Monitoring and Habitat Assessment of Declining Bumble Bees in Twin Cities Metro Roadsides

Status:  Active
Project Start Date:  06/29/2017


A number of bumble bee species have recently experienced dramatic declines. For example, once relatively common in Minnesota, the rusty-patched bumble bee (Bombus affinis) is now listed as Critically Endangered by the IUCN. Similar losses have also been documented in other Minnesota species including the yellow-banded (B. terricola) and American bumble bee (B. pensylvanicus). The reasons for these declines are a combination of factors such as disease, pesticides, climate change and habitat loss - including reductions in floral resources and nesting sites. While all three of these species have been recently recorded in the Twin Cities metro area, reliable population estimates and rigorous assessments of habitat associations are lacking. Further, roadsides offer a unique opportunity to increase habitat for these declining species. However, little is known about whether B. affinis and other declining bees use roadsides. This research has four objectives. First, we will sample bumble bees in roadside areas at 30 survey locations systematically distributed throughout the Twin Cities metro area in an effort to detect the area occupied by B. affinis and other declining bumble bees and assess their use of roadside habitat. Sampling will be rapid and broad-scale giving relative abundances of bumble bee species, rather than estimates of absolute population sizes. Recent B. affinis sightings will be used to prioritize survey locations. Secondly, we will estimate population sizes of bumble bee species at eight of the 30 locations using a mark-recapture approach. This technique provides a more robust population size estimate. These sites will be chosen based on proximity to recent records of B. affinis. Third, we will compare rapid assessment and mark-recapture methods to develop a long-term monitoring protocol to be incorporated into the Minnesota Bumble Bee Survey and inform national bumble bee survey efforts (managed by Co- PI Evans). Fourth, we will characterize floral communities, land-use type and roadside management practices at survey locations. We will then examine whether these characteristics are related to variation in bumble bee population size and species composition.

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