For Immediate Release, April 23, 2020


Tara Cornelisse, (971) 717-6425,

Endangered Species Act Protection Sought for Suckley’s Cuckoo Bumblebee

Habitat Destruction Helps Drive 90% Decline Across Western States

PORTLAND, Ore.­— The Center for Biological Diversity petitioned for Endangered Species Act protection today for the critically imperiled Suckley’s cuckoo bumblebee, which has declined by more than 90%.

The rare parasitic pollinator was once common to prairies, grasslands and meadows across the West but has lost more than 50% of its historic range to grazing, pesticides, habitat loss 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.

“Without immediate protections, this unique native bee could be lost forever,” said Dr. Tara Cornelisse, an entomologist and senior scientist at the Center. “By saving this cuckoo bumblebee, we can restore a vital species and help protect these disappearing ecosystems.”

The nearly inch-long, black-and-yellow bee is unusual in that it is a “cuckoo” or social parasite that takes over the nests of other bumblebees by subduing the resident queen and making the worker bees feed and care for its own young. In doing so, cuckoo bumblebees help keep host bumblebee populations diverse and healthy, including by reducing disease virulence.

Over the past 20 years, Suckley’s cuckoo has only been found a handful of times per year, with the last confirmed sighting of one individual three years ago, despite increased research and survey efforts.

The bee is also threatened by loss of host species. Its successful reproduction is closely intertwined with the survival of other rare bumblebees, particularly the imperiled western bumblebee.

Western bumblebee populations across the West are about 57% below historic estimates. The Center is fighting to ensure it also receives protection under the Endangered Species Act.

Both the Suckley’s cuckoo bumblebee and its hosts were once widespread across western grasslands now mostly converted to housing and agriculture. In general, bumblebees need between 350,000 and 18 million flowers per month over an area of about 250 acres to successfully reproduce. When prairies and meadows are destroyed, bumblebees do not get adequate nutrition and calories through the growing season.

Due to habitat loss, Suckley’s now mostly survives on public land, where it is still threatened by grazing, over-use of pesticides and fire suppression.

“The dramatic decline of Suckley’s cuckoo bumblebee is a telltale sign that the western bumblebee community as a whole is in urgent need of our help,” Cornelisse said. “By protecting the bee under Endangered Species Act, we can ensure that its remaining habitat is managed for the survival of these incredible species that make our natural world such a fascinating place.”


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.

Suckley’s cuckoo bumblebee is a generalist pollinator and represents a rare group of obligate parasitic cuckoo bumblebees that play important regulatory roles in the bumblebee community and ecosystem.

While specific methods are 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 and its main known host, the western bumblebee, are both highly imperiled and in need of protection under the Endangered Species Act. The two species are also currently candidates for protection under the California Endangered Species Act.

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.