal land. Very little habitat on these

ownerships has been permanently altered or lost through development or agricultural

intensification.

Fire caused by both natural and manmade factors has been an important change agent on the

landscape in the range of Bombus franklini. Because fire reduces natural succession of forests

through the burning of encroaching woody plants, fire is a primary factor in the maintenance of

grassland and meadow habitat that supports Bombus species (Shultz and Crone 1998, p. 244;

Huntzinger 2003). With the increase in human development came fire suppression to limit

damage to manmade structures. Fire suppression allows woody encroachment to occur and the

diverse landscape created by fire (open areas mixed within forested areas) is being replaced by

increasing areas of denser forested habitat; the open areas that facilitated the growth of diverse

understory plant communities are greatly reduced from their historical condition (Ruchty 2011,

p. 26). Conifer species now cover much of the area that was previously open meadow habitat in

the range of B. franklini (Panzer 2002; Shultz and Crone 1998, p. 244). This loss of habitat by

fire suppression likely played some role in the decline if B. franklini by limiting the availability

and diversity of floral resources and nest and overwintering habitat. However, because there is

still healthy meadow habitat located in areas where B. franklini were previously found, we do not

believe that loss of habitat from fire suppression was a major factor in the decline of the species,

particularly the precipitous decline that occurred after 1998.

The increased fuel loads from fire suppression increase the potential for catastrophic, large scale,

and high temperature wildfires. Any Bombus colonies in the path of this type of fire would be at

risk of extirpation. Wildfire may have played a role in the decline of B. franklini by extirpating

some historical populations in the range, but we have no information confirming this. We have

no information that suggests that any known B. franklini occurrence sites were in the path of

catastrophic wildfires at the time they were occupied. Controlled burning became a management

tool for reducing potential fuel loads for wildfire; controlled burning and other fuel reduction

activities are carried out by Federal land management agencies including the US Forest Service

and Bureau of Land Management in the range of B. franklini. The effects of fire on invertebrates

depends greatly on the biology of the specific taxa (Gibson et al. 1992) and in the case of B.

franklini, controlled burns could certainly cause death of individual bees and negative effects to a

colony. However, we have no information to indicate that controlled burns were a factor in the

decline of B. franklini.

Ongoing urbanization also contributes to the loss and fragmentation of natural habitats. Urban

gardens and parks may provide habitat for some pollinators including bumble bees (Frankie et al.

2005, McFrederick and LeBuhn 2006) but they tend not to support the species richness of

bumble bees that can be found in nearby undeveloped landscapes (Xerces Society and Thorp

2010, p. 13), or that which was present historically (McFrederick and LeBuhn 2006). Bombus

franklini and B. occidentalis have both been observed in urban areas of Ashland, Oregon, but not

since 2002. A study in Boston, Massachusetts, concluded that human built structures, such as

roads and railroads, can fragment plant populations and restrict bumble bee movement

(Bhattacharya et al. 2003, p. 37). Urban development may also lead to direct mortality, i.e.

through vehicle collisions (Goulson et al 2015, p. 2). Another study of the factors adversely

affecting bumble bees and cuckoo bees in Europe found the expansion of urban areas to be an

important driver of pollinator loss in approximately half of the countries examined (Kosior et al.

2007, p. 81).

Table 5 shows the 1995 and 2017 populations for Douglas, Jackson, and Josephine Counties, as

well as the population for Ashland, OR. Table 5 also shows the population growth estimates that

were completed in 2015 for each of the counties.

Table 5. Human population growth estimates for Douglas, Jackson, and Josephine Counties in

Oregon and Ashland, Oregon.

1995 population

2017 population*

2035 estimate

2065 estimate

Douglas County

98,820

111,180

129,910

152,910

Jackson County

167,330

216,900

246,575

306,575

Josephine County

71,290

85,650

99,720

121,720

Ashland, Oregon

17,985

20,700

*2017 data preliminary

For Bombus in general, loss and degradation of habitat is known to reduce both bee diversity and

abundance (Potts et al. 2010, p. 348-349). Habitat fragmentation can alter pollinator community

composition, change foraging behavior of bumble bees, and reduce bee foraging rates, and is

believed to be one of the factors contributing to the decline of several bumble bee and cuckoo

bee species in Europe (Kearns and Inouye, 1997, p. 299; Ockinger and Smith 2007, p. 50;

Rusterholz and Baur 2010, p. 148; Kosior et al 2010, pp. 81). Bumble bees have been found to

be susceptible to the disruption of healthy metapopulation structures due to fragmentation, and

may decrease source populations of bumble bees for recolonization (National Research Council

2007, p. 93; Goulson et al. 2008, p. 11.7). Other studies have suggested that fragmented bumble

bee populations can suffer from inbreeding depression as a result of geographic isolation (Darvill

et al. 2006, p. 601, Goulson et al. 2008, p. 11.7) (see sections 2.2.2 and 3.1.6 for more on genetic

impacts from small population sizes).

Although habitat loss and fragmentation has established negative effects on bumble bees

(Goulson et al. 2008; Williams and Osborne 2009, pp. 371-373), many feel it is unlikely to be a

main driver of the recent, widespread North American bee declines (Szabo et al. 2012, p. 236;

Colla and Packer 2008, p. 1388; Cameron et al. 2011b, p. 665). Further, habitat remains

generally intact and in good condition throughout the known historic Bombus franklini locations

and all of the recent focused survey areas, with the notable exceptions being the creation of Lake

Applegate upon the completion of Applegate Dam in the fall of 1980 and a report of soil

modification on a portion of the Gold Hill site. The Applegate Dam project inundated two

historic B. franklini locations (Copper and 2 miles north of Copper), with historic observations

from 1963 and 1968 (Xerces Society and Thorp 2010, p. 13; Thorp, pers. comm. 2017). The

Petition noted that in 2004, soil had been excavated and deposited in a portion of the Gold Hill

area (Xerces Society and Thorp 2010, p. 13). The last observation of B. franklini at Gold Hill

was in the year 2000, and the site was revisited 14 times over the next three years with no

observations of the species. At both Lake Applegate and Gold Hill, we don’t know if the species

was still using the habitat by the time the activities took place. Overall, many feel that habitat

loss and fragmentation are not a main driver of the decline of B. franklini, particularly since

many other Bombus species have been recorded in the habitat where searchers have looked for B.

franklini (Thorp, pers. comm. 2017; Godwin, pers. comm. 2017; Colyer, pers. comm. 2017).

3.1.4 Livestock Grazing

Livestock grazing occurs on public land on much of the historic range of Bombus franklini. The

Petition stated that livestock grazing may adversely impact bumble bee populations by: (1)

depleting food resources (Morris 1967, p. 472; Sugen 1985, p. 299; Kruess and Tscharntke

2002b, p. 1570; Vazquez and Simberloff 2003, p. 1081; Hatfield and LeBuhn 2007, p. 150); (2)

trampling nesting sites (Sugden 1985, p.299); and (3) negatively impacting ground-nesting

rodents (Johnson and Horn 2008, p. 444; Schmidt et al. 2009, p. 1), which may in turn reduce the

number of nest sites available for bumble bees (Xerces Society and Thorp 2010, p. 13). The

Petition also stated that livestock grazing has differing impacts on flora and fauna based on the

type, habitat, intensity, timing and length of grazing (Gibson et al. 1992, p. 174; Carvell 2002, p.

44; Kreuss and Tscharntke 2002a, p. 293; Kruess and Tscharntke 2002b, p. 1577; Xerces Society

and Thorp 2010, p. 13). Several studies of livestock grazing impacts on bees suggest increased

intensity of livestock grazing affects the species richness of bees (Morris 1967, p. 473; Sugden

1985, p. 309; Vazquez and Simberloff 2003, p. 1080; Hatfield and LeBuhn 2007, p. 156). In

contrast, one study cited in the Petition suggests that grazing, especially by cattle, can play a key

positive role in maintaining the abundance and species richness of preferred bumble bee forage

(Carvell 2002, p. 44).

Overgrazing by sheep between 1890 and 1920, resulted in trampling vegetation and denuding

soils, and is currently evident today in the continuing erosion of the granitic soils of the

McDonald Basin, Siskiyou Gap, Mt. Ashland, and the Siskiyou Crest (LaLande 1995, p. 31; T.

Atzet, Siskiyou Field Institute, Selma, Oregon, pers. comm. 2017). While sheep overgrazing

likely has degraded B. franklini habitat, we have no specific information on the effects of this

habitat loss and fragmentation. Evidence of livestock grazing has been observed interspersed

within abundant floral resources in B. franklini habitat during several recent targeted survey

efforts (Brooks 1997 pers. comm.; U.S. Fish and Wildlife Service 2016; U.S. Fish and Wildlife

Service 2017; P. Trail, U. S. Fish and Wildlife Service, Ashland, Oregon, pers. comm. 2017).

However, no specific information is available on the impacts of livestock grazing on B. franklini

making it impossible to connect the activity to any specific species response. The number of

grazing allotments have decreased on The Rogue-River Siskyou NF, particularly on the Siskiyou

Mountains Ranger District (Applegate) in the last 20 years; the grazing on High Cascades

Ranger District (near Prospect, OR), have not changed in the last 20 years (J. von Kienast, pers.

comm. 2018). Generally the dates that cows are on the allotments start on June 15

and stay on

until October but dates vary by allotment. Most of the locations for B. franklini on the Rogue

River-Siskiyou NF overlap with grazing allotments. Cattle grazing has been observed at all

Bombus survey locations on the High Cascades Ranger District. (S. Colyer pers. comm. 2018).

Outside of these areas, we have no new information that the timing, location, intensity, or

duration of grazing has changed, with the exception of the Cascade-Siskiyou National

Monument, where most grazing has been retired on the Cascade-Siskiyou National Monument

(Trail, pers. comm. 2017) (See Figure 1).

3.1.5 Climate Change

Global climate change was identified in the Petition as a threat to Bombus franklini (Xerces

Society and Thorp 2010, pp. 20-21). Climate change may cause shifts in the range of host plant

species, which can be especially detrimental to dependent pollinators when combined with

habitat loss (Xerces Society and Thorp 2010, p. 20; Schroeder, pers. comm. 2017). Specific

impacts of climate change on pollinators are not well understood; most of the existing

information on climate change impacts to pollinators comes from studies on butterflies – studies

specifically relating to bumble bees are scant, and we found no climate change information

specific to B. franklini.

Climatic changes in temperature, precipitation, and the increased frequency of storm events

(Intergovernmental Panel on Climate Change 2013, entire) can affect population sizes directly,

affecting survival and reproduction (Bale et al. 2002, p. 11; Roland and Matter 2016, p. 22).

These climatic changes can also affect populations indirectly, by altering resource availability

and species interactions (Boggs and Inouye 2012, p. 505; Hoye et al. 2013, p. 762; Kudo and Ida

2013, p. 2319). Some studies suggest that bumble bee populations are responding to climate

change with recent latitudinal and elevational range shifts (Ploquin et al 2013, p. 9; Pyke et al

2016, p. 11). Some bumble bee populations are active earlier in the season than in the past

(Bartomeus et al 2011, p. 20646). Ogilvie et al. (2017, p. 1) found that bumble bee abundances

were driven primarily by the indirect effects of climate on the temporal distribution of floral

resources.

The changes in climate likely to have the greatest effects on bumble bees in general include

increased drought, increased flooding, increased storm events, increased temperature and

precipitation events, early snow-melt, late frost, and increased variability in temperature and

precipitation. These climate changes may lead to decreased resource availability (due to

mismatches in temporal and spatial co-occurrences), decreased availability of nesting habitat

(due to higher temperatures), and increased pressures from pathogens and non-native species

(Goulson et al. 2015, p. 4; Goulson, pers. comm. 2016 in U.S Fish and Wildlife 2016, p. 52; Kerr

et al. 2015, pp. 178-179; Potts et al. 2010, p. 351; Cameron et al. 2011a, pp. 35-37; Williams and

Osborne 2009, p. 371).

Climate variability may lead to range shifts, such that there is spatial mismatch among plants and

their pollinators (Memmott et al. 2007, p. 712). While this has been demonstrated in butterflies

(Forister et al. 2010, pp. 2088-2089; Hickling et al. 2006, p. 452), it may be less of a factor for

bumble bees. As generalist foragers, they do not require synchrony with a particular plant

species. However, elevational range shifts have been documented in some bumble bees (e.g.,

Pyke et al. 2016, pp. 8-10; Kerr et al 2015, p. 179). Temporal mismatches may be more of an

issue for bumble bees due to their long active season, during which they require consistent access

to floral resources. Floral resource availability in early spring is particularly crucial for bumble

bees, as that is when they first emerge and initiate nests. Thus, temporal asynchrony could lead

to diminished resource availability at times that are critical to bee development and colony

success. Other potential effects from climate change include increased flooding and storm

events, which may directly reduce available nesting habitat and hibernating habitat by inundating

those areas (Goulson et al. 2015, p. 4). Changes in rodent populations due to climate change may

also reduce nesting habitat, as bumble bees often use rodent burrows as nesting areas.

Furthermore, bumble bees are poorly adapted to high temperatures, and thus are vulnerable to

increased stress from overheating.

Several of the targeted Bombus franklini and B. occidentalis survey reports between 2015 and

2017 include mention of widespread hot, dry climate affecting timing and abundance of floral

resources during the surveys (Bureau of Land Management 2015; Trail, pers. comm. 2017),

indicating that at least at local scales in recent years, changing climate conditions may have

affected resources available to Bombus colonies. Although the Olgilvie et al. study as well as the

survey reports suggest potential indirect effects of climate change on Bombus, we have no

information to indicate that the effects of climate change were connected to the decline of B.

franklini; numerous Bombus species persist in areas considered to maintain good quality habitat

for B. franklini (Pool 2014, entire; Colyer 2016, entire).

3.1.6 Small Population Dynamics

Small population size has been identified as a threat to Bombus franklini. The Petition (Xerces

Society and Thorp, p. 20) states that B. franklini is rare and has always had very small

populations (relative to other similar, native bumble bees in the western United States), and

likely have low genetic diversity, making the species more vulnerable to habitat change or loss,

parasites, diseases, stochastic events, and other natural disasters such as droughts (Xerces

Society and Thorp 2010, p. 20).

As stated in section 2.1.2, between 1998 and 2006, the number of Bombus franklini observations

declined from a high of 98 at 8 locations, to a lone individual in 2006. No observations of B.

franklini have occurred since 2006 despite an increase in the survey effort.

As mentioned in section 2.2.2, bumble bees exhibit a haplodiploidy sex determination system. In

these systems, unfertilized (haploid) eggs become males that carry a single set of chromosomes,

and fertilized (diploid) eggs become females that carry two sets of chromosomes. This may

result in lower levels of genetic diversity than the more common diploid-diploid sex

determination system, in which both males and females carry two sets of chromosomes.

Haplodiploid organisms (such as bumble bees) may be more prone to population extinction than

diploid-diploid organisms, due to their susceptibility to low population levels and loss of genetic

diversity (Packer and Owen 2001, p. 26; Zayed and Packer 2005, p. 10742; Darvill et al. 2006, p.

601, Ellis et al. 2006, 4375; Goulson et al. 2008, p. 11.7-11.9). Inbreeding depression in bumble

bees can led to the production of sterile diploid males (Goulson et al. 2008, p. 11.7) and has been

shown to negatively affect bumble bee colony size (Herrman et al. 2007, p. 1167), which are key

factors in a colony’s reproductive success. Diploid male production has been detected in

naturally occurring populations of bumble bees, and recent modeling work has shown that

diploid male production, where present, may initiate a rapid extinction vortex (a situation in

which genetic traits and environmental conditions combine to lead a species to extinction)

(Goulson et al. 2008, p. 11.8). Bombus franklini is a haplodiploid organism with a relatively

small population size compared to other Bombus species. A haplodiploid genetic system makes

bees very vulnerable when populations get small because of inbreeding and the production of

sterile males (Colla, 2018, pers. comm.). Although we have no direct evidence that small

population size or a rapid extinction vortex contributed to the decline of the species, the genetic

system and historically small population size of B. franklini likely heightened the species’

vulnerability to other stressors in the environment.

3.1.7 Competition from non-native bees

The European honey bee (A. mellifera), was first introduced to eastern North America in the

early 1620s, and introduced to California in the early 1850s (Xerces Society and Thorp, p.21).

The resources of A. mellifera and native Bombus species may overlap resulting in the potential

for increased competition for resources (Thomson 2004, p. 458; Thomson 2006, p. 407;

Thomson 2016, p. 1247). Decreased foraging activity and lowered reproductive success of

Bombus colonies have been noted near A. mellifera hives (Evans 2001, p. 32–33; Thomson 2004,

p. 458; Thomson 2006, p. 407). Additionally, the size of workers of native Bombus species were

noticeably reduced where A. mellifera were present, which may be detrimental to Bombus colony

success (Goulson and Sparrow 2009, p. 177). As noted in the 2010 Petition, is likely that the

effects discussed in these studies are local in space and time, and most pronounced where floral

resources are limited and large numbers of commercial A. mellifera colonies are introduced

(Xerces Society and Thorp, p. 21). We could not find information to indicate that any area of B.

franklini habitat in the range of the species has limited floral resources and large numbers of A.

mellifera. We have no information related to the specific placement of commercial honey bee

colonies in or near B. franklini habitat. Furthermore, A. mellifera have been present without

noticeable declines in Bombus populations over large portions of their ranges (Xerces Society

and Thorp, p. 21) and we have no new information that connects competition from A. mellifera

to the decline of B. franklini, particularly the noticeable decline after 1998.

There is potential for non-native commercially raised bumble bees to naturalize and outcompete

native bumble bees for limited resources such as nesting sites and forage areas. Five

commercially reared Bombus impatiens workers and one queen were captured in the wild near

greenhouses where commercial bumble bees are used, suggesting this species may have

naturalized outside of its native range. In this study, B. impatiens, which has a native range in

eastern North America, was detected in western Canada (Ratti and Colla 2010, pp. 29–31). A

study in Japan found that non-native B. terrestris colonies founded by bees that had escaped

from commercially produced colonies had over four times the mean reproductive output of

native bumble bees (Matsumura et al. 2004, p. 93). A study in England found that commercially

raised B. terrestris colonies had higher nectar-foraging rates and greater reproductive output than

a native subspecies of B. terrestris (Ings et al. 2006, p. 940). The 2010 Petition noted that B.

impatiens colonies were imported to pollinate agricultural crops and strawberries in Grants Pass,

Oregon, in the range of B. franklini (Xerces Society and Thorp, p. 18). Although non-native

Bombus species in the range of B. franklini could outcompete B. franklini for floral resources and

nesting habitat, we could not find any information to definitely connect competition with non-

native bumble bees to the decline of B. franklini. Furthermore, invertebrate surveys in B.

franklini habitat continue to show evidence of healthy populations of other native Bombus

species unaffected by competition from non-native bees (Pool 2014, entire; Colyer 2016, entire).

3.2 Synergistic Effects

It is likely that several of these risk factors are acting additively and synergistically on Bombus

species (Goulson et al. 2015, p. 5) and the combination of multiple stressors is likely more

harmful than a stressor acting alone (Gill et al. 2012; Coors and DeMeester 2008; Sih et al.

2004). There is recent evidence that the interactive effects of pesticides and pathogens could be

particularly harmful for bumble bees (Fauser-Misslin et al. 2014, pp. 453-455; Baron et al. 2014,

pp. 463-465) and other bees (Alaux et al. 2010, pp. 775-777; Pettis et al. 2012, pp. 155-156;

Vidau et al. 2011, pp. 3-5; Aufavre et al. 2012, pp. 2-3). Nutritional stress may compromise the

ability of bumble bees to survive parasitic infections as evidenced by a significant difference in

mortality in bumble bees on a restricted diet than well fed bees infected with Crithidia bombi

(Brown et al. 2000, pp. 424-425). Bumble bees with activated immunity may have metabolic

costs, such as increased food consumption (Tyler et al. 2006, p. 2; Moret and Schmid-Hempel

2000, pp. 1166-1167). Additionally, exposure to pesticides may increase with increased food

consumption in infected bees (Goulson et al. 2015, p. 5). There is evidence that activating

immunity impairs learning in bumble bees (Riddelland Mallon 2006, Alghamdi et al. 2008, p.

480). Impaired learning is thought to reduce the ability of bees to locate floral resources and

extract nectar and pollen, therefore, exacerbating nutritional stresses (Goulson et al. 2015, p. 5).

Further, evidence of the relationship between low genetic diversity and disease susceptibility was

discussed in Cameron et al. (2011b, p. 665), who stated that declining North American species

with low genetic diversity have higher prevalence of the pathogen N. bombi. Therefore,

pathogens in combination with pesticides, and pathogens in combination with the effects of small

population size likely hastened and amplified the decline of B. franklini to a greater degree than

any one of the three factors would cause on its own.

3.3 Beneficial Actions

We are aware of no conservation efforts or beneficial actions specifically taken to address the

stressors to Bombus franklini. Oregon does not include invertebrates on their state endangered

species list (ODFW 2018) and California has no bees on its list of Threatened and Endangered

Invertebrates (CDFW 2018). California has the species listed on its list of Terrestrial and Vernal

Pool Invertebrates of Conservation Priority but has no required actions or special protections

associated with the listing (CDFW 2017, p. 10). Bombus franklini is on the species index for the

U.S. Forest Service and Bureau of Land Management Interagency Special Status /Sensitive

Species Program (ISSSSP) (ISSSSP 2018). Though the agencies do include the species in survey

efforts and conduct general meadow enhancement activities like reducing conifer encroachment,

there are no actions resulting from the ISSSSP classification that reduce or ameliorate known

threats to B. franklini.

The U.S. Forest Service is working to include a section in all biological evaluations to address

the effects from agency actions on pollinators. In addition, the Rogue River-Siskiyou National

Forest is currently implementing projects and mitigations to create and enhance pollinator habitat

(S. Colyer, pers. comm. 2018) The Oregon Department of Agriculture restricts some potential

sources of N. bombi from entering the state for agricultural uses, including commercially-

produced colonies of Bombus impatiens; only Bombus species native to Oregon are permitted for

commercial pollination purposes (Oregon Department of Agriculture 2017, p. 5). California does

however allow for the importation of B. impatiens, and other species such as the Blue Orchard

Bee (Osmia lignaria) for pollination services with appropriate permits in both Oregon and

California (California Department of Food and Agriculture 2017; Oregon Department of

Agriculture 2017).

General awareness of honey bee colony losses and increase of conservation efforts for

pollinators in general has likely had limited, indirect effects. Stemming from this general

awareness is a reduction in the use of some pesticides throughout North America. Some local

municipalities have enacted legislation against aerial pesticide applications but similar efforts

have not been adopted at the state or range-wide scales (Powell 2017, p. 1; City of Portland

2015, p. 2). However, in the 2017 legislative session, Oregon passed an Avoidance of Adverse

Effects on Pollinating Insects law (ORS 634.045) that is providing enhanced training of licensed

and unlicensed pesticide applicators in the state (A. Melathopoulos, pers. comm. 2018). In

January 2017, the U.S. Environmental Protection Agency’s Office of Pesticide Programs

published their Policy to Mitigate the Acute Risk to Bees from Pesticide Products, which

recommended new labeling statements for pesticide products including warnings for pesticides

with a known acute toxicity to bees including neonicotinoids (specifically including

imidacloprid, clothianidin, and thiamethoxam) (United States Environmental Protection Agency

2017, p. 31). In addition, EPA is working with state and tribal agencies to develop and

implement local pollinator protection plans, known as Managed Pollinator Protection Plans

(MP3s). EPA is promoting MP3s to address potential pesticide exposure to bees at and beyond

the site of the application. However, states and tribes have the flexibility to determine the scope

of pollinator protection plans that best responds to pollinator issues in their regions. For example,

state and tribal MP3s may address pesticide-related risks to all pollinators, including managed

bees and wild insect and non-insect pollinators (United States Environmental Protection Agency

2018).

4.0 Analysis of Current Condition

As described in section 1.2, we applied the conservation biology principles of resiliency,

representation, and redundancy (the 3Rs) as a framework to assess the viability of Bombus

franklini. For a species to sustain populations over time it needs a sufficient number and

distribution of viable populations to withstand environmental stochasticity (resiliency),

catastrophes (redundancy), and changes in its environment (representation). To assess resiliency

and redundancy, we evaluated the change in B. franklini occurrences (populations) over time. To

assess representation (as an indicator of adaptive capacity) of B. franklini, we evaluated the

spatial extent of occurrences over time.

Resiliency is the ability to sustain populations in the face of environmental variation and

transient perturbations. In section 2.2.3 we described that Bombus franklini requires the

following for resiliency: (1) populations with large N

, (2) sufficient floral resources in close

proximity to nesting and overwintering sites, (3) connectivity among colonies and populations,

and (4) spatial heterogeneity. Historically, the species has always been rare and has one of the

narrowest distributions of any Bombus species in the world. Even so, the abundance and

distribution of B. franklini has declined significantly (U.S. Fish and Wildlife Service 2018, pp.

10-14); the species has not been observed since 2006 despite an intensive survey effort in some

areas of the historical range. Prior to 1998, search efforts for the species were varied in timing,

scope, intensity, and methodology. During the more intensive surveys from 1998 until the last

observation in 2006, B. franklini was observed at 11 sites, including seven locations where it had

not been previously documented. In 1998, 98 bees were found among eight locations. Searchers

found fewer and fewer bees after that even though they continued extensive searches in multiple

locations with the highest likelihood of finding the species. Twenty bees were located in 1999,

nine individuals were observed in 2000, and one individual in 2001. Although 20 B. franklini

were observed in 2002, only three were observed in 2003 (all at a single locality), and a single

worker bee was observed in 2006. Despite continued intensive search efforts through 2017, there

have been no confirmed observations of B. franklini since 2006. There are currently no known

healthy B. franklini individuals and therefore no known healthy colonies or populations of B.

franklini. Despite the fact that some high quality habitat with diverse floral resources and

available nesting and overwintering sites appears to be available in the historic range of B.

franklini, no individuals of the species have been found in any habitat since 2006. The resiliency

of B. franklini has declined significantly since the late 1990’s.

Representation is the ability to adapt to changing environmental conditions; it is the species’

evolutionary capacity or flexibility. In section 2.2.3 we described that Bombus franklini requires

the following for representation: healthy populations distributed across areas of unique adaptive

diversity (i.e., ecoregions) to maintain evolutionary drivers (gene flow, natural selection, genetic

drift) to mimic historical patterns. Bombus franklini is rare and has always had very small

populations (relative to other similar, native bumble bees in the western United States), and

likely have low genetic diversity, making the species more vulnerable to environmental factors.

As a haplodiploid organism, B. franklini may be more prone to population extinction than

diploid-diploid organisms, due to its susceptibility to low population levels and loss of genetic

diversity. No B. franklini have been observed since 2006 despite an intensive survey effort and

therefore we cannot identify any current populations of B. franklini distributed across any level

of ecological conditions. The vulnerability resulting from B. franklini’s genetic system and the

loss in the spatial extent of its populations suggest the representation of B. franklini has declined

significantly since the late 1990’s.

Redundancy protects species against the unpredictable and highly consequential events for which

adaptation is unlikely. In section 2.2.3 we described that Bombus franklini requires the following

for redundancy: sufficient distribution to guard against catastrophic events wiping out portions of

the species adaptive diversity, i.e., to reduce covariance among populations, and an adequate

number of healthy populations to buffer against catastrophic losses of adaptive diversity. Bombus

franklini has the smallest geographic distribution of any North American bumble bee and

possibly the world (Williams 1998, as cited in Xerces Society and Thorp 2010, p. 6), and thus

likely had low redundancy prior to its decline. When we look at occurrence data for the species

and overlay it with our 6 km

grid estimating minimum habitat patch to estimate the number of

populations present on the landscape, we find that each site where B. franklini has ever been

observed could potentially reflect a population. Therefore, data allow us to estimate 43 potential

populations of B. franklini since records have been kept. From 1998 to 2006, 14 potential

populations could be identified and no B. franklini have been observed since 2006 despite a more

intensive survey effort in some areas of the historic range. We cannot identify any current

healthy populations distributed across any spatial extent. The losses in both the number of

populations and spatial extent indicate that the redundancy of B. franklini has declined

significantly since the late 1990’s.

5.0 Analysis of Future Condition

Due to the lack of observations of the species since 2006, we did not project anticipated future

states of resiliency, redundancy or representation. Numerous survey efforts for invertebrate

pollinators have occurred since 2006 in high quality habitat where Bombus franklini have been

historically observed. During these efforts by Xerces Society, USFS, BLM, FWS, classes at

Southern Oregon University and many private individuals, several species of Bombus have

consistently been observed, but B. franklini has never been found. Although the failure to detect

a species during surveys is not equivalent to a conclusive demonstration of its absence and may

simply reflect the very low detection probability for rare species, the certain losses in both the

number of populations and their spatial extent render B. franklini vulnerable to extinction even

without further external stressors acting upon the species.

Several conservation measures (as described in section 3.3) could be applied to important

Bombus habitats within the historic range of B. franklini, which would be beneficial to other

Bombus species (notably B. occidentalis) and any existing but unknown populations of B.

franklini. These include but are not limited to reductions in herbicide and pesticide applications

and restrictions on the importation and use of commercially produced bees. Expanded and

standardized surveys for B. franklini, B. occidentalis, and other special-status invertebrates

would improve knowledge of species abundance, distribution, and habitat conditions.

6.0 Literature Cited

Alaux, C., J. Brunet, C. Dussaubat, F. Mondet, S. Tchamitchan, M. Cousin, J. Brillard, A. Baldy,

L. P. Belzunces, and Y. Le Conte. 2010. Interactions between Nosema microspores and a

neonicotinoid weaken honey bees (Apis mellifera). Environmental Microbiology. 12(3):

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7.0 Appendices

Appendix 1: Occurrence Table

Appendix 2: Dear Interested Party Letter

Appendix 3: Neonicotinoid Pesticide Application Data by County, 1995-2015

Appendix 4: Expert Elicitation Questionnaire

Appendix1:OccurrenceTable‐Table1:KnownoccurrencesofBombusfranklini

Landowner 1923 1925 1930 1946 1949 1950 1952 1953 1958 1963 1964 1968 1969 1976 1980 1986 1988 1989 1990 1992 1994 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

UnknownLocation unknown 1W,1M

Sutherlin(3miWof) Private

1U

(1)

0(1) 0(1) 0(2) 0(1) 0(2) 0(3) 0(1)

Roseburg Private 1W 2M,1U

Ashland Private 2W 1U 1U

4Q,1W,

1Q

1U

Ashland(8miENE) Private 3W,6M

Ashland(Ashlandpond)

Cityof

Ashland

2W

Ashland(MistletoeRd) Private 0(1) 0(2) 1U(3) 0(4) 0(7) 0(5) 0(2)

Ashland(SOURocaCanyon)

State(no

publicaccess)

2Q

Buncom(Eof) Private

1U

(1)

0(3) 0(1) 0(1)

CentralPoint Private 2W

Copper USFS 7U

Copper(2miN) USFS 2M,2W

Copper(14miN) BLM 1W

Copper(8miWof) USFS 2U

Copper(nr‐see17mi.Wof

Ruch)

USFS

12Q(plus

207other

specimens)

GoldHill Private 1W 3W 1W 7W 12W

GoldHill(3miEof) Private

44U

(4)

0(2)

5U

(7)

0(7) 0(3) 0(4) 0(2) 0(4) 0(2) 0(2)

GrizzleyPeak BLM 1Q 0(2) 0(2) 0(1) 0(2) 0(2) 0(2) 0(2) 0(3) 0(1) 0(2)

Jacksoncampground USFS 2U(2) 0(2) 0(1) 0(1) 0(1)

KenneyMeadows BLM

3U

(2)

0(2) 0(2) 0(2) 0(1) 0(1) 0(1)

LostCreekReservoir Private 1Q 0(1) 0(1) 0(1) 0(1)

Medford Private 8W,10M 2W,1M

2Q,12W,

24M(7)

1M

5W,4

Medford(RoxyAnnPeak) Private 2Q

Mt.Ashland USFS

4W

(over2

days)

1Q(plus207

other

specimens)

37U

(3)

19U

(6)

2U

(7)

1U

(5)

19U

(10)

3U

(9)

0(13) 0(11)

1W

(8)

0(7)

Phoenix(Eof) Private 0(1) 0(2)

Ruch Private 6W 12W

3U

(3)

0(2)

1U

(2)

0(1) 0(2) 0(2)

Ruch(SSEof) Private 0(2)

1U

(3)

0(2) 0(1) 0(2) 0(1)

ShaleCityRdtoGrizzley

Peak

Private 1Q

UnionCreek USFS 1Q 0(1)

GrantsPass Private 3W(2)

Merlin Private 1W

Selma(Sof) Private

2U

(1)

0(1) 0(1)

Wonder(Wof)‐reportedas

historicalrecordbutnodate

ofoccurancerecord

reported

Private 0(1)

Hilt Private 1M 1Q 12W

2U

(2)

0(3) 0(3) 0(1) 0(2) 0(1) 0(1) 0(2) 0(2) 0(1)

EverittMem.Hwy USFS 1W

MarbleMtnWilderness

(BackMeadows,southpe

BoulderCreek

USFS ?U

MarbleMtnWildernessBear

Valleyrea5500ft

USFS ?U

MarbleMtnWildernessBig

Meadows^500ft

USFS ?U

MarbleMtnWilderness

LoweWrightLake7000ft

USFS ?U

MarbleMtnWilderness

PacificCrestTrail(.5miS

ParadiseLake)

USFS ?U

MarbleMtnWilderness

UpperKelsyCreek5600ft

USFS ?U

Montegue Private 0(1) 0(1)

Yreka Private 2W

WilloCreek,TrinityAlps,17

miNWeaverville

USFS ?U

TOTAL: 2 2 9 18 3 39 1 9 2 15 5 22 ? 1 1 13 2 15 32 1 2 10 98 2091203 0 0100000000000

CALIFORNIA

SiskiyouCounty

TrinityCounty

YEAR

(Q=Queen,W=worker,M=male,U=individualofunknowntype;numberinparenthesesindicatesnumberofdaysthesitewasvisitedthatyear

)

OREGON

DouglasCounty

JacksonCounty

JosephineCounty

Soilmodificationataportionofthesitein2004.

InundatedbyLakeApplegateaftercompletionofApplegateDaminFallof1980

Printed on 100 percent chlorine-free/100 percent post-consumer content recycled paper

Appendix 2: Dear Interested Party Letter

Reply To: 8185.0153

File Name: DIP Franklin bumble bee.doc

TS Number: 17-576

Dear (Interested Party),

The U.S. Fish and Wildlife Service (Service) is evaluating the status of Franklin’s

Bumble Bee (Bombus franklini) to determine the need for potential listing as an endangered or

threatened species under the Endangered Species Act of 1973, as amended (16 U.S.C 1531 et

seq.; Act). We initiated this process following our receipt of a petition dated June 23, 2010, from

the Xerces Society for Invertebrate Conservation, and Dr. Robbin Thorp (petitioners). The

petitioners requested listing of Franklin’s bumble bee as an endangered species and that critical

habitat be designated for the species. On August 16, 2010, we provided the petitioners with our

determination that an emergency listing was not warranted based on our assessment of the

immediacy of possible threats to Franklin’s bumble bee as presented in the petition. We also

informed the petitioners that at that time, we would not be able to further address the petition due

to requirements to complete a significant number of listing and critical habitat designations. In

September 2011, we published 90-day finding in the Federal Register (76 FR 56381), wherein

we determined that the petition presented substantial information indicating that the listing of the

Franklin’s bumble bee may be warranted. We also requested scientific and commercial data and

other information regarding this species at that time. With this letter, we are providing early

notification to our conservation partners that we are continuing with this status review process

(as initiated with the 90-day finding on September 13, 2011 (76 FR 56381).

Franklin’s bumble bee has been found in an area of about 190 miles north-south and 70

miles east-west in Douglas, Jackson and Josephine counties in southern Oregon and in Siskiyou

and Trinity counties in northern California, which is the most limited distribution known of any

bumble bee species in North America, and perhaps the world. Franklin’s bumble bee is a

eusocial bumble bee, and each colony goes through an annual cycle and only the queen lives

through the winter. The nesting biology of Franklin’s bumble bee is unknown, but like other

Bombus species, it is thought to nest underground in grassy areas, presumably in abandoned

rodent burrows. The flight season of Franklin’s bumble bee is from mid-May, when the queen

emerges from hibernation, to the end of September. Franklin’s bumble bee requires habitat with

a rich supply of floral resources that bloom continuously from spring to autumn. Bumble bees

are generalist foragers, meaning that they gather pollen and nectar from a wide variety of

flowering plants. Unlike honey bees, bumble bees do not produce honey for winter nutrition –

United States Department of the Interior

FISH AND WILDLIFE SERVICE

Oregon Fish and Wildlife Office

2600 SE 98

Avenue, Suite 100

Portland, Oregon 97266

Phone: (503) 231-6179 FAX: (503) 231-6195

rather, nutrition is derived from nectar, which provides carbohydrates, and from pollen provides

protein.

According to the petition, the primary threats to Franklin’s bumble bee in Oregon and

California, according to the petitioners, include exotic diseases introduced from commercial

bumble bees used for greenhouse pollination of tomatoes and field pollination of a variety of

crops; habitat loss due to destruction, degradation and conversion; pesticides and pollution; and

inadequacy of current rules, regulations and law. The petitioners also identified the following

additional threats: small population size, exotic plant species introduction, increased human use

of native habitat, climate change affecting alpine habitat, and alteration of wildfire severity and

intensity.

Our status review includes consideration of all of the best scientific and commercial data

available to us regarding Franklin’s bumble bee populations, and is not limited to the information

provided in the petition. Over the next several months, we will be gathering and analyzing

available information as part of our evaluation of the species’ status. We are required to use the

best scientific and commercial data available in the development of our finding to ensure our

analysis and finding is as accurate as possible. We are seeking your input to ensure we have the

best scientific data available to inform our finding.

We are particularly seeking information and data for Franklin’s bumble bee throughout

its range in Oregon and California regarding the following:

• Biology, range, and population trends, including:

o Habitat requirements for feeding, breeding, and sheltering;

o Genetics and taxonomy of the population;

o Historical and current range including distribution patterns, and presence or

absence of physical, physiological, or behavioral barriers to movement between

populations;

o Historical and current population levels, and current and projected trends; and

o Past and ongoing conservation measures for the species, its habitat, or both.

• The factors that are the basis for making a listing determination for a species under

section 4(a) of the Act, which are:

o The present or threatened destruction, modification, or curtailment of its habitat or

range;

o Overutilization for commercial, recreational, scientific, or educational purposes;

o Disease or predation;

o The inadequacy of existing regulatory mechanisms; or

o Other natural or manmade factors affecting its continued existence.

While we will accept new information throughout this process, we request that you

provide us with any pertinent information by August 3rd, 2017, to ensure we have adequate time

to consider it during development of our finding. If you have already provided us with any data

recently, thank you; there is no need to resubmit that information, as it will be fully considered in

our status review.

Information should be submitted to Jeff Everett of our Oregon Fish and Wildlife Office at

(503) 231-6952 ([email protected]). Please be aware that all data and information

submitted to us, including names and addresses, will become part of the decision record for this

package and will be available for public inspection.

Thank you for your interest in the conservation of Franklin’s bumble bee. If you would

like additional information about the listing process, please contact Rebecca Migala of our

Portland Regional Office at (503) 231-2011 ([email protected]). Additional

information on the listing process is available online at our website at

http://www.fws.gov/endangered/what-we-do/listing-overview.html.

Sincerely,

Paul Henson

State Supervisor

Appendix3:NeonicotinoidPesticideDatabyCounty,1995‐201

Imidacloprid Thiamethoxam Clothiandin Imidacloprid Thiamethoxam Clothiandin Imidacloprid Thiamethoxam Clothiandin Imidacloprid Thiamethoxam Clothiandin Imidacloprid Thiamethoxam Clothiandin Imidacloprid Thiamethoxam clothiandin

1995 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1995 n/a n/a n/a

1996 45.7 0 0 1.5 0 0 2.4 0 0 0 0 0 0 0 0 1996 3.75 0 0

1997 197.5 0 0 0.7 0 0 3 0 0 0 0 0 0 0 0 1997 0.16 0 0

1998 320.5 0 0 0.8 0 0 5.2 0 0 0 0 0 0 0 0 1998 0.239 0 0

1999 1.6 0 0 0.7 0 0 1.2 0 0 0 0 0 0 0 0 1999 n/a n/a n/a

2000 8.8 0 0 3.1 0 0 5.2 0 0 0 0 0 0 0 0 2000 3.05625 0 0

2001 92.8 73.8 0 3.6 0.1 0 7.4 1.2 0 0 0 0 0 0 0 2001 0.374 0 0

2002 18 99 0 6.6 0.2 0 11.3 1.7 0 0 0 0 0 0 0 2002 18.035 0 0

2003 69.3 16 0 0.9 0 0 2.5 0.3 0 14.9 0 0 0 0 0 2003 33.618 0 0

2004 14.5 0 0 4.5 0 0 9.1 0 0 4.6 0 0 0.1 0 0 2004 10.289 0 0

2005 8.7 5.4 0 2.6 0 0 6.2 0.1 0 24.4 0 0 0 0 0 2005 56.928 0 0

2006 2.5 76.1 0 0.7 0.3 0 2.6 1.2 0 13.2 0 0 0 0 0 2006 31.547 0 0

2007 11.4 12 0 2.8 0.1 0 7.9 0.2 0 16.7 2.5 0 0 0 0 2007 39.344 5.427 0

2008 1.6 0.3 0.2 1 0.2 0 2.3 0.1 0 11.7 0 0 0 0 0 2008 26.063 0 0

2009 3.5 54.5 0.2 1.3 0.3 0 4.1 1.1 0 37.1 0 0 0 0 0 2009 64.672 0.08 0

2010 3.1 1.2 0.3 1.1 0.4 0.1 2.3 0.2 0 0 0 0 0 0 0 2010 15.281 19.268 0

2011 9.7 0.3 1 3.3 0.1 0.4 8.2 0.1 0 0 4.8 0 0 0 0 2011 2.219 10.657 0

2012 4.7 11.4 1 2.4 0.1 0.5 5.7 3 0 132.3 3.4 0 0 0 0 2012 305.535 7.498 0

2013 22.4 0.9 3.4 10.6 0.3 1.8 25.2 0.2 0 487.6 14.1 0 0 0 0 2013 473.582 31.156 1.25

2014 152.8 30 3.5 78.8 0.6 1.8 155.6 7.9 0 276.7 12.4 0 0 0 0 2014 685.758 27.37 0

2015 436.8 0 0 37.9 0 0 19.8 0 0 64.1 0 0 0 0 0 2015 160.033 0 0

1995 0.7 0 0 1.8 0 0 0.9 0 0 0 0 0 0 0 0 1995 n/a n/a n/a

1996 2.2 0 0 47.3 0 0 3.9 0 0 0 0 0 0 0 0 1996 0 0 0

1997 1.7 0 0 199.9 0 0 4.6 0 0 0 0 0 0 0 0 1997 0 0 0

1998 1.4 0 0 322 0 0 6 0 0 0 0 0 0 0 0 1998 0 0 0

1999 0.9 0 0 2.2 0 0 1.5 0 0 0 0 0 0 0 0 1999 n/a n/a n/a

2000 2.8 0 0 316.1 0 0 8.7 0 0 0 0 0 0 0 0 2000 3.422 0 0

2001 3.6 0.2 0 92.8 73.9 0 7.4 1.3 0 0 0 0 0 0 0 2001 1.312 0 0

2002 6.7 0.2 0 18.6 99 0 11.5 1.7 0 0 0 0 0 0 0 2002 22.335 0 0

2003 1.4 0.1 0 70.8 16.2 0 3.4 0.4 0 14.9 0 0 0 0 0 2003 0 0 0

2004 4.7 0.3 0 15.3 116.4 0 9.5 1.9 0 4.6 0 0 0.1 0 0 2004 0.23 0 0

2005 2.9 0 0.2 40.4 5.4 0.9 7 0.1 0.9 24.4 0 0 0 0 0 2005 0.738 0 0

2006 0.8 0.3 0.2 2.8 76.1 52.4 2.8 1.2 0.8 13.2 0 0 0 0 0 2006 0.946 0 0

2007 3.6 0.1 1.5 57.6 12 352.7 9.4 0.2 5.2 16.7 2.5 0 0 0 0 2007 1.81 0 0

2008 1.1 0.4 0.3 18.3 49.3 63.4 2.7 0.8 1 11.7 0 0 0 0 0 2008 0.884 0 0

2009 1.4 0.3 0.3 32.5 54.8 50.6 4.7 1.1 0.8 37.1 0 0 0 0 0 2009 1.04 0 0

2010 2.8 0.6 0.1 16.4 45.5 0.3 6.6 1 0 0 0 0 0 0 0 2010 0 0 0

2011 3.7 0.1 0.4 65.1 13.8 1 10.7 0.3 0 0 4.8 0 0 0 0 2011 0.654 0 0

2012 2.8 0.4 0.5 64 68.5 1 8.6 4.1 0 132.3 3.4 0 0 0 0 2012 0.117 0 0

2013 11.2 0.8 1.8 110.7 97.2 9.6 27.6 2.6 0.1 487.6 14.1 0 0 0 0 2013 3.594 0.065 0

2014 79.1 0.9 1.8 215.4 81.4 3.5 157.8 8.8 0 276.7 12.4 0 0 0 0 2014 2.494 0 0

2015 38 0.3 0.1 436.9 47.5 18.8 80.2 0.9 0.3 64.1 0 0 0 0 0 2015 0.362 0 0.02

USGSDatafromhttps://water.usgs.gov/nawqa/pnsp/usage/maps/about.php.

ForallStatesexceptCalifornia,proprietaryfarmsurveypesticide‐usedataareaggregatedandreportedatthemulti‐countyCropReportingDistrictlevel

HarvestedcropacreagedatabycountyfromtheUSDepartmentofAgricultureCensusofAgricultureareusedtocalculatethemedianpesticide‐by‐cropuseratesforeachCR

EstimatesforCaliforniaareobtainedfromannualDepartmentofPesticideUseReports.MethodsforgeneratingcountylevelpesiticideuseestimatesaredescribedinThelinandStone,2013,andBakerandStone,2015

Thesedataareestimates‐pleaserefertotheUSGSwebsiteformoredetailedinformationonhowtheestimatesaregeneratedandimportantlimitationsondataus

CaliforniaPesticideInformationPortalcanbefoundathttp://calpip.cdpr.ca.go

CalPipdatabasedoesnothaveresultsfor1995and1999

2013rawCalpipdataincludesasingleapplicationof620.423poundsofimidaclopridon44acresofpotatosinsiskiyoucounty;notincludedhereassuspectederroneousdat

SiskiyouCounty,CACalPiPData

TrinityCounty,CACalPiPData

EPEST_LOWallcounties

EPEST_HIGHallcounties

TrinityCounty,CASiskiyouCounty,CADouglasCounty,ORJacksonCounty,ORJosephineCounty,OR

JosephineCounty,OR JacksonCounty,OR DouglasCounty,OR SiskiyouCounty,CA TrinityCounty,CA

Appendix 4: Expert Elicitation Questionnaire

Franklin’s bumble bee (Bombus franklini)- Questions from USFWS 10/27/2017

In our status assessment of B. franklini, we need to articulate the habitat requirements for a viable population of the species; we look at

viability in terms of what a reasonable naturalist would consider a stable, self-sustaining population. In order to get a better understanding of

the species’ population structure and habitat requirements, as well as the factors that might have influenced B. franklini populations, we have

the following questions:

1. What would the number of individual B. franklini recorded at a site indicate?

• Could you draw any conclusions on the number of colonies represented at the site?

(e.g. 3 bees= 1 colony, or 44 bees= more than 1 colony?)

• How big is the typical (most likely) colony foraging area (in km

) of B. franklini or other Bombus species that have similar foraging

behavior?

What is the largest?

Smallest?

• What is the probability (high, medium, or low) that Bombus colonies overlap in their foraging areas? (0-32% = low, 33-65% = medium, 66-

100% = high)

• What is the probability (high, medium, low) that at sites where multiple bees were counted over several visits (in all historical records

and surveys), that the same individual bee might have been counted twice? (0-32% = low, 33-65% = medium, 66-100% = high)

2. How many colonies would make up a viable population (as defined above in bold) of B. franklini or a similar species?

How large (in km

) would a habitat patch have to be to support a viable population?

3. In the past (pre- 1998), when people went out to collect native bumble bees including B. franklini, what was the probability (high, medium,

low) that a specimen of B. franklini was included in the day's collection? (0-32% = low, 33-65% = medium, 66-100% = high)

• Could people usually collect a Franklin's specimen if they knew where to find them or was it always a challenge to find them even at

sites where they previously occurred?

4. Can we infer from the historical data that a higher count of B. Franklini at a site was due to higher abundance of bees? Or… should we not

infer this because of the varying intensity of survey efforts (i.e. maybe they found more bees that year because they looked harder for the

bees)?

5. Can you suggest a species of Bombus that is similar to B. franklini that has been studied more (a species we can use as a surrogate for

information on population structure and habitat requirements)? If so, are there any caveats or considerations we should keep in mind

when using this species as a surrogate?

6. Would you consider any of the sites where B. franklini were found in the past (Table 1 below) extirpated or no longer viable?

Why or why not? How confident are you in your answer? (highly confident, confident, minimally confident)

7. In Table 1, please fill in any site-specific information you have on the following potential stressors at last known occurrence sites of B.

franklini. Do you think there are any other factors that may have led to the decline of B. franklini at any of these sites or elsewhere in the

historic range (Douglas, Jackson, and Josephine Counties, Oregon, and Siskiyou and Trinity Counties, California)?

Table 1: Potential stressors at known occurrence sites of Bombus franklini from 1997-2006 (occurrence site information taken from 2010 Petition

to List Franklin’s Bumble Bee (Thorp et al. 2010, p. 9 and Appendix 1)).

Pesticide Use

Grazing

Proximity to

commercially raised

bees

Wildfire

Changes in bloom time

of forage Vegetation

Invasive Species

Changes in habitat

(development or other)

Jackson County, Oregon

Sutherlin (3 miles

West of)

Ashland

Ashland Pond

Ashland (SOU_

Roca Canyon)

Buncom (1.5 miles

East of)

Gold Hill (3 miles

East of)

Significant excavation

and deposited soil in

2004- altered 50% of

bumble bee habitat

Grizzley Peak/ Shale

City Road

Jackson

campground

Kenney Meadows

Lost Creek

Reservoir

Medford- Roxy Ann

Peak

Mt. Ashland

Pesticide Use

Grazing

Proximity to

commercially raised

bees

Wildfire

Changes in bloom time

of forage Vegetation

Invasive Species

Changes in habitat

(development or other)

Phoenix (E of)

Ruch

Ruch (4 miles SSE

of)

Josephine County, Oregon

Selma (South of)

Siskiyou County, California

Hilt

8. In looking at the draft distribution map of known occurrences of B. franklini (below), are there areas in Douglas, Jackson, Josephine,

Siskiyou, and Trinity Counties in addition to these occurrence sites that might contain its known foraging plants (and therefore potential B.

franklini habitat): lupine (Lupinus spp.), California poppy (Eschscholzia californica), horsemint or nettle-leaf giant hyssop (Agastache

urticifolia) and mountain monardella (Monardella odoratissima)?