Rare western bumblebees appear to be making a comeback

September 3, 2013

Sept. 3, 2013                                         Carol Kearns and Diana Oliveras

A white-rumped bumblebee that has been in steep decline across its native range in the western United States and Canada appears to be making a comeback on the Colorado Front Range.

A survey of bumblebee populations by CU-Boulder biologists Carol Kearns and Diana Oliveras in undisturbed patches of prairieland and in mountain meadows has turned up more than 20 rare western bumblebees in different locations.

Making the discoveries even more interesting is that the bees are most likely from several different colonies, says Oliveras.

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Rare western bumblebees appear to be making a comeback

Sept. 3, 2013                                         Carol Kearns and Diana Oliveras

A white-rumped bumblebee that has been in steep decline across its native range in the western United States and Canada appears to be making a comeback on the Colorado Front Range.

A survey of bumblebee populations by CU-Boulder biologists Carol Kearns and Diana Oliveras in undisturbed patches of prairieland and in mountain meadows has turned up more than 20 rare western bumblebees in different locations.

Making the discoveries even more interesting is that the bees are most likely from several different colonies, says Oliveras.

CUT 1 “These different plots are separated by quite some distance. So it suggests what we are looking at is not just one big colony but different colonies in these different areas. (:11) So for a bee that was considered to be maybe locally extinct the good news is that we found several different colonies.” (:19)

The western bumblebee has been in decline for the last couple of decades, says Oliveras.

CUT 2 “In certain areas, primarily in the United States, northern California, Oregon, Seattle and then heading into British Columbia, the populations of western bumblebees have just plummeted since the 1990s - particularly the late 1990s. (:16) In our area, in Colorado, there have been very few reports of these bees.” (:21)

The return of the western bumblebee is good news for the environment in general but especially for the agricultural community, says Oliveras.

CUT 3 “So if you have a resurgence of these pollinators it helps guarantee the success of the entire ecosystem. (:10) And from the standpoint of what these bees do, the western bumblebee, as well as many of these other insects, they’re really important pollinators for a variety of crops” (:21)

This is the fourth summer of a planned five-year survey in Boulder County. Although studies in the early 20th Century of bees and other insects along the Front Range led to the discovery of a variety of insects, Carol Kearns says there was no data telling them how many bees may have existed in the past. One of the goals of this survey is to establish that data for future studies.

CUT 4 “There is literature out that that suggests that pollinators, and bumblebees as pollinators, are in decline but here in the Front Range we don’t really have abundance data.(:11) We have a lot of information going back to 1900 on what species of insects, not just bumblebees, but what species of insects occur in this area. So we thought: How can we possibly tell if bumblebees are in decline if there is no abundance data to begin with?” (:27) 

According to Kearns and Oliveras, several factors have been implicated in the decline of the western bumblebee. The biggest suspect is a non-native parasite that may have been transmitted from commercially raised bumblebee colonies.

 

-CU-

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