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Saff Killingsworth, Conservation Biologist, Xerces Society for Invertebrate Conservation, (928) 487-0055, [email protected]

Rich Hatfield, Senior Conservation Biologist, Xerces Society for Invertebrate Conservation, (503) 468-8405, [email protected]


PORTLAND, Ore.; November 16, 2023—The Xerces Society for Invertebrate Conservation has submitted a petition for the U.S. Fish & Wildlife Service to protect Morrison bumble bee (Bombus morrisoni) under the Endangered Species Act.

Morrison bumble bee is found in the shrublands, grasslands, and woodland edges of 14 western states, from Washington to southern California and as far east as Texas and South Dakota. Despite its widespread distribution, the species is much less common than it was historically, and has not been recently found in many areas where it previously lived. It has been disappearing, and the likely causes include habitat loss and degradation, pesticide use, climate change, exposure to disease from managed bees used in agriculture, and inadequate protection across the states in which it is found.

“Morrison bumble bees play an important pollination role in wild and agricultural ecosystems across the West,” said Saff Killingsworth, an endangered species biologist with the Xerces Society. “If we lose this species, it could have far ranging consequences.” 

In 2015, the Morrison bumble bee was assessed as vulnerable on the IUCN Red List of Threatened Species, a non-regulatory designation separate from the federal Endangered Species Act. Recent analyses show that the species has continued to decline. 

In the last 10 years, its abundance relative to other bumble bees within its range has declined by 74%, and has not been recently detected in 66% of grid cells where it occurred historically. Relative abundance of Morrison bumble bees is considerably lower than it was historically in every place across its range where it is systematically monitored, including in California, Idaho, Oregon, and Washington. 

The decline of Morrison bumble bees is part of a broader trend seen across bumble bee species. More than one quarter of North American bumble bees are facing some degree of extinction risk. Some species that were once widespread and common have disappeared from parts of their ranges, or have been reduced to very low population numbers. 

“It is unfortunate that so many of our native bumble bees have declined to the point of needing Endangered Species Act protections,” said Rich Hatfield, senior conservation biologist for the Xerces Society and red list authority for the IUCN Wild Bee Specialist Group. “But, this law is incredibly effective at helping species recover when other efforts seem to be falling short.”

Morrison bumble bee joins several other species of bumble bees, including the western bumblebee bee and the rusty patched bumble bee, that face ongoing threats and warrant conservation attention. 

“Bumble bees are intrinsically valuable animals, having co-evolved with other plants and animals for thousands of years. Our world wouldn’t be the same without them,” said Killingsworth. 

Individuals who want to contribute to the recovery of Morrison bumble bees, including farmers, ranchers and private landowners, can learn more from the Xerces Society or visit the U.S. Fish and Wildlife Service website for more information on the petition process. Individuals who want to contribute to ongoing data collection efforts for this and other bumble bee species can visit Bumble Bee Watch and the Bumble Bee Atlas for more information.