Seattle Project Highlights Role of Declining Bumblebees

Jul 18, 2013

The plight of honeybees is well-known. Their numbers are dropping, and entomologists are trying to figure out the cause. But did you know that bumblebees—the larger, slower, and furrier relatives of the honeybee—are also in trouble?

A project in Seattle, called the Urban Pollination Project, is trying to show how important bumblebees are for pollinating food. That ripe juicy tomato in your salad was likely made possible by bumblebees. 

A bumblebee at work at the the Picardo Farm P-Patch in North Seattle.
A bumblebee at work at the the Picardo Farm P-Patch in North Seattle.
Credit Jennifer Wing / KPLU

Marie Clifford, a biology graduate student at the University of Washington, is a co-founder of the Urban Pollination Project. She says bumblebees have a unique way of getting pollen out of a flower. They don't just crawl around; they vibrate by shaking their bodies.

"And that can release pollens from certain kinds of flowers like tomato plants. And honeybees can't do that. Honeybees can't pollinate tomato plants at all."

The UPP is collecting data from small tomato gardens all over the city. In the experiment, two tomato plants are out in the open. One of them gets some extra help from a musical tuning fork. Susan Waters, the other co-founder of the project, says it mimics a vibrating bumblebee. 

"I'm going to  hit the tuning fork on my hand to make it vibrate, and then I'm going to touch it to one of the tomato flowers. And if the flower is ready to release pollen, this little puff of pollen will come out. And that is what happens when a bumblebee buzzes it."

A musical tuning fork mimics how bumblebees "buzz pollinate" flowers. They shake their bodies inside the flower, something  honeybees can't do.
A musical tuning fork mimics how bumblebees "buzz pollinate" flowers. They shake their bodies inside the flower, something honeybees can't do.

The plants that get touched by the tuning fork produce the greatest number of tomatoes. Waters and Clifford say this shows how yield would improve if there were more bumble bees around.

As far as what's causing bumblebee populations to shrink, and some to disappear, scientist say a fungus from European bumblebees  might be a culprit, as well as a loss of habitat.

Meanwhile, there's some good news for the bumblebee world in Washington State. Bombus Occidentalis, a species native to Western Washington also called the Western Bumblebee, hasn't been seen since the mid 1990s. It has a distinctive white bottom. But in the last few weeks, Susan Waters says a queen was spotted in Mountlake Terrace.

"She was foraging on introduced Himalayan Blackberry. It wasn't like this nice native bee was out foraging on all the native species that we like to protect," she said.

Researchers will keep an eye on the area next spring looking for the tell-tale white bottoms to see if the queen was successful in raising a new brood.