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Western Bumblebees May Be Poised For A Colorado Comeback

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Western bumblebee populations have decreased dramatically in recent years in states like Oregon, Washington and Colorado – making them increasingly rare in the west. They just might be on the verge of a comeback.

Recent survey results releasedTuesday by CU Boulder biologists are showing that their numbers are on the rise in the Centennial State.

Credit Patrick Campbell / University of Colorado
University of Colorado
CU-Boulder biologist Carol Kearns looks on as undergraduate researcher Benajamin Bruffey uses a vial to catch a bumblebee sitting on a thistle bloom. Bruffey is one of five undergraduate researchers who worked this summer on a bumblebee survey.

Researchers just completed year four of a five-year survey of the overall bumblebee insect population in Boulder County. While western bumblebees weren’t present the first two years, researchers identified nine of the insects in 2012 and more than a dozen in 2013.

“We’re hoping it does mean that they have made successful colonies,” said CU-Boulder Biologist Diana Oliveras, who is heading up the survey along with Biologist Carol Kearns. “Without more data it’s hard to tell.”

Earlier this summer the western bumblebee, known in Colorado for its distinctive white rump, was also spotted near Seattle. That indicates its numbers may be growing in other states.

The Seattle Times Reports:

Western bumblebees were once among the most common bumblebees in the Western United States. Then they began to vanish in the mid-1990s. No one knows for sure what is killing the species, but the decline coincides with the development of commercial bumblebee-breeding programs. Breeders sold colonies to tomato farmers in the United States and Europe. (bumblebees are the only native pollinators for tomatoes.)


Oliveras says next year will mark the fifth and final year of the population survey, which revisited nine separate locations at low, middle and high elevations in Boulder County.

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