Spring blizzards disrupt hibernation pattern; survival rate drops by 20 percent
By Summit Voice
SUMMIT COUNTY — Although there is an overall trend of decreasing spring snow cover in the northern hemisphere, some areas have been hit by unusual late blizzards. Now, University of Alberta biologists have documented how those late storns in the northern Rockies are changing the hibernation patterns of Columbian ground squirrels, with a potentially deadly effect.
Spring blizzards had delayed the animals’ emergence from hibernation by 10 days over the last 20 years, disrupting the delicate balance of breeding and the availability of food sources.
“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,” said Jeff Lane, an evolutionary biologist at the university.
The researchers said the study area’s population has gone from one of growth 20 years ago to its current state of just maintaining population stability. The ground squirrels are on a tight schedule; females mate four days after emerging from hibernation. They give birth 24 days later. The newborns are nursed for 28 days, and then they’re on their own.
“Losing just 10 days 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.
Research shows there’s little wiggle room in the ground squirrel’s life cycle. The period of plant growth, their food supply, is only three to four months long on their home turf, skirting the Rocky Mountains.
The study area is a 200-meter by 400-meter block in a sub-alpine meadow west of Calgary. The data was collected through observation and by trapping and releasing all the ground squirrels in the study area to monitor their condition.
The study area was set up by U of A biologists in 1992. Lane began his hibernation study five years ago and collaborated with researchers in Scotland, France. Lane was the lead researcher on the paper that was published August 8, in the online edition of the journal Nature.