We know that certain mammals hibernate in the winter. But it turns out, there are a couple of different approaches to hibernation.
Take the black bear. In the early fall, bears pile on the weight, preparing for three to five months of fasting. When they enter their dens, their body temperature drops slightly, and their metabolism slows down. While they are not as deeply asleep as some hibernators, they don’t eat, drink, urinate, or defecate. During hibernation, female bears give birth and nurture cubs.
Eastern chipmunks spend the early fall gathering nuts and seeds that they store in burrows. The tiny animals might store as much as eight pounds of food. Once it gets cold, they enter the burrows, and their body temperature drops to 40 degrees Fahrenheit, much colder than for bears. But periodically, their body temperature rises, and they eat, urinate, and defecate. On warm winter days, they are occasionally seen outside.
Some mammals hibernate automatically when winter arrives, while others wait until the temperature drops or food is scarce. Research has shown that some chipmunks don’t hibernate at all during warmer winters. We need to better understand how future warmer climates will affect these species.
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Web Links
How do chipmunk and black bear hibernation differ? (North American Bear Center)
Photo, taken on February 22, 2007, courtesy of Gilles Gonthier via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY, with partial support from the Field Day Foundation.