Solving Problems with Nature - Naturally
ERIC P. ORFF
Certified Wildlife Biologist
Wildlife Author - Wildlife Lecturer -
Non-Lethal Control of Bats since 1983
New Hampshire’s Hibernators
By Eric Orff
Yawnnnnnnnnnnnn. Down, down into my winter burrow you will find me soundly asleep in my winter woodchuck world. Wouldn't you like to sleep in on these snowy winter mornings, like I do? In fact, I'll sleep five months if I must, to avoid this wicked winter. I've chosen a nice grove of oaks to build my winter burrow in, not far from the cool summer burrow where I raised my three little ones (lest a hungry coyote nab me in my fat waddly search for my new home). No trips to the gym for me, but still I'll wake up next March or April about half the weight I was when I waddled into my winter sleep chamber. Oh, it's so cozy down here. I'll let my body temperature cool from 104 degrees F to maybe 38 degrees. I'm so relaxed, that my heartbeat slows down 95 percent (!), from 105 beats per minute to just 4. Four sloooooooow beats. Very,very relaxed. So, so sleepy. Yawnnnnnnnnnnnnnnnn.
Seven types of mammals dodge the depths of New Hampshire's winter by snoozing it away. Bats, woodchucks, chipmunks and jumping mice go into a deep sleep, or hibernation. For these animals, life nearly ceases; they are at death's door. Yet, somehow, an alarm clock built into their bodies awakens them at just the right time. Imagine if you could hit the snooze button for four more months! Not only do these animals get to sleep as long as the average teenager, they actually have a weight loss program that works -- the winter sleepers lose between 25 and 50 percent of their weight while sleeping. Rounding out the seven sleepers, bears, raccoons and striped skunks sleep during the cold months, but not as deeply as the true hibernators. Sometimes they snooze only during the coldest, snowiest parts of the winter.
*WOODCHUCKS are masters of winter sleep. By late September, when air temperatures drop into the 40s, woodchucks go into hibernation. The woodchuck's weight will drop by about half over the winter. Its heart rate plummets from 105 beats per minute to just 4, and body temperature drops from 104 degrees F to about 38.
*BATS are also true hibernators. By late August or September, five species of New Hampshire bats are headed for their winter dens. These are usually caves or mines, not necessarily in this state, but possibly as far as 200 miles away. The last days of summer were spent adding about 25 percent to their body weight in order to have enough fat to last the seven months in hibernation. Bats' heartbeat slows from 210 per minute to just 8. A bat's body temperature may drop from nearly 100 degrees F to 32. Shivering prevents their body temperature from dropping below freezing.
*JUMPING MICE, both woodland and meadow, occur across the state and, like bats and woodchucks, are true hibernators. They curl into a little ball and sleep for two or three weeks at a stretch, briefly awaken, then resume their torpor. Their body temperature hovers just above freezing.
*CHIPMUNKS are winter wanderers between weeks-long periods of sleep. These little creatures take the time in late fall to store a cache of winter food which they eat during waking periods over the winter. Typically, chipmunks have excavated one or two chambers in their underground burrows and have filled them with hundreds of nuts. They, too, are true hibernators, as their body temperature drops from 96 to 106 degrees F to as low as 42-45 degrees F. Their heart rate slips from 60 per minute to 20. A mild winter day with little snow and an abundance of acorns will draw chipmunks out of the den for a winter scamper.
*BEARS may double their weight in late fall in preparation for denning. Autumns with a lack of nuts and other foods, as we experienced in New Hampshire in 2003, can send some bears into their dens as early as September. During falls with an abundance of nuts, especially beechnuts or acorns, bears often will stay active into December. Bears usually build a den on top of the ground or under a blow-down or brush pile. Their winter sleep is not as deep as that of the true hibernators, as bears remain alert and can run away or defend themselves if disturbed. Their body temperature drops only about 10 degrees, from 100 degrees F to 90. Respiration drops more significantly, from about 40 to 8-10 breaths a minute. Unlike chipmunks, bears do not eat or drink or even relieve themselves during the 5-6 months of denning. Yet, adult female bears give birth to two or three cubs in January about every other year. They are able to nurse the cubs and care for them during the coldest of months by relying on body fat stored from the previous fall.
*RACOONS AND STRIPED SKUNKS are the last of the winter sleepers. Unlike the true hibernators, these animals may sleep only during the coldest temperatures and the deepest snows, but remain active periodically throughout the year. There is no dramatic reduction in their body temperatures, heart rate or respiration. Life goes on, just at a slower pace. Just like us humans! To conserve energy, both raccoons and skunks congregate in communal dens. Often, it will be the mother and her young from the summer who will den together, but sometimes as many as 12 to 20 raccoons may den together. Skunks enjoy mixed company of other skunks, as well; there can be 20 or more in a den, but usually no more than 10. Skunks, especially females, prefer to make their winter dens under or in buildings. Have you noticed a telltale odor of skunk this winter? If you have, get ready for the blast of reality when skunk-breeding season rolls around in January! Male skunks may travel over two miles a night in search of that den full of vivacious babes. Squabbling males or reluctant females may cause a stir that will include some spraying. Keep that clothespin handy! The denned skunks tend to have two or three brief active periods each day, each lasting less than 10 minutes. Skunks have a slight depression in body temperature and lose between 40 and 58 percent of their body weight. New Hampshire's seven sleepers are all snuggled into their dens for a long winter's nap. Wouldn't it be nice to sleep through that next big snowstorm, or, better yet, that ice storm when the power is out? Plus, great news - "you snooze, you lose." If Christmas dinner, ribbon candy and holiday parties have you putting on a few extra pounds, remember, the solution is only a nap away