EDMONTON — Research from the University of Alberta suggests that squirrels in the province’s southern foothills are starting to suffer from climate change.
The finding raises questions about what’s happening with other wild populations in the area.
“There’s reason to expect these patterns could be general across some different mammals,” said Jeff Lane, an ecologist whose paper was published Wednesday in the prestigious journal Nature.
Lane and his colleagues looked at a patch of subalpine meadow southwest of Calgary where a population of Columbia squirrels had been extensively surveyed and studied going back to 1992. To survive the area’s harsh winters, the tiny mammals hibernate between eight and nine months of the year.
But data showed the squirrels were waking up from their winter nap later and later every year. The average date of emergence was fully 10 days later in 2011 than in 1992.
The question was why?
Previous studies suggest that hibernating animals wake up when the weather gets warmer and the snow disappears. Temperature records in the area show that average temperatures haven’t changed much over the last two decades, so Lane looked at snowfall data.
Sure enough, late-season dumps of snow have become more common.
In the first decade of the study, there was only one year where more than five centimetres of snow fell after mid-April. In the second decade, there were seven such late snowstorms.
That lines up with standard climate change models, which predict more winter precipitation coming in more frequent heavy snowfalls across much of North America.
That spells trouble for the Columbia squirrels, which have a narrow window of just a few months to mate, raise their babies, then bulk up for the next winter’s hibernation.
“It’s just like a bank account,” said Lane.
“For a hibernating animal like a ground squirrel, they’re kind of like seasonal workers. They have to fill up their bank account with energy during the summer and then they will draw on that bank account when they are inactive for the winter.
“They’re delayed to start earning an income in the summer ... Their energy balance has tipped.”
The changes are showing effects in the overall population of squirrels in the study area.
During the first 10 years, there was only one year in which numbers declined. During the second half of the study, squirrels declined in four out of nine years.
Lane said his study shows that animals respond to other aspects of climate change than just temperature. Larger, non-hibernating animals such as elk and bighorn sheep could be experiencing a squeeze on their own energy bank accounts as well, he suggested.