How
animals survive
By Bruce Auchly MONTANA FISH, WILDLIFE AND PARKS
Animals of
Montana have long prepared for winter. Those still here, that is those that did
not migrate, are either asleep or hunkering down for the long winter.
Asleep means
hibernation, both real—think marmots and bats—and those that simply enter a
deep sleep but technically do not hibernate, bears for example. True
hibernators lower their body temperature and respiration rates. Bears, while
not truly hibernating, are curled up, insulated by fur, fat and snow depth from
the ravages of winter. They can and occasionally do wake up briefly, but they
will generally sleep for months.
Deer, elk
and antelope stay awake and survive winter through four main adaptations: an
insulated coat, reducing their metabolism by as much as one-third of what they
need to meet basic life functions, remaining bedded for long periods during bad
weather and relying on stored body fat.
Up to 30
percent of a deer’s winter energy requirements can be met through body fat. By
the way, don’t believe the old hunter’s tale of predicting a winter’s severity
by the amount of body fat on a deer or elk. The amount of fat says more about
the animal’s ability to find adequate food in the late summer and fall than the
upcoming winter.
Birds that
survive a Montana winter require special equipment. Waterfowl, like geese and
ducks, will stand or sit for hours on an ice shelf next to a river’s open water
to better see and escape predators. They survive by wearing a nice, plump down
coat. Their exposed feet have adapted, too.
First, their
legs and feet have very little muscular, or soft, tissue that needs blood to
keep warm. The few muscles that operate the foot are mostly higher up in the
feather-covered leg and connected to the bones of the feet with long tendons.
Second, warm
blood flowing through the birds’ arteries passes close to cold venous blood
returning from the feet. As arterial blood warms up the venous blood the few
tissues in the feet receive just enough warmth to avoid frostbite.
All birds
have feathers that create air pockets between the feathers and the skin that
help contain heat. And many have behavioral techniques to survive. Some cluster
together. Others will roost in tree cavities, dense foliage or brush piles to
cut both the wind and heat loss. Grouse will bury themselves in snow. Depending
on the species, some birds can even shiver specific muscles to increase
metabolism and generate extra heat.
Animals that
spend their winters in Montana have evolved some amazing strategies to survive.
We should be so lucky.
