A Suckley cuckoo bumble bee.
Moderate
The population size of the Suckley's cuckoo bumble bee has experienced rapid declines in relative abundance in recent years. Recently, Suckley’s bumble bee was petitioned for listing under the Endangered Species Act. A 90-day finding by the U.S. Fish and Wildlife Service concluded that the western bumble bee petition presented substantial information that indicated that action may be warranted due to potential threats; therefore, a status review is currently being conducted to determine if the western bumble bee warrants listing.
Bumble bees have recently become the focus of conservation concern and efforts due to their precipitous population declines and prodigious capabilities as pollinators. In a recent status assessment, International Union of Conservation for Nature identified three Washington species as facing high or extremely high risk of extinction: western bumble bee and Morrison’s bumble bee were ranked Vulnerable, and Suckley's cuckoo bumble bee was ranked Critically Endangered.
Description and Range
Physical description
Suckley's cuckoo bumble bee is classified within the Psithyrus subgenus. This subgenus differs morphologically from other Bombus subgenera because its members to do have corbicula or pollen-carrying baskets on their hind legs. See the Pacific Northwest Bumble Bee Atlas for a detailed description of this bumble bee species. Williams, et al. (2014) describes 5 morphological types of females (no workers) and 4 morphological types for males across the species range.
Ecology and life history
Suckley’s cuckoo bumble bee is a cuckoo bumble bee or obligate social parasite of other Bombus species. Suckley’s cuckoo bumble bee has been recorded as a parasite to colonies of Bombus occidentalis, Bombus rufocinctus and Bombus appositus.
All individual female Suckley’s cuckoo bumble bees are able to reproduce but cannot provision their own offspring because they are unable to produce a worker caste, enough wax for nest construction, and have no pollen-collecting basket on their hind legs. Cuckoo bumble bees enter developing and established nests of other bumble bees, kill or subdue the host queen, lay her own eggs and control the workers to continue collecting pollen and nectar to provision (feed) her offspring. Once developed, Suckley’s adults leave the nest to mate; mated females feed on nectar and pollen prior to overwintering and males die after mating.
In general, bumble bees depend on habitats with rich floral resources throughout the nesting season, and many species select specific suites of plants for obtaining nectar and pollen. They also select flowers based on their structure and the bee’s tongue length. For example, the short to medium length-tongued Suckley’s cuckoo bumble bee uses shallow to medium-depth flowers.
Bumble bees require above and below-ground micro-sites for overwintering and nesting, including logs, stumps, and abandoned rodent and ground-nesting bird nests.
Bumble bees are adaptable; they do not require native vegetation. However, intensive agricultural development has been shown to result in regional bumble bee declines. Although habitat loss and insecticide use have played a role in bumble bee declines, their rapid and widespread declines even from apparently high quality habitats support the current prevailing hypothesis that pathogens introduced into the wild from commercial bumble bee facilities are the main factor in declines.
Bumble bees are key generalist pollinators of native plants and agricultural crops. Through their foraging and collection of nectar and pollen they physically transfer the latter between plants, allowing them to reproduce.
The bumble bees' unique behavior of “buzz pollination”, in which they grab onto and strongly shake an entire flower by vibrating their powerful wing muscles, results in large amounts of pollen being released and produces a more complete fruit set than other pollinators, including honey bees.
Geographic range
Suckley's cuckoo bumble bee species historically occurred in healthy populations across large geographic areas; it was found in western Canada and the United States: southwestern Manitoba southwest to western South Dakota south to southern Colorado west to northern California north to the Yukon and Northwest Territories south to central British Columbia; a few populations have also been documented in eastern Canada. This cuckoo bumble bee historically was found throughout Washington.
Recent surveys reveal significant declines in their numbers, distribution, and ranges. Range-wide surveys in Washington detected this species in only six localities, including one near far northeastern part of the state.
For a maps of the geographic range and conservation status of Suckley's cuckoo bumble bee and other information, check out NatureServe Explorer and the International Union for Conservation of Nature Red List.
Climate vulnerability
Sensitivity to climate change
Moderate
There is no information regarding the sensitivity of this species to climate change. In general, bumblebees are likely sensitive to climate-driven changes in nesting, foraging, and overwintering habitat, but detailed information is currently lacking. Shifts in temperature, precipitation, and snowpack may affect bumblebee distribution and life history, potentially forcing them into unfavorable habitats, to emerge at non-optimal times (i.e., mismatch with vegetation), and/or affecting energy demands during overwintering periods. These climate-driven changes may also affect habitat quality and availability. One of the primary concerns for bumblebee species is a shift in the abundance, distribution, and/or phenological synchrony of key forage flowering vegetation, as pollen and nectar availability influences reproduction and overwintering success of queens.
Exposure to climate change
Moderate
- Increased temperatures
- Changes in precipitation and/or soil moisture
How to
Check out Habitat At Home to learn ways to attract pollinators in your own backyard, such as planting pesticide-free and native plants for butterflies and bees on your landscape or in a container garden; and see how to a craft a bee hotel! Habitat at Home, formerly known as the Backyard Wildlife Sanctuary Program, is the Washington Department of Fish and Wildlife's effort to encourage Washingtonians to connect with nature where they live.
Conservation
Conservation Threats and Actions Needed
- Agricultural and aquaculture side effects
- Threat: Importation of bumble bees for use in pollination of commercial crops introduces pathogens into the wild.
- Action Needed: Review of federal/state policies that allow translocation and establishment of commercially-reared bumble bees in North America.
- Resource information collection needs
- Threat: Lack of data on current status and distribution.
- Action Needed: Determine distribution and population status.
The habitats of this species must also be protected from insecticides.
See the Climate vulnerability section for information about the threats posed by climate change to this species. Climate vulnerability (PDF) is a way to assess the degree to which a habitat or species is susceptible to, and unable to cope with adverse impacts of climate change.
Our Conservation Efforts
The Western States Bumble Bee Atlas strives for conservation across four western states
The Washington Department of Fish and Wildlife is taking part in an initiative that unites Oregon, Washington, Idaho, and California in a conservation effort dedicated to understanding and protecting bumble bees. The Western States Bumble Bee Atlas will establish a regionwide network to gather data to provide a better understanding of bumble bee distributions and habitat needs. This project builds on work done since 2018 by the Pacific Northwest Bumble Bee Atlas, a collaboration between state agencies and conservation organizations in Oregon, Washington, and Idaho. Fueled by volunteer community scientists, the atlas gathers data throughout the three-state area that helps shape conservation work. The project is funded by the U.S. Fish and Wildlife Service’s Wildlife and Sportfish Restoration program through a competitive State Wildlife Grant, the U.S. Forest Service, the Bureau of Land Management, and the Oregon Conservation and Recreation Fund. Now, California is joining this effort, extending the geographic area covered to almost 15% of the contiguous United States. Nearly 60% of North America’s bumble bee species are known to occur in this region, underscoring the importance of this initiative.
Resources
References
Goulson, D. (2010). Bumblebees behaviour, ecology, and conservation (2nd. Ed.). Oxford New York : Oxford University Press.
Hatfield, R., S. Colla, S. Jepsen, L. Richardson, and R. Thorp. 2015. IUCN assessments for North American Bombus spp. for the North American IUCN bumble bee specialist group. The Xerces Society for Invertebrate Conservation. Portland, OR. https://www.iucnredlist.org/species/44937666/69004519
Hatfield, R., L. Svancara, L.L. Richardson, J. Sauder, and A. Potter. 2021. The Pacific Northwest Bumble Bee Atlas: Summary and Species Accounts—A collaboration between the Xerces Society, Idaho Department of Fish and Game, and Washington Department of Fish and Wildlife, pp. 73. https://xerces.org/publications/guidelines/pnw-bumble-bees
USFWS. 2021. Federal Register. Endangered and Threatened Wildlife and Plants; 90-Day Finding for Three Species [Suckley’s cuckoo bumble bee]. 86 FR 25833. https://www.federalregister.gov/documents/2021/05/11/2021-09707/endangered-and-threatened-wildlife-and-plants-90-day-findings-for-three-species#p-38
Williams, P.H., R.W. Thorp, L.L. Richardson, and S.R. Colla. 2014. Bumble Bees of North America: An Identification Guide. Princeton: Princeton University Press.