Some Like It Warm (If They’re Marmots)
Warmer temperatures in the Colorado Rockies have produced a population boom of yellow-bellied marmots, at least in one well-studied valley. In an unusual,
long-term study, scientists have been tracking marmots there since 1962. A new paper compares marmots from 1976 through 2008 to look for the effects of
global warming on the animals.
Over that time, the winter thaws have been arriving sooner, and the marmots have been emerging out of hibernation earlier — the first sighting of a marmot
now comes around April 20, a month earlier than in 1976. They have also been going back into hibernation later in the fall.
That gives them more time to eat and grow, and the result is that a female marmot was on average about 7.6 poundsduring the second half of the observational
period, about three-quarters of a pound more than the average in earlier years, researchers reported in the current issue of the journal Nature.
Until 2000, the population remained steady at about 100. But as the marmots got heavier and the winters shorter the percentage surviving winter hibernation
rose to 80 percent from 70 percent. The population has since tripled.
The data on the marmots give some hints of how different species might react to a changing environment. (By contrast, scientists reported last year that
warmer winters on a Scottish isle led to smaller sheep, because smaller lambs that would have starved to death in the past now survive.)
And although marmots in the valley, which now number 300, are thriving today, continued global warming may not be such good news, the researchers warned,
because of the increased chance of summer droughts.
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