Monitoring and habitat assessment of declining bumble bees in Twin Cities metro roadsides

Principal Investigator(s):

Daniel Cariveau, Assistant Professor, Entomology


Project summary:

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 International Union for Conservation of Nature and listed as "endangered" with the U.S. Fish and Wildlife Service. Similar losses have been documented in other Minnesota species including the yellow-banded (B. terricola) and American bumble bee (B. pensylvanicus). The reason for these declines is 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, but little is known about whether B. affinis and other declining bees use roadsides. This research has four objectives. First, researchers are sampling bumble bees in roadside areas using randomly selected survey locations distributed throughout the Twin Cities metro area. The aim is to detect the area occupied by B. affinis and other declining bumble bees using occupancy modeling. Sampling is rapid and broad-scale, giving relative abundances of bumble bee species rather than estimates of absolute population sizes. Recent B. affinis sightings are being used to prioritize survey locations. Second, researchers are estimating population sizes of bumbleb ee species using N-mixture models--an analysis tool that uses count data to estimate population size. Third, researchers are comparing results from occupancy and N-mixture models 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-Principal Investigator Evans). Fourth, researchers are characterizing floral communities, land-use type and roadside management practices at survey locations. The study will then examine whether these characteristics are related to variation in bumble bee population size and species composition.

Project details:

  • Project number: 2018003
  • Start date: 06/2017
  • Project status: Completed
  • Research area: Environment and Energy
  • Topics: Environment