July 9, 2010 | 11
Biologists in Canada are encouraged that critically endangered Vancouver Island marmots (Marmota vancouverensis) are once again learning how to be marmots—a tough task since the species’s population had crashed so far that the animals almost lost the knowledge of how to exist as a society.
In a classic example of what is known as the Allee effect, the Vancouver Island marmots experienced a social meltdown when their numbers declined, which in turn made it harder for the species to stay alive. The Allee effect was first postulated in 1931 by zoologist Warder Clyde Allee, who proposed that when a species’s population crashes, so will its societal structure, making it more likely to go extinct.
This rare marmot is one of the world’s most critically endangered mammals. After nearly going extinct a few decades ago, M. vancouverensis benefited from a captive breeding program hosted at the Toronto Zoo and other institutions, but it hasn’t been an easy road. The population has fluctuated from 25 to 30 animals to 300, then down to 75. Today, approximately 210 live in the wild.
According to Justin Brashares, co-author of a new study published in the June 9 online edition of the Journal of Animal Ecology, marmot colonies used to rely on the group to warn one another about the presence of predators. But a few years ago there were only 25 wild Vancouver Island marmots spread out over a 200-hectare preserve. “So what happens when there’s only one member in a colony? There’s no one watching your back, basically,” Brashares told the Victoria Times Colonist. Brashares conducted this research while he was affiliated with the University of British Columbia. He is now an assistant professor of wildlife ecology at the University of California, Berkeley’s College of Natural Resources.
During the course of a five-year study between 2001 and 2005, Brashares and his team found that as marmot numbers decreased, they were less likely to communicate with one another, and more likely to be aggressive toward their fellows. As a result, their predation rate increased. The marmots were also more likely to wander great distances (sometimes crossing two mountains) in search of other marmots, which weakened them and make them even easier targets for predators. Furthermore, the animals need to hibernate together to increase their chance to surviving through winter.
Luckily, more and more M. vancouverensis are being reintroduced into the wild (another 80 to 90 captive-bred marmots are due to be released this summer)—and they are finally breeding in natural conditions, which they weren’t doing a few years ago. “We can now test whether they’ll regain their sociality, whether they’ll remember to do alarm calls,” Brashares said.
According to Don Doyle of the Marmot Recovery Foundation, signs are already good. “Now we’ve reestablished some of the colonies to larger sizes and we’re getting all kinds of whistling and normal behavior,” he told the newspaper.
Image: The Vancouver Island marmot, via the Marmot Recovery Foundation