Creatures vs. climate: The snowshoe hare

The snowshoe hare changes colour to match the snow, but warming weather is throwing its camouflage out of sync — and that leaves it vulnerable to predators
By Tim Alamenciak - Published on September 17, 2018
Snowshoe hare jumping through snow.
The snowshoe hare is one of 21 species that change colour according to the season. (iStock.com/impr2003)

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Snowshoe hares are in a race for their lives.

The creatures, widespread across the boreal forest, have a peculiar camouflage mechanism — they’re one of 21 species that change colour according to the season. In the warm months, they’re a ruddy brown, and in the winter months, they turn white.

The camouflage is remarkably effective at keeping them alive, but climate change is causing this effect to be out of sync with the seasons.

Their coat change is determined by the length of the day, which has remained constant. Snow cover, however, is determined by the temperature, and it’s dwindling because of the warming climate. This means that some hares are turning white before the ground does, leaving them vulnerable to predators.

“As my one grad student says, having the wrong wardrobe can be deadly,” says Scott Mills, professor of wildlife biology at the University of Montana.

The hares themselves don't realize they're mismatched. So when predators come by, they simply sit there, thinking they’re camouflaged when, in fact, they’re all too visible to a hungry lynx.

Mills and his lab have been studying the mismatch and its effects on populations of snowshoe hares. They’ve found that being mismatched increases a hare's likelihood of being killed by 7 per cent in a given week.

The number may seem small, but would you get on an airplane if its chances of falling out of the sky suddenly increased by 7 per cent?

Snowshoe hares are numerous, and, so far, the mismatch hasn't led to a decline in their populations — but that doesn't mean it won't happen down the road.

"The optimistic side is, we don't yet see population collapses; the serious side is, we're going to have to take some actions. Otherwise, we can be pretty confident that over the next half-century, there will be a good chance mismatch could lead to decline," says Mills.

Snow cover has been shrinking in Canada. From 1972 to 2010, the average annual area of snow cover in Canada declined by 5.1 per cent. The effect is the worst in the spring months — April shows a decline of 7 per cent, May of 13 per cent, and June of 34 per cent over the same period.

But there is hope for the animal. The colour change is triggered by a single gene. Given the right conditions, snowshoe hares can adapt to meet the new climate.

"If a trait is genetically based and a population is large, then it is possible to see rapid evolutionary change within five to 10 generations," says Mills. "I'm not saying evolution is magic ... What I'm saying is we need to understand the scope for rapid evolutionary change and use that to guide management actions."

The key to furthering such change is supporting a large, contiguous population — something that has been a staple of conservation efforts.

"What this does is brings evolution to the table and says those kind of old-fashioned conservation actions are absolutely critical for fostering the ability of all species to endure rapid environmental change," says Mills.

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