for National Geographic News
When researchers at the Rocky Mountain Biological Lab in Crested Butte, Colorado, started documenting marmot hibernation patterns in the 1970s, the animals rarely awoke before the third week of May.
But these days, the scientists say, marmots regularly end their winter naps a month beforehand—by the third week of April.
These abbreviated hibernations are part of a growing body of evidence suggesting that hibernating animals are waking up earlier—or not going to sleep at all—due to rising temperatures from global warming.
From chipmunks and squirrels in the Rocky Mountains to brown bears in Spain, these altered slumber patterns are putting animals at risk both of starvation and increased predation, researchers say—which could bring many species to the brink of extinction.
"With respect to the marmots, at least, the evidence is convincing that it is connected to warming temperatures," said David Inouye, a biology professor at the University of Maryland who collaborated with the Rocky Mountain Biological Lab researchers.
Average low temperatures in April in Gothic, Colorado, the site of the marmot study, have climbed 2.5 degrees Fahrenheit (1.4 degrees Celsius) since 1976, the first year researchers began recording marmot hibernation stats. (Get a global warming overview.)
(Related: "Warming Sign? Another Early Spring for Rocky Mountains" [April 9, 2007].)
Sending the Wrong Signals
Scientists say it's logical to believe that rising springtime temperatures explain why animals are awakening at times that they would normally be snoozing.
Hibernating animals survive on fat reserves during the winter months when food is scarce. During hibernation, their metabolisms slow and their body temperatures drop to levels close to ambient air temperature.
As long is the air is cold, the animals' bodies are too, consuming very little of the fat they accumulated in summer and fall.
But as air temperature increases, so does body temperature and metabolism. The animals begin to use their stored fat more quickly, sending the signal that it's time to wake up and look for something to eat.
SOURCES AND RELATED WEB SITES