Deadly ‘lie-in’ for squirrels as climate change hits hibernation

Squirrels: at risk from climate change. Picture: PA
Squirrels: at risk from climate change. Picture: PA
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CLIMATE change is having a deadly impact on hibernating mammals with late and severe cold snaps forcing them to rest up for too long, a new study warned yesterday.

Experts monitoring Columbian ground squirrels in the Rocky Mountains of Canada found that unseasonal, heavy snows in recent years have forced the animals to hibernate in their burrows for longer.

This jeopardises their survival because pregnant females don’t have time to eat enough to gain the weight needed to produce healthy offspring – and endure the next season’s hibernation.

An international team of scientists led by the universities of Edinburgh and Alberta, in Canada, found that as extreme and prolonged snowfalls increased, the animals tended to stay underground for an extra half-day a year on average. They were observed, trapped and released in a sub-alpine meadow.

The researchers noticed that in those years when the ground squirrels emerged late from their burrows, both mothers and pups were more likely to die. They suggested that the changing weather was the key cause of a 20 per cent drop in the survival rate of adult females observed over the 20-year study.

As the findings were published in Nature yesterday scientists warned that with winters set to get even worse the deadly effect on rodents such as ground squirrels was likely to increase.

University of Alberta evolutionary ecologist Jeff Lane explained that the squirrels have a very limited time in which to reproduce successfully with females mating just four days after emerging from hibernation and giving birth 24 days later. Newborns are nursed for 28 days, after which they are on their own.

“Losing just ten days – the progressive impact of losing half a day a year for 20 years – during their short active period reduces their opportunity to eat enough food so they can survive through the next hibernation period of eight to nine months,” he said.

Mr Lane added: “Our data shows that over the life of the study, the survival rate of adult females has fallen by 20 per cent, and much of this could be due to late emergence from their ­burrows brought on by late spring snowfalls.”

As a result the population which was studied has gone from “one of growth 20 years ago to its current state of just maintaining population stability”, he said.

Professor Loeske Kruuk, of Edinburgh University’s School of Biological Sciences, added: “Previous studies on the effect of climate change on animals have linked warmer temperatures to earlier timing of key events, such as birds breeding earlier in the year.

“This study reveals a different aspect of climate change – increased precipitation, in the form of heavy snow, is delaying the timing of a key aspect in the ground squirrels’ year.”

Researchers also warned that other hibernating animals face similar dangers.

Mr Lane said: “This highlights the significance that changes in the climate can have on hibernation, and suggests worsening winters pose a threat to the future populations of wild mammals.”