Chipmunk sleeping away the snow flurries.
When out in Western Maryland forests in the winter one can't help but notice that nature seems to be asleep. Just about all plants and many animals take the winter off. They stop growing and they just rest until spring. One of the ways they survive winter is to hibernate.
Hibernation is a state of reduced activity that occurs in some animals during
the winter. In cold weather most animals must eat large quantities of food to
obtain the energy needed to carry on normal body activities. In winter, however,
food often becomes scarce, so many animals cannot survive unless they hibernate.
A hibernating animal greatly reduces normal body activities that expend energy.
It survives on energy reserves, such as fat, stored in the body.
Chipmunk sleeping away the snow flurries.
Mammals that can let their body temperatures drop to just above freezing and can also make their hearts beat very slowly are called true hibernators. A woodchuck can allow its body temperature to drop more than 30 degrees Celsius. When hibernating a mouse that's heart might beat 500 beats a minute will slow to about 30 beats a minute. These animals are known as true hibernators because their normal body functions change dramatically.
Hedgehog a true hibernator.
Some people say a bear hibernates and others do not. Some animals like skunks and raccoons go into a period of dormancy and 'light sleep' and curl up with their kin folk in a den. They still go out and forage sometimes, but mostly just sleep away the winter snuggled up. Their systems and body functions don't change much but they do slow activity way down.
A bear cam of a bear hibernating in her den.
Bears
are masters of winter survival.
During hibernation, an animal lowers its metabolic rate and its body begins to cool instead of maintaining a constant temperature. As body activities slow, the animal becomes less and less capable of coordinated movement, gradually slipping into a state of dormancy, or torpor. If, however, the animal’s body temperature slips below a certain range, the animal will generate heat to boost body temperature to a safe range. Animals may hibernate for several months, but they do not remain completely inactive during this time. Hibernation cycles may last from a few days to a few weeks depending upon the animal, body size, outside temperature, and time of year. Sometimes they wake up to move around and get their body temperature up and then its back to sleep.ZZZZZ
Some boreal (northern) toads can sleep through winter in temperatures of 30 degrees below zero! Their blood has a special substance in it that works like antifreeze. Their burrows may be ice blocked for 8 nine months!
Although hibernation helps animals survive adverse environmental conditions, hibernating animals can still freeze to death, and their lack of mobility and coordination makes them vulnerable to predators. To help protect themselves, many animals hibernate in protected areas, such as caves or underground burrows. These sites often remain several degrees above freezing even when the outside temperature is far colder. Animals usually choose sites that are inaccessible to predators since their defenses are so slowed down.
When animals are hibernating, the changes to heart rate and body temperature are controlled by a part of the brain called the hypothalamus (hi-po-thal-amus). Scientists have discovered that hibernating animals have a special substance in their blood. It is known as H I T, which stands for "Hibernation Inducement Trigger." This substance becomes active when the days become shorter or there is less sunlight. It also becomes active in the late fall when the temperature drops and colder days are more common.
The changes to the body can be very dramatic. To prepare for hibernation, most animals eat large amounts of food in the late summer and fall. They build up layers of fat that keep them warm. The body can also use the fat as a food source during the winter. Most hibernating animals also make changes to their den or home to prepare for winter. They add materials, such as leaves and grasses, to keep them warm. Some animals build special underground rooms for storing food so they don't have to move around too much looking for food.
Hibernation truly is an amazing adaptation and common sense survival tool for wild animals living in our Western Maryland winters. Rather than struggle to dig in snow ands survive on meager food supplies, the great design of nature just says sleep away. Winter really is a time of rest and sleep. Trees and plants do it, animals do it, and maybe we as humans would be pretty happy if we had a few months to curl up, slow down and snooze.