Yukon's mild winter weather may affect wildlife

Yukon's mild temperatures might make winter more enjoyable for people, but it's a mixed bag for wildlife in the territory.

Biologist says warm winter poses challenges for some animals, benefits others

Caribou near the Dempster Highway last fall. (Heather Avery/CBC)

Yukon's mild temperatures might make winter more enjoyable for people — particularly when it means less shovelling and risk of frostbite — but it's a mixed bag for wildlife in the territory. 

Tom Jung, a wildlife biologist with Yukon's department of environment, says animals are impacted by weather in different ways. 

"Really, with these things, there's winners and there's losers," he says.

The 'winners'

Jung says the equation for surviving winter in the North is simple: "Energy in, energy out."

The more energy animals use trying to stay warm, the more they have to eat in order to keep up their fat reserves. 

Animals that depend more on their own actions to survive winter are more likely to benefit from mild temperatures, Jung explains.

That includes red squirrels and porcupines, which don't have a lot of physical characteristics such as warm winter coats, or physiological ones, such as the ability to slow down their heart rate, to survive. 

"They don't really have the other means to deal with it other than to try to avoid the cold behaviourally," says Jung. "If they don't have to avoid [the cold] they can go about their business and save their reserves and get through the winter a little easier." 

The 'losers'

A Yukon biologist says a recent warm spell has created a hard crust of ice in the southern territory which could cause problems for moose and caribou. (CBC)
Jung says he hears from people who spend a lot of time on the land that caribou and moose have difficulty with warm weather, particularly when there is a freeze/thaw cycle. This hardens the snow and creates a top crust that makes it difficult for ungulates to run and walk.

That's good new for the wolves stalking moose and caribou because, unlike their prey, wolves are often not heavy enough to break through the crust.   

The dense, icy snow also makes it harder for caribou to dig underneath to access their main food source, lichen. 

Mild winters can affect smaller animals too, says Jung.

Melting patches on the ground don't do any favours for the snowshoe hare, which has a white coat in the winter. 

"We start getting white bunnies on brown patches and predators can notice them more."

Bears waking up early? 

A Yukon biologist doesn't think bears will come out of hibernation early this year, despite the territory's mild late-winter temperatures. (CBC)
Although Yellowstone National Park in Wyoming says the "relatively mild winter" may be to blame for at least one of its bears coming out of hibernation a month earlier than usual, Jung says it's doubtful Yukon bears will follow suit, even if the mild temperatures persist.

Sometimes bears will arouse in response to the temperature, but the decision "to come out and stay out" is mostly based on food availability, he says. 

"We might see the odd bear that pokes its head out but I don't think they'll stick around because, quite simply, there's nothing for them to eat."

It's not unusual, even during really cold spells, for bears to temporarily leave their dens in the winter, Jung adds. 

Bears in the territory generally feed on roots and animal carcasses in the early spring. 

Jung says they typically start leaving their dens for good at the end of March or in early April. 

Warm weather not 'the norm'

Despite some animals seeming to benefit from the warm temperatures, Jung is quick to point out that Yukon's mild late-winter weather is not "the norm."

"Its an indication of a warming climate that both people and local wildlife will need to adapt to," he says.

"Some will have little difficulty adapting, while others will be significantly challenged to do so in a timely manner."


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