Marmots in Colorado Fatter, More Populous, Due to Climate Change

(July 21) -- Some squirrels are getting a lot plumper than they used to be, but the root cause of their weight gain isn't what you might suspect (not saturated-fatty nuts, sorry!): It's global warming.

That's the conclusion drawn in a three-decade-long study on the yellow-bellied marmots -- large ground squirrels also known as rock chucks -- that inhabit the Upper East River Valley in Colorado, the results of which are in the latest issue of the journal Nature. It's reportedly the first time that climate change has been linked to physical changes in an animal population.

Longer summers are causing marmots -- which are large, ground-dwelling squirrels -- to become heftier, heartier and more plentiful, according to a 33-year study published in the latest issue of Nature.

A yellow-bellied marmot is shown at the Mount Evans Scenic Area in Colorado in 2007.

The study's authors -- researchers from the U.S. and the U.K. -- observed that as the summers in their 2-mile-high territory in the Rockies got longer over time, the marmots became heavier by about a pound. But...why?

"The researchers found that marmots are waking up from hibernation around 21 days earlier now," Discovery News explains. Less time hibernating means more time spent scrounging for and consuming food -- which can include grains, fruit and bugs. In addition, as an article accompanying the Nature story notes: "The marmots may, for example, have changed what they eat, not just the length of time in which they eat."

The longer summers also mean more time for love: The population of marmots has tripled in the last decade alone, passing their heft onto their offspring, which in turn have more time to grow even larger thanks to the shorter hibernation period.

Ironically, unlike humans, fatter marmots are actually fitter too: The team found that the marmots' mortality rate had declined substantially over the period of the study. However, before you start to worry about "super marmots" reproducing out of control and taking over the world, remember that the grand global warming experiment continues and the end result is far from certain.

"Will populations thrive in the changing climate? We suspect that this population increase is a short-term response," said lead author Arpat Ozgul, of Imperial College London, according to the AFP.

Co-author Dan Blumstein, of the University of California-Los Angeles, was even more pessimistic, according to LiveScience.

"Snow patterns both benefit and harm marmots," Blumstein said. "Prolonged snow cover in the spring increases mortality and reduces reproduction. But if there's less snow melt to nourish plants that marmots forage in the summer, it will severely affect them. In droughts, we've had very high mortality."

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