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Morrison Bumble Bee ESA Petition FAQ

Morrison bumble bee (Bombus morrisoni) was proposed for listing under the Endangered Species Act in 2023 through a petition submitted by the Xerces Society.


What are Morrison bumble bees, and where are they found?

Morrison bumble bee (Bombus morrisoni) is one of approximately 50 bumble bee species that occur in the US and Canada.  Morrison bumble bees, like other social bumble bees, live in colonies consisting of a queen, her offspring, the workers, and near the end of the season, the reproductive members of the colony, the males and new queens. Morrison bumble bees collect pollen and nectar from many different flowering plants, and can be found in a variety of habitats including grasslands, sagebrush steppe, and woodland edges. Some populations can be found in urban environments including parks and residential yards. This species, like other bumble bees, is an important pollinator. The species’ range in the United States includes Arizona, California, Colorado, Idaho, Nebraska, Nevada, New Mexico, Oregon, South Dakota, Texas, Utah, Washington, and Wyoming. The species does not occur in the rest of the United States.

Why do Morrison bumble bees need Endangered Species Act (ESA) protection?

In the 1990s, Morrison bumble bees became much less common in bumble bee records, relative to other bumble bee species. Recent analysis shows that in the last decade, Morrison bumble bees have declined in relative abundance by 74%, and persist in 66% less area than they did historically. These analyses used a database of over 700,000 bumble bee records assembled from academic, research, private collections, and community scientists, using specimen and observation occurrences (Richardson 2022). Relative abundance of Morrison bumble bees is considerably lower than it was historically in every place across its range where it has been systematically monitored, including in California, Idaho, Oregon, and Washington. Additionally, the species has not been recently detected in approximately 14% of its historic range. These findings are consistent with a 2015 assessment of the extinction risk of the species, which found that Morrison bumble bees have declined in range size, persistence and relative abundance. Without ESA protection, this species may continue to decline to the point of extinction, which could lead to wide ranging ecological consequences.

Why are Morrison bumble bees threatened with extinction?

While it may be hard to pin the decline of Morrison bumble bees on one particular threat across space and time, extinction risk analyses and monitoring efforts show that this species is much less common than it was historically. The decline of Morrison bumble bees across their range is likely due to multiple ongoing and interacting threats. These include habitat degradation, habitat loss to agriculture and development, exposure to pesticides and pathogens, competition with commercial bees, and the effects of climate change. Many populations occur on rangelands, which have been degraded by overgrazing and drought, and thus may lack the pollen and nectar resources required by Morrison bumble bees for the entirety of their life cycle. Additionally, populations on some rangelands may be threatened by large-scale insecticide treatments that are applied to control particular rangeland pests. Human populations in many western states are expected to grow by 15% or more between 2020 and 2040, resulting in development that will continue to eliminate the habitats used by Morrison bumble bees. Morrison bumble bee populations that occur in agricultural lands may be killed by insecticides meant for pests. The species is also vulnerable to pathogens that spread from commercial bumble bees and honey bees used in crop pollination. Finally, populations across western North America are threatened by the effects of climate change, including increased temperatures and decreased precipitation, which can affect the quality and quantity of pollen and nectar resource plants on which the species depends.

How will protecting Morrison bumble bee as an endangered species under the Endangered Species Act help this bee?

Listing Morrison bumble bees as endangered under the Endangered Species Act will allow the U.S. Fish and Wildlife Service to create a recovery plan for the species and set guideposts for success. Listing would also include a variety of automatic prohibitions, including prohibitions on 'take,' which means any attempt to "harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect" the species. During the decision to list a species, the agency can also designate critical habitat to protect areas that are essential to Morrison bumble bees.

How might ranchers be affected if Morrison bumble bees are protected through the ESA?

Many observations of Morrison bumble bees come from rangelands in the western U.S., including property managed by the Bureau of Land Management (BLM) and U.S. Forest Service (USFS). If Morrison bumble bees are protected as an endangered species, a take prohibition would be put in place. Ranchers can be protected from liability associated with incidental take of an endangered species by developing a Habitat Conservation Plan to minimize and mitigate impacts. On private or non-federal land, the Endangered Species Act also allows for voluntary agreements for property owners whose actions contribute to the recovery of species listed as endangered, which in turn protect them from liability associated with a take prohibition that may be put in place. Ranchers using conservation practices approved by the Natural Resources Conservation Service can also enter into a Working Lands for Wildlife conservation agreement to allow for incidental take of animals during the implementation of these practices.

On federally managed land, the U.S. Fish and Wildlife Service would consult with federal agencies (such as the BLM and USFS) when they take actions that may harm Morrison bumble bees or degrade their habitat. For example, if a formal assessment determines that grazing is adversely affecting Morrison bumble bees on federally managed grazing land, voluntary agreements between ranchers with public grazing leases and the U.S. Fish and Wildlife Service may allow ranchers to receive Safe Harbor Agreements.

How would ESA protection for Morrison bumble bees affect croplands?

Many of the species’ currently preferred habitats are not near croplands nor row crops. In places like central and eastern Washington and southern Idaho, where the bumble bee is found on or near agricultural fields, listing Morrison bumble bee as an endangered species would prohibit take. However, the Endangered Species Act allows for voluntary agreements involving private or other non-Federal property owners whose actions contribute to the recovery of species listed as endangered. In exchange for actions that contribute to the recovery of listed species, participating property owners receive formal assurances, called a Safe Harbor Agreement, which grants permission for incidental take of the species and prevents the U.S. Fish and Wildlife Service from requiring additional management activities. For example, land owners could manage out-of-production land near croplands to benefit Morrison bumble bees by increasing the amount of forage for the species, without being subject to additional regulatory restrictions because of their efforts.

How might researchers and community scientists be affected by a listing of Morrison bumble bees?

Projects on private lands involving a federal nexus (e.g. federal permits or assistance) will require FWS review to ensure activities are not negatively impacting the species. Projects that may cause take and are assisting in the recovery of the species will require a federal recovery permit. For any research activities that will require a permit once this species is listed, the Xerces Society continues to recommend that the U.S. Fish and Wildlife Service streamline the permitting process in order to facilitate study by professional researchers, community scientists, and other amateur entomologists, recognizing the critically important role of these activities in species conservation.

What is the process for this petition?

While some stages of the petition process occur more quickly than others, the entire process may take years. 

  1. 90-day finding: From the date that the petition was filed, the U.S. Fish and Wildlife Service has 90 days, to the extent that it is possible, to make an initial finding on whether our petition has substantial information indicating that listing Morrison bumble bees may be warranted. 
  2. 12-month review: If a positive 90-day finding is issued (the FWS finds that listing may be warranted), Service biologists will conduct a Species Status Assessment (SSA). The SSA is a peer-reviewed status review of the best available science to assess the species’ ecology, abundance, population trends, and threats in order to evaluate the species’ current status and extinction risk. A review of conservation efforts is also completed. Following this, the Service will issue a final positive or negative finding on whether listing Morrison bumble bees as threatened or endangered is warranted. However, given the substantial workload of the U.S. Fish and Wildlife Service, 12-month findings can take longer than 12 months; the Service publishes a National Listing Workplan with a specific timeline of when 12-month findings will be completed for species that have been petitioned and have received positive 90-day findings. 
  3. Public comment period: If a 12-month finding determines that listing is warranted, the Service will solicit public comment and may hold public hearings. 
  4. Final ruling: Finally, after considering public input and any new additional information, the Service issues a final ruling, typically within a year (but sometimes longer). Sometimes the species is listed immediately, but other times the species’ listing is precluded by higher priorities. If listing is precluded by higher priorities, the species becomes a Candidate for protection, as the monarch butterfly is currently (November 2023).

What does the Xerces Society hope to accomplish by filing this petition for Morrison bumble bees?

The Xerces Society is a science-based, nonprofit organization dedicated to the conservation of invertebrates and their habitats. We are named after the now-extinct Xerces blue butterfly. Recent studies have found more than a quarter of North American bumble bees are at risk of extinction. These species are not only charismatic and beautiful, but they are also valuable pollinators in both agricultural and wildland settings. While some species of insects, such as the monarch butterfly, have received much-due attention for their decline, data from long-term insect monitoring programs have shown that many other insects are in a similar state of danger, including Morrison bumble bees. The Xerces Society and hundreds of volunteers are dedicated to continuing to monitor this and other species, and using the best available scientific evidence to protect and advocate for imperiled species of bumble bees. 

Listing Morrison bumble bees as an endangered species is a critically important step to prevent the species from declining to the point of imminent extinction. The Endangered Species Act is the nation’s most effective law for protecting animals and plants in danger of extinction, and it has prevented 99% of listed species from going extinct. An ESA listing will incentivise research and funding for the management of existing populations and their habitat, helping to reverse the ongoing declines this species is currently experiencing. Without this type of intervention, the species will likely continue to decline, possibly to the point of extinction.

How can I help Morrison bumble bees?

Morrison bumble bees will benefit from actions that create and conserve high quality habitat across the bee’s range. Maintaining and enhancing existing natural areas including grasslands, meadows, and sagebrush steppe to provide abundant and diverse flowering plants, is the easiest and most important step to conserve existing Morrison bumble bee populations. Importantly, the lands surrounding these flowering habitats are also important for protecting nesting and overwintering habitat - just planting flowers is likely not the only answer.

There are several critical components to quality habitat for this species. First is abundant nectar and pollen sources from spring to fall. Flowering resources are especially important in early spring for colony initiation, and late summer, when landscapes tend to dry out and resources are more limited. Some native plants that may be particularly important in the diet of Morrison bumble bees include native milkvetches (Astragalus), beebalms (Monarda and Monardella), thistles (Cirsium), lupines (Lupinus), rabbitbrush (Chrysothamnus and Ericameria), sunflowers (Helianthus), and milkweeds (Asclepias). Second, Morrison bumble bees need access to nesting and overwintering sites. Nesting and overwintering sites require stable nesting and overwintering habitat features, with some structural complexity. Habitat elements including downed wood, rock piles, moss, leaf litter (including pine needles), exposed loose soils and native bunch grasses can contribute to quality nesting and overwintering habitat. Third, Morrison bumble bees need protection from exposure to pesticides. Alternative management strategies should be sought to avoid the use of pesticides where the species occurs. Restoration practices, including those targeting the removal of non-native plants, should use a phased approach to avoid altering all habitat at once — including the removal of floral resources, and a revegetation plan should be in place to replace the pollen and nectar resources the non-native plants provided. Additionally, managed honey bees can compete with Morrison bumble bees for resources. As such, apiaries should not be placed within two miles of any area where Morrison bumble bees occur. 

More data is needed to understand the biology of Morrison bumble bees. You can contribute your observations of this species to Bumble Bee Watch, or participate in survey efforts as part of a Bumble Bee Atlas. You can find native pollinator-friendly native plant lists for your area on the Xerces Society website, as well as general guidelines for bumble bee conservation. There are additional resources available on providing bee habitat on farmland.


Database reference used in analysis for petition:

Richardson, L. L. 2022. Bumble bees of North America occurrence records database. Data accessed 07-15-2022.