For four summers, University of Wyoming researcher Christy Bell scoured Wyoming for western bumble bees — furry black and yellow insects with distinctive white tails.
She set traps — colorful contraptions that mimic flowers — in areas where western bumble bees had historically been recorded and other places where they should have been. She was one of the first researchers to actually look for western bumble bees in the state. And she didn’t find many.
In fact, though actual population models for Wyoming are yet to come, her preliminary data show that western bumble bee habitat has declined by almost 70% across the state.
Researchers know more about the rest of the West, and the outlook is even worse. Populations of the once-common bee — whose habitat seemed to be wide ranging — have shrunk by a shocking 93% in just over 20 years, Bell and a host of co-authors revealed in a study published in June.
Populations are so dire that the U.S. Fish and Wildlife Service is researching whether the western bumble bee should be placed on the endangered species list. The Suckley’s bee is also being considered for listing. But in a strange twist, the Suckley’s bee (also native to Wyoming) survives by preying on western bumble bee hives.
One thing researchers are sure of: the role of bees in food production is essential.
“Bumble bees are generalist pollinators, which means they will pollinate a bunch of different kinds of flowers,” said Lusha Tronstad, an invertebrate zoologist with the Wyoming Natural Diversity Database who also studies western bumble bees. “If we don’t have the bees out there pollinating, we won’t have food for us or wildlife. They’re integral to most plants’ reproductive cycles.”
Like many insects, we just don’t know nearly enough about the western bumble bee.
Some studies show the planet likely houses up to 10 million species of insects, but we only have a fraction of that number actually categorized. The bulk of the world’s insect diversity is in the tropics, which experts say is woefully understudied.What scientists do know is that many insect populations are plummeting. A newly published special issue of the journal Proceedings of the National Academy of Sciences highlighted that the number of insects in portions of the world are declining by 1% to 2% a year.
Combined, that could equal a loss of up to a third of all insects over a decade in some places.
Major contributors to the decline include climate change, industrialized agriculture, pesticide use and even light pollution.
In Wyoming, one of the largest stressors is likely parasites, Bell said.
Western and eastern bumble bees (relegated to the western and eastern half of the U.S. as their names imply) were once collected and sent to Britain to be bred and used in pollination. Bumble bees are particularly good at pollinating crops such as blueberries, tomatoes and cranberries because of a motion called “buzz pollination.”
“The bee lands on the flower and vibrates its flight muscles, shaking the flower and the pollen comes out,” Bell said. “If you see a bee, watch it. The buzz pollinating is a higher-pitch buzz. It’s so cute.”
However, when some bumble bees were returned to the U.S. from overseas, they came bearing parasites at higher loads than they’d evolved to fight. The eastern bumble bee seems to be able to survive with that load, but the western bumble bee doesn’t.
Researchers aren’t sure why. It’s one question that UW undergraduate researcher Maxwell Packebush is focusing on.
He spent the summer of 2020 collecting bees around the southeast corner of the state, dissecting them and analyzing DNA samples of the organisms living in the bumble bee’s guts. After analyzing 75 bees, he found all of them had parasites of some kind. But experts still don’t know which of those parasites are deadly and why.
“All of us have pathogens in us all the time, but we have to figure out what the pathogens are and also the pathogen load,” Bell said, because some pathogens are likely outright killing the bees, while others may be simply taking up too much space inside the host.
And those just scratch the surface of questions on western bumble bees.
The U.S. Fish and Wildlife Service originally planned to have a draft status assessment of the western bumble bee completed by spring of 2022, said Doug Keinath, recovery coordinator with the service’s Wyoming field office.
The agency is reviewing the best available science, modeling population viability and analyzing stressors to the species to better understand if a listing is warranted.If the bee is listed, that comes with protections. Still, those likely won’t affect most of us.
“Like a black-footed ferret or a grizzly bear, even if you’re on your private land, you couldn’t go out and shoot them,” Keinath said. “If you saw a bumble bee colony on your land, you couldn’t gas or poison it.”
But you would be able to, for example, turn your back 40 acres from natural area to an alfalfa field.
A listing could also spur habitat improvement projects in a state like Wyoming, Keinath said.
Conservationists, meantime, recently petitioned for the Suckley’s to be listed. The Suckley’s is also called a cuckoo bee because it survives by invading a bumble bee nest, killing the queen and forcing the workers to raise its young. It is, in effect, a parasite.
It’s also not doing well.
“You’ve petitioned a predator and its prey simultaneously for listing,” Keinath said. “How does that work?”
In the meantime, experts stress that people can help native bees. Wyoming alone has 25 native bumble bee species. They could all benefit from less pesticide use, more native plants and people who leave their yards just a little messy in the winter.
Queen bees nest underground or even in dead and decaying leaves. Leaving those behind — and waiting until after April to dig up the ground — means more queens will survive into summer to reproduce.
Honey bees, which are not native to the U.S., carry parasites that can be fatal to native bees. They also compete with native bees for food.
And lastly, people can help by reporting bee sightings to apps like iNaturalist or Bumble Bee Watch, which keep track of verified insect locations. The more data experts have on the species, the easier it will be to work on conservation.
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