The western bumble bee was historically one of the most common bumble bees across the western U.S. and Canada. However, our research and others found it has declined substantially across its range and the U.S. Fish and Wildlife Service is considering it for listing under the Endangered Species Act. Bureau of Land Management, National Park Service, and other land managers need information to inform decisions about multiple bumble bee species of conservation concern. Using co-produced science, we collect and integrate data to directly answer our partner’s pressing questions.
In addition, we are developing methods to efficiently and robustly research and monitor pollinators including sampling pollinator genetic material deposited on flowers (eDNA), statistical approaches incorporating detection probability, and testing photographic identification approaches for bumble bees. We work with partners including the Bureau of Land Management Montana-Dakotas and Glacier National Park. Together, these projects inform where and which conservation actions could most benefit pollinators.
Background & Importance
Very little is known about most pollinators, even bumble bees, which are charismatic in the insect world. North America’s ~4500 native bees, including the western bumble bee, are among the most effective pollinators and most of the fruits and vegetables in our grocery stores are pollinated by them. Bumble bees also pollinate many wildflowers and wildlife foods, including huckleberries, an important food for grizzly bears, black bears, birds, and small mammals. Thus, they have an important role in supporting wildlife species as well as agricultural crops. Threats facing bumble bees include habitat loss, pesticides, disease, invasive insects, and climate change—which influences the timing of when the flowers they depend on are available.
There are at least 45 species of bumble bees in North America. While we know much of the basics of their life histories, the details that can best inform conservation, such as the habitat needed for nesting and overwintering, the interactions with other bumble bee species, and how to mitigate threats to their populations are still urgently needed.
Projects
1) Informing western and McKay’s bumblebees (Bombus occidentalis and Bombus mckayi) Species Status Assessment (SSA)
The USFWS SSA provides a summary of what is known about a species as a foundation for listing decisions. We worked extensively with a wide array of experts to prioritize information needs with the goal of completing the highest priority research to inform the SSA. We conducted initial analyses to evaluate trends in occupancy and developed a sample design to address spatial gaps and guide consistent data collection. Using updated data from the most recent sampling efforts, we next assessed effects of multiple stressors on the western bumble bee in the continental U.S., refining occupancy analyses to assess potential mechanisms of declines including climate, landcover, and pesticides. This provides information on the past and current distribution. We then projected future distributions based on changes in climate, landcover, and other conditions. As some of the first applications of occupancy models to pollinators, or even insects generally, we identified methods to accommodate their complex life history in these statistical approaches while accounting for surveys that do not detect the bumble bee when it is present. We also developed maps and predictions for the number of surveys needed to detect this species of concern if it is present.
The western bumble bee petition for listing included 2 subspecies, B. occidentalis occidentalis and B. occidentalis mckayi, which have since been separated into 2 species (B. occidentalis and B. mckayi). We are completing similar work for McKay’s bumble bee, distributed in western Canada and Alaska.
2) Research with the Bureau of Land Management (BLM) land in Montana, North Dakota, and South Dakota
Surveys on BLM land were designed for multiple objectives, providing a testing ground for many methodological questions and information for on-the-ground management. First, as lands with limited information on pollinators, surveys filled important information gaps for the distribution of western and other bumble bee species. Second, we collected bumble bees using both photographic and specimen methods for identification to quantify success rates and identify best practices and limitations of nonlethal photographic methods. Third, we are assessing pollinator networks, linking bee species with the flowers they use for food. Fourth, we are assessing how management and habitat characteristics influence the distribution of bumble bee species by integrating data collected through BLM’s AIM program. Finally, we are evaluating how to collect data most efficiently in these remote areas, including cost-effective field protocols for eDNA data collection.
3) Using pollinator environmental (eDNA) to assess ecological resilience of restored grasslands
We are working with scientists across 6 USGS Science Centers, multiple universities, BLM, U.S. Fish and Wildlife Service, National Park Service, and other partners to develop robust and efficient approaches to identify pollinators based on the DNA they leave behind when they visit flowers. Using both lab and field-based experiments, we aim to broaden our understanding of connections among pollinator communities and flowers in grasslands, one of the most imperiled ecosystems in the U.S. to inform the National Seed Strategy and restoration practices.
4) Glacier National Park bumble bees
We surveyed for bumble bees and other pollinators in grasslands and adjacent landcover as part of a multi-species project to understand baseline conditions prior to the Blackfeet Nation’s planned reintroduction of bison (Iinii Initiative). This builds on work identifying pollinators of huckleberries. As an area where northern, western, and eastern species converge, with 24-28 bumble bee species, including the western bumble bee, this florally diverse ecosystem provides a benchmark for relatively intact interactions. In addition to providing information for western bumble bee assessments, these data will inform assessments of effects of hydrologic and landcover change on bees, in a multi-park project ‘From Water to Wildlife.’
Methods
Different bee species and other pollinators are best surveyed with specific methods targeted towards their individual behaviors. For bumble bees, timed surveys with nets are among the most effective methods for catching and identifying different species. Although different bumble bee species may look similar and may even be found in similar habitats, they likely vary in their susceptibility to threats. Sampling a 100m x 100m (328’ x 328’) plot for bumble bees for 45 minutes can result in the detection of anywhere from 0 to over 100 bumble bees. Habitat data, including the plants that are flowering, presence of potential nesting habitat, and the types of disturbance in the area can be fed into an occupancy model, which is used to understand the detectability of each bumble bee species and the probability that a species of bumble bee is present at a site with a particular combination of environmental conditions. These and other methods are used to compare bumble bee species distributions, evaluate their relationships to flowering resources, and more. For regional modeling efforts, including recent assessment of the western bumble bee, community science data, such as photos contributed to iNaturalist and Bumble Bee Watch, play a valuable role in model validation and identification of existing populations of bee species.
Story detailing bees and citizen scientists: https://storymaps.arcgis.com/stories/c5e591a19eb24d28af483ede7b174434
- Overview
The western bumble bee was historically one of the most common bumble bees across the western U.S. and Canada. However, our research and others found it has declined substantially across its range and the U.S. Fish and Wildlife Service is considering it for listing under the Endangered Species Act. Bureau of Land Management, National Park Service, and other land managers need information to inform decisions about multiple bumble bee species of conservation concern. Using co-produced science, we collect and integrate data to directly answer our partner’s pressing questions.
In addition, we are developing methods to efficiently and robustly research and monitor pollinators including sampling pollinator genetic material deposited on flowers (eDNA), statistical approaches incorporating detection probability, and testing photographic identification approaches for bumble bees. We work with partners including the Bureau of Land Management Montana-Dakotas and Glacier National Park. Together, these projects inform where and which conservation actions could most benefit pollinators.
Sources/Usage: Public Domain.The western bumble bee has almost entirely disappeared from its West Coast range in part due to a 1990s epidemic. Although multiple populations persist, drought, warming, and pesticides contribute to a reduced distribution that we project will continue to decline under most future scenarios. Note that there are several color variations of this species. This one is representative of those found in the Rockies. (Credit: USGSBIML Team, Public domain.) Background & Importance
Very little is known about most pollinators, even bumble bees, which are charismatic in the insect world. North America’s ~4500 native bees, including the western bumble bee, are among the most effective pollinators and most of the fruits and vegetables in our grocery stores are pollinated by them. Bumble bees also pollinate many wildflowers and wildlife foods, including huckleberries, an important food for grizzly bears, black bears, birds, and small mammals. Thus, they have an important role in supporting wildlife species as well as agricultural crops. Threats facing bumble bees include habitat loss, pesticides, disease, invasive insects, and climate change—which influences the timing of when the flowers they depend on are available.
There are at least 45 species of bumble bees in North America. While we know much of the basics of their life histories, the details that can best inform conservation, such as the habitat needed for nesting and overwintering, the interactions with other bumble bee species, and how to mitigate threats to their populations are still urgently needed.
Projects
1) Informing western and McKay’s bumblebees (Bombus occidentalis and Bombus mckayi) Species Status Assessment (SSA)
The USFWS SSA provides a summary of what is known about a species as a foundation for listing decisions. We worked extensively with a wide array of experts to prioritize information needs with the goal of completing the highest priority research to inform the SSA. We conducted initial analyses to evaluate trends in occupancy and developed a sample design to address spatial gaps and guide consistent data collection. Using updated data from the most recent sampling efforts, we next assessed effects of multiple stressors on the western bumble bee in the continental U.S., refining occupancy analyses to assess potential mechanisms of declines including climate, landcover, and pesticides. This provides information on the past and current distribution. We then projected future distributions based on changes in climate, landcover, and other conditions. As some of the first applications of occupancy models to pollinators, or even insects generally, we identified methods to accommodate their complex life history in these statistical approaches while accounting for surveys that do not detect the bumble bee when it is present. We also developed maps and predictions for the number of surveys needed to detect this species of concern if it is present.
The western bumble bee petition for listing included 2 subspecies, B. occidentalis occidentalis and B. occidentalis mckayi, which have since been separated into 2 species (B. occidentalis and B. mckayi). We are completing similar work for McKay’s bumble bee, distributed in western Canada and Alaska.
2) Research with the Bureau of Land Management (BLM) land in Montana, North Dakota, and South Dakota
Surveys on BLM land were designed for multiple objectives, providing a testing ground for many methodological questions and information for on-the-ground management. First, as lands with limited information on pollinators, surveys filled important information gaps for the distribution of western and other bumble bee species. Second, we collected bumble bees using both photographic and specimen methods for identification to quantify success rates and identify best practices and limitations of nonlethal photographic methods. Third, we are assessing pollinator networks, linking bee species with the flowers they use for food. Fourth, we are assessing how management and habitat characteristics influence the distribution of bumble bee species by integrating data collected through BLM’s AIM program. Finally, we are evaluating how to collect data most efficiently in these remote areas, including cost-effective field protocols for eDNA data collection.
3) Using pollinator environmental (eDNA) to assess ecological resilience of restored grasslands
We are working with scientists across 6 USGS Science Centers, multiple universities, BLM, U.S. Fish and Wildlife Service, National Park Service, and other partners to develop robust and efficient approaches to identify pollinators based on the DNA they leave behind when they visit flowers. Using both lab and field-based experiments, we aim to broaden our understanding of connections among pollinator communities and flowers in grasslands, one of the most imperiled ecosystems in the U.S. to inform the National Seed Strategy and restoration practices.
4) Glacier National Park bumble bees
We surveyed for bumble bees and other pollinators in grasslands and adjacent landcover as part of a multi-species project to understand baseline conditions prior to the Blackfeet Nation’s planned reintroduction of bison (Iinii Initiative). This builds on work identifying pollinators of huckleberries. As an area where northern, western, and eastern species converge, with 24-28 bumble bee species, including the western bumble bee, this florally diverse ecosystem provides a benchmark for relatively intact interactions. In addition to providing information for western bumble bee assessments, these data will inform assessments of effects of hydrologic and landcover change on bees, in a multi-park project ‘From Water to Wildlife.’
Methods
Sources/Usage: Public Domain.USGS scientist Tabitha Graves collects western bumble bee samples in eastern Montana. Different bee species and other pollinators are best surveyed with specific methods targeted towards their individual behaviors. For bumble bees, timed surveys with nets are among the most effective methods for catching and identifying different species. Although different bumble bee species may look similar and may even be found in similar habitats, they likely vary in their susceptibility to threats. Sampling a 100m x 100m (328’ x 328’) plot for bumble bees for 45 minutes can result in the detection of anywhere from 0 to over 100 bumble bees. Habitat data, including the plants that are flowering, presence of potential nesting habitat, and the types of disturbance in the area can be fed into an occupancy model, which is used to understand the detectability of each bumble bee species and the probability that a species of bumble bee is present at a site with a particular combination of environmental conditions. These and other methods are used to compare bumble bee species distributions, evaluate their relationships to flowering resources, and more. For regional modeling efforts, including recent assessment of the western bumble bee, community science data, such as photos contributed to iNaturalist and Bumble Bee Watch, play a valuable role in model validation and identification of existing populations of bee species.
Story detailing bees and citizen scientists: https://storymaps.arcgis.com/stories/c5e591a19eb24d28af483ede7b174434
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