Center for Biological Diversity

For Immediate Release, May 10, 2021


Tara Cornelisse, (510) 844-7154,
Jess Tyler, (406) 366-4872,

Suckley’s Cuckoo Bumblebee Takes Step Toward Endangered Species Act Protection

Highly Imperiled Bumblebee Has Declined More Than 90%

PORTLAND, Ore.— The U.S. Fish and Wildlife Service announced today that Suckley’s cuckoo bumblebee, a critically imperiled species that has recently declined by more than 90%, may warrant Endangered Species Act protection. The announcement kicks off a one-year status assessment of the species.

Today’s positive finding comes in response to a petition filed in 2020 by the Center for Biological Diversity. This would be the first cuckoo bumblebee protected under the Act and the second bumblebee, with the rusty patched bumblebee being the first.

Suckley’s cuckoo bumblebee was once common in prairies, grasslands and meadows across the West but has lost more than 50% of its historic range to grazing, pesticides, habitat loss, competition and disease threats from non-native honeybees and global warming. The last sighting of the bee was in Oregon in 2017. Over the past two decades a few scattered individuals have been spotted in California, Alaska, Idaho, Oregon, Colorado, Wyoming and Montana.

“This is a first step toward preventing the extinction of this important cuckoo bumblebee, but its survival depends on quickly getting the Endangered Species Act’s full protection,” said Dr. Tara Cornelisse, a Center senior scientist and petition author. “These intriguing, parasitical bumblebees play an important role in maintaining the health and diversity of the bumblebee community.”

“Cuckoo” bumblebees are social parasites that take over the nests of other bumblebees by subduing the resident queen and making the worker bees feed and care for their own young. In doing so, cuckoo bumblebees help keep host bumblebee populations diverse and healthy, including by reducing disease virulence.

For Suckley’s cuckoo bumblebees, successful reproduction is closely intertwined with the welfare of their main known host, imperiled western bumblebees. Western bumblebee populations across the West are approximately 57% below historic estimates. The Center is fighting to ensure western bumblebees also receive protection under the Endangered Species Act.

“The dramatic decline of the Suckley’s cuckoo bumblebee was caused by human behavior and can be turned around by that same force, but we need the Biden administration to act fast to save our pollinators before it’s too late,” said Jess Tyler, a petition author and staff scientist at the Center. “By protecting the bee under the Endangered Species Act, we can ensure its remaining habitat is managed to head off extinction.”

The Service will now initiate a scientific status review and public comment period before making a final decision on whether to protect the bumblebee.


The decline of the Suckley’s cuckoo bumblebee is part of a troubling downward trend in many of the 46 species of bumblebees and approximately 3,600 species of native bees in the United States that are needed to pollinate the full spectrum of wild plants. A generalist pollinator, it’s one of a rare group of parasitic cuckoo bumblebees that play important regulatory roles in bumblebee communities and ecosystems.

While their specific methods are yet unknown, female Suckley’s cuckoo bumblebees must fight or sneak into a host colony, then kill or subdue the host queen. The cuckoo bee then lays her own eggs and controls the workers to continue collecting pollen and nectar to provision her offspring, often via aggressive behavior and chemical cues.

Suckley's cuckoo bumblebee occurence, Center for Biological Diversity. Image is available for media use.

The Center for Biological Diversity is a national, nonprofit conservation organization with more than 1.7 million members and online activists dedicated to the protection of endangered species and wild places.

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