Like many other species that once inhabited the prairies of the American Midwest, the rusty patched bumble bee (Bombus affinis), whose range historically extended from the Midwest to the Northeast, is in decline. Wild populations have dropped almost 90 percent in the last 20 years for this species now listed as Endangered in the US under the Endangered Species Act and as Critically Endangered on the IUCN Red List of Threatened Species. With a US Fish and Wildlife Service (USFWS) recovery plan in development for this species, experts from the US and Canada gathered in February at the Minnesota Zoo for a CPSG-facilitated meeting to evaluate potential ex situ strategies that could contribute to viable wild rusty patched bumble bee populations in the future. Many ex situ management options were considered and evaluated, based on the decision process outlined in the IUCN SSC Guidelines for the Use of Ex Situ Management for Species Conservation.

The rusty patched bumble bee faces threats from habitat loss, intensive farming, pesticides, disease, and climate change. Like other bumble bee species, a colony of rusty patched bumble bees dies off in the fall, except for new queens that fly to different locations to form their own colonies. The queen hibernates over winter, hidden under leaves and duff, to survive. In the spring, she emerges to start a new colony, laying eggs that become new workers, males and new queens for the next year. This unusual life cycle that depends on the survival of queens over winter makes bumblebee populations particularly vulnerable.

To help the bees combat the threats they face, the USFWS recommends conducting population surveys, creating and enhancing habitat, reducing stressors, and conducting research on key uncertainties. This last recommendation is crucial for the success of potential ex situ strategies for bee conservation. Not much is known, for instance, about bee food preferences or how they survive over winter and during other stages of their life cycle. Without this knowledge, attempts to boost wild populations by raising bees for release, or to establish a captive breeding insurance population for the species, may not be successful.

Experts are committed not only to closing knowledge gaps about the needs of rusty patched bumble bees but to taking action to prevent further decline of the species. At the meeting in February, the group united around recommendations for ex situ conservation actions, which will be available in a forthcoming report that will serve as a guide to action for partners working to save the rusty patched bumble bee.

This important workshop was organized in collaboration with, and supported by, USFWS, Ohio State University, and the Minnesota Zoo. Nearly 30 participants from over a dozen organizations contributed to making this a successful meeting that built unity around actions to improve the future for the rusty patched bumble bee.