Curious Nature: Is winter over yet? Ask a marmot
Vail, CO Colorado
The vernal equinox, or the first day of spring, took place Sunday at 5:21 p.m. Meaning, the sun’s path across the sky crossed the equator, providing the planet with an equal amount of daylight and darkness. Expect more sunlight every day until we reach the summer solstice on June 21. Average temperatures are already greater than they were a month ago and will continue to rise well past the longest day of the year in June.
Sunday officially signified the end of winter but not necessarily for the yellow-bellied marmot, Marmota flaviventris. If you’ve been outdoors in the Vail Valley during summer, then chances are you have heard or seen this animal. Unless you were picking up boulders this winter, you haven’t seen a marmot since October, when they retreated to their burrows under rocks for a six- to eight-month commitment to sleep.
Marmots are textbook hibernators, with the oldest and fattest entering their burrows starting in October. Imagine gaining 30 percent of your body weight from summer to autumn – that’s what this little furball does! The marmot’s weight increases in the form of brown fat stored over most of its body. Brown fat acts like a heat pad for the hibernating animal; it warms the body without any need to shiver.
During hibernation, its heart rate drops from 100 to four beats per minute, respiration rate slows to one breath every few minutes and body temperature falls 50 degrees. This allows the marmot to use very little energy and live off of its fat reserves for the duration of winter. Its metabolism slows so drastically, a marmot falls into a very deep sleep and little will wake it from its slumber. Marmots will wake occasionally during winter (about every two weeks) to defecate. This may occur in special chambers below ground or, less frequently, on the surface. Once the deed is done, they return to their grass beds for more rest.
If the marmot eats enough plant matter in the fall and weather conditions are just right, it will be lucky enough to hibernate through mid-April. If this animal comes out of hibernation too early, it will be vulnerable to predators, have a hard time finding food and waste valuable brown fat reserves needed to sustain it through some more cold days ahead.
Males usually exit a few days earlier than females in late March, April or, sometimes, in May. They will emerge having lost approximately one half their fall body weight. Mating generally occurs within the first two weeks following emergence from hibernation. Young marmots emerge from the natal den in late June and July with weaning occurring in mid-July. So, it’s at least a few more weeks of winter according to the marmot, but after that, keep your eyes peeled for our old friend, especially near talus fields on south-facing slopes.
Brock Nedland is an educator for Walking Mountains. When he’s not out exploring nature with the kids, he enjoys snowboarding or fly fishing in our beautiful surroundings. Would you like to learn more about local critters? Visit the Nature Discovery Center daily at 3 p.m. for free nature tours.
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