By John R. Platt
I’ve seen some big bumblebees in my time, but nothing like South America’s Bombus dahlbomii. “It looks like a flying mouse,” says Sarina Jepsen, endangered species program director for the The Xerces Society for Invertebrate Conservation. “It’s huge, colorful and incredibly charismatic.”
B. dahlbomii is, in fact, the world’s largest bumblebee. Native to the Patagonia region of Argentina and Chile, the queens of the species can reach an amazing four centimeters in length. That’s eight times the size of one of the most recognizable North American species, the American bumblebee (B. pensylvanicus).
The Patagonian bumblebee’s notable size doesn’t offer them much protection, though. Over the past decade the species has been wiped out from much of its historic range. It’s unknown exactly how many remain.
So how did this massive species disappear in such a small amount of time? To answer that question, we need to go back to 1997. That’s the year that two European bumblebee species—large garden bumblebees (B. ruderatus) and buff-tailed bumblebees (B. terrestris)—were imported to Chile for the purpose of pollinating greenhouse agricultural crops. Some of the bees spread to the wild and they reached Patagonia in 2006.
That’s when the devastation started. Not only did the buff-tailed bumblebees present some competition for the native variety, they were also infected with a parasitic protozoan called Apicystis bombi that, as you might guess from its name, targets many honeybees and bumblebees. The parasite—which does not appear to afflict the buff-tailed bumblebees—infects the guts, then spreads to other parts of the body. Still poorly understood, it appears to cause behavioral changes that result in a high level of worker bee mortality and slows the establishment of new colonies.
“We need immediate action to help these bumblebees,” Jepsen says. The most important first steps will be to figure out how the pathogen is being transmitted among B. dahlbomii and how the invading species are competing with the natives for food and habitat.
The work to find that information begins soon. The International Union for Conservation of Nature (IUCN) has launched a fundraising campaign to help raise the money necessary to evaluate the health and risks of B. dahlbomii and 100 other little-studied bumblebee species. “Funding is difficult to come by and we need to fast-track the process,” says Paul Williams, chair of the IUCN Bumblebee Specialist Group. He says the group already has some funding but the outreach will help to fill the gap (they seek $25,000) and also serve to engage the public in the plight of the world’s bumblebees.
Meanwhile Jepsen worries about pathogens like this spreading to other species as bees are imported from country to country and continent to continent. She’s not alone; a 2013 paper published in the Journal of Applied Ecology warned that more than a million commercial bumblebee colonies are imported worldwide every year. Tests on colonies from three producers found that 77 percent of them carried microbial parasites, including A. bombi. The researchers dubbed the problem “Trojan hives.” As a result of that paper, the British Ecological Society and Bumblebee Conservation Trust called for strict controls of bumblebee imports in order to protect the U.K.’s native bees.
It’s obviously too late for new controls to protect the “flying mouse,” but research by the IUCN’s bumblebee team will now seek to find out how endangered the species has become. Hopefully in the process they can come up with solutions to help save it.