Field Notes

The California Endangered Species Act Now Protects Four Bumblebee Species

Home  /  Field notes   /   The California Endangered Species Act Now Protects Four Bumblebee Species

As of September 30, 2022, four species of bumblebee native to California are listed as candidate species under the California Endangered Species Act (CESA). As candidate species, they are temporarily afforded the same protections as state-listed species during the listing review process. Crotch bumblebee (Bombus crotchii), Franklin’s bumblebee (B. franklini), western bumblebee (B. occidentalis), and Suckley’s cuckoo bumblebee (B. suckleyi) are now the first insects to be protected under CESA, although some aquatic invertebrates are already protected. This decision follows a series of court rulings around the uncertainty whether CESA can protect and list terrestrial invertebrates; however, the California Supreme Court has determined terrestrial invertebrates can be listed under CESA.

As candidate species, impacts to these species are considered significant under the California Environmental Quality Act (CEQA) and any take of the species, as defined in CESA, would require an Incidental Take Permit (ITP) from the California Department of Fish and Wildlife (CDFW). Projects with potential to impact these species should develop measures to reduce impacts to less than significant levels.

Crotch bumblebee habitat at the Petersen Ranch Mitigation Bank site in Los Angeles County.

Projects located within the range of these species and with suitable habitat should consider whether they have potential to occur within the project area. Western bumblebee and Suckley’s cuckoo bumblebee occur in central and northern California, Crotch bumblebee occurs in central and southern California, and Franklin’s bumblebee occurs between the Coast and Sierra-Cascade Ranges in Siskiyou and Trinity counties.

The four candidate bumblebee species occur primarily in grassland and scrub habitats, although western bumblebee and Crotch bumblebee have also been documented in urban parks and gardens, and cropland. Nests are commonly found underground, in abandoned rodent burrows, or aboveground in grass tufts, rock piles, abandoned bird nests, or tree cavities. Bumblebees feed on pollen and nectar and require flowering plants from late winter through fall.

If your project occurs within the documented range of these species and may contain suitable habitat, WRA invertebrate biologists can assist in determining whether suitable habitat is present within your project area, conducting surveys, and crafting mitigation measures. If a records search indicates that a listed species has been documented in the vicinity of your project, protocol-level surveys should be conducted to determine whether your project has the potential to impact these species. Protocols consist of four equally-spaced surveys in the summer/early fall. If a candidate species is observed during the surveys, further mitigation measures may be required to reduce impacts to less than significant and an ITP may be required. Mitigation for CEQA could consist of wildflower plantings to support bumblebee populations; however, if an ITP is needed, additional mitigation may be required and CDFW is anticipated to issue guidance later this year.

The review process to determine if each species should become formally listed can take between one and three years. As these bumblebee species are only recently listed as candidate species under CESA, currently no mitigation bank options exist for these species. WRA is currently assisting in the effort to explore crediting habitat for Crotch bumblebee at Petersen Ranch, an approved mitigation bank for wetlands, streams, riparian habitat as well as Swainson’s Hawk foraging habitat and native habitats under CEQA.

For more information contact WRA’s bee expert, Rei Scampavia, PhD (, or reach out via our contact form if have questions on the implications of the proposed listing.