Western Bumblebee and Native Pollinator Research

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The western bumblebee occurs across western U.S. and Canada, and was one of the most common bumblebees in this region. However, our research and others suggests it has been declining, and the U.S. Fish and Wildlife Service are considering it for listing under the Endangered Species Act. Data are needed to improve our understanding of the resilience, redundancy, and representation of the western bumblebee, and the threats influencing the species’ status. We have evaluated information gaps and developed a sample design and protocol to address spatial gaps and guide consistent data collection over the next two years. We welcome and invite participation in addressing information needs by conducting western bumblebee occupancy surveys and by incorporating new data into the next part of the research, which will compare the effects of multiple stressors. If you are part of a state or federal agency, or research institution, and are interested in joining our efforts, please contact Dr. Tabitha Graves at tgraves@usgs.gov

The second project is to survey pollinators on Bureau of Land Management lands in Montana and South Dakota to expand the limited information we have on pollinators. 

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This bumblebee species has almost entirely disappeared from its West Coast range due to a recent epidemic sweeping through some bumblebee populations. However, the Rocky Mountain populations still persist and there is hope that the West Coast population will also recover and resume its place as one of the most common bumblebee species in the West. 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 pollinator species, even bumblebees, which are charismatic in the insect world.  Native bees, including the western bumblebee, are among the most effective pollinators and a large percentage of the fruits and vegetables in our grocery stores are pollinated by them.  Bumblebees also pollinate many wildlife foods, including huckleberries, which is an important food for grizzly bears and black bears.  Thus, they have an important role in supporting wildlife species as well as agriculture. Threats facing bumblebees 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 bumblebees in North America.  While we know the basics of their life histories, the details that can best inform conservation, such as the habitat needed for nesting, the interactions with other bumblebee species, and how to mitigate threats to their populations are still urgently needed.  



Different bee species and other pollinators are best surveyed with specific methods targeted towards their behaviors.  For bumblebees, timed surveys with nets are among the most effective methods for catching and identifying different species. Although different bumblebee 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 bumblebees for 45 minutes can result in the detection of anywhere from 0 to approximately 100 bumblebees. Habitat data, including the plants that are flowering, presence of potential nesting habitat, and the types of disturbance in the area is then fed into an occupancy model, which is used to understand the detectability of each bumblebee species and the probability that a species of bumblebee is present in a particular combination of environmental conditions.  These and other methods are used to compare bumble bee species distributions, evaluate their relationship to flowering resources, and more. 


Story detailing bees and citizen scientists: https://storymaps.arcgis.com/stories/c5e591a19eb24d28af483ede7b174434