Study from EID published in Nature shows effect of harsh winters on hibernation patterns

Harsh winters make hibernating squirrels go to ground for longer

A University of Edinburgh study just published online in Nature shows that hibernating squirrels in the Rocky Mountains are delaying emergence from their burrows when winters are severe, which is impacting on their population.

Columbian ground squirrels are already known to sleep for nine months of the year - but now changing climates are impacting on their populations by prolonging their hibernation, a study suggests.

Research into the small furry creatures, which live in the Rocky Mountains, has revealed that heavy winter snowfalls are delaying the animals' emergence from their winter burrows.

This could prevent female ground squirrels from gaining enough weight during their short summer to give birth to healthy offspring and to survive the next season's hibernation.

An international team of scientists led by the Universities of Edinburgh and Alberta studied Columbian ground squirrels in Alberta, Canada, which typically hibernate for eight or nine months of the year.

They found that the squirrels tended to stay underground for longer during winters with heavy snowfall. Over the 20-year study, late-season snowfalls increased, which kept the squirrels underground for an extra half-day per year on average.

Researchers found that in those years when squirrels emerged late from their burrows, both mothers and pups were less likely to survive. Overall, population growth has fallen over the two decades of the study. Scientists say their findings suggest that forecasts of worsening winters, if accurate, could lead to further population decline.

The study, published last week in Nature, was carried out in collaboration with the Centre d'Ecologie Fonctionelle et Evolutive in France and Auburn University in Alabama. It was supported by the Royal Society. 

Professor Loeske Kruuk, of the University of Edinburgh's School of Biological Sciences, and member of Edinburgh Infectious Diseases, said:

 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."

Dr Jeff Lane, of the University of Alberta, said:

This highlights the significance that changes in the climate can have on hibernation, and suggests that worsening winters pose a threat to the future populations of wild mammals."

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