Despite being featured on the Canadian 25-cent coin—the ideal currency for purchasing jawbreakers at the movie theatre—woodland caribou populations have been steadily decreasing. They're listed as a threatened species in Canada's Species at Risk Public Registry.
Caribou are facing a lot of threats. On top of hunting and habitat destruction, invasive species play a large role in the caribou's decline, according to Robert Serrouya, a professor in the Department of Biological Sciences at the University of Alberta. Managing these species, including moose and white-tailed deer, could also be the key to stabilizing the caribou population, according to his new study published in PeerJ.
Woodland caribou are found in western Canada, but some herds go as far east as Newfoundland and Labrador. These large antlered mammals are part of the Cervidae family, which includes deer and moose as well.
Climate change and industrial logging are disrupting the caribou's population, but the species that replace large trees—like willow and aspen—attract non-native moose and deer. And the increased number of prey in turn increases the wolf population, and they kill off more caribou.
"They get taken out by those predators because they can't deal with the same level of predation that moose and deer can," Serrouya said in a phone interview.
He told me that culling the wolf population would help stabilize the caribou, but it's not as socially acceptable to kill wolves en masse anymore, and it doesn't really get to the root of the problem—that the habitat is changing and the wolves are just a byproduct of that change.
The solution that Serrouya and his team came up with is to reduce the moose population back to what it was before the habitat changed, through sport hunting—moose are classified as a species of "least concern" when it comes to going extinct, and are legal to hunt across Canada. He found that in the environments where they reduced the number of moose, the wolves dispersed too. They noted a higher survival rate for caribou than in habitats where they didn't.
"If you think of it as a three-step chain—the vegetation, the moose, and then the wolf—the further down you go into the chain, closer to the habitat, the more you're dealing with the ultimate cause," Serrouya said in a phone call.
Serrouya said that environments are connected in ways that we don't always expect, which is why they wanted to try this more indirect method to protect caribou.
"If you reduce wolves directly, that's a more predictable result. But it's not popular, and it's just a band-aid solution. Dealing with moose and dealing with habitat, it's a more complicated and interconnected approach," Serrouya said.
Though reducing the population of invasive species that increase the number of predators in the area has successfully stabilized some caribou populations in western Canada, Serrouya said that it's not enough to ensure that the caribou herds begin thriving again. To do that, we need to protect their habitat from climate change and deforestation as well.
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