Beavers on the tundra? Yukon biologists see the unexpected

Flying over the tundra on Yukon's vast north slope in 2015, government biologist Tom Jung looked out his window and did a double take.

He and fellow biologist Dave Mossop were looking for peregrine falcons as part of a monitoring program, but Jung spotted something different, and unexpected — a beaver dam, on the Babbage River in Ivvavik National Park.

"I said, 'hey Dave, have you ever seen a beaver dam?' Because I thought it was a little odd," Jung recalled. "He had said he hadn't, so that got me thinking that this was a bit of a unique observation."

The two biologists helped co-author a report recently published in the journal The Canadian Field-Naturalist, about what they saw.

It turns out, their observations weren't completely unique — Inuvialuit hunters first reported seeing beavers in the area a decade ago. 

But such sightings are a relatively new phenomenon. 

'Shrubification' and climate change

Beavers have a vast range across North America, but are not typically seen on the treeless tundra. The dam spotted by Jung and Mossop was made with shrubs. 

"Beavers are quite adaptable and they can use different materials to make dams," Jung said. "We have seen, in the Yukon, them using rocks to build their dams, and other things."

The biologists aren't sure how or why the beavers have moved into the area, but they say Yukon's coastal plain is seeing more "shrubification", a consequence of climate change in the Arctic.

"Beavers are what we call a 'keystone species' — they're one of those species that can modify habitats for other species," Jung said. 

He says beavers on the coastal plain could have an impact on other species, by damming rivers that fish use to spawn.

"In the natural world, change is good for some species and not so good for other species," he said.