Although it is seemingly quiet these days in the woods around campus and we often think of winter as a dead time, the natural world in our southern mountains never really goes quiet. Few mammals actually hibernate here, really just some bats, since their extremely high metabolism forces them to shut down when their insect prey is unavailable. Bears, squirrels, raccoons, opossums, mice, and even groundhogs may sleep through a cold snap, but they are up and about again during any warm spell. True hibernation in the endotherms (warm-blooded mammals) requires a drastic lowering of the heart rate, respiration, and metabolism and our winters are just too mild and short to call for such measures.
Life is definitely different for the ectotherms whose internal temperature reflect the ambient conditions. These reptile and amphibian species must have some adaptations to cope with those sub-zero days. Snakes are barely functional below 50° F and seek out deep dens (or the barn) to find stable temperatures. The Eagle’s Nest frogs and snapping turtles have burrowed into the mud at the bottom of the pond. One of our few terrestrial frogs, the wood frog, can be frozen solid for months due to antifreeze compounds like propylene glycol and glycerol in their systems. In this torpid state, its breathing and heartbeat actually stop, defying the definition of the word “alive”. Normally, the formation of ice crystals means death for cells, but these frogs have sidestepped that particular fate, with as much as 65% of the water in their bodies crystallized into ice. When warmed, they immediately go about the business of finding mates, none the worse for wear. Not surprisingly, scientists are interested in borrowing this adaptation for the cryopreservation of living human organs for transplant.
Certainly, not all of our summer Appalachian birds leave during the winter. Our feeders are full of chickadees, nuthatches, woodpeckers, and finches. Some of these birds are northern migrants, but many have only migrated down the mountain into our protected Little River valley. They have a short trip back to their breeding territories in the spring. And some birds, like the kestrel, a tiny falcon, come from colder northern habitats to spend their winters hunting here. Even most of the insects aren’t really gone or dead. Many species overwinter as larvae or even as adults and can occasionally be found out and about. Every rock you turn over in the Davidson River in February will be crawling with mayfly, damselfly, stonefly and alderfly larvae. Our yellow jackets colonies, so numerous and feared in the summer, are represented by young queens, the only survivors of the swarms we run from in panic in August. They have been fertilized by males in the late fall and will spend the winter in barn attics or under the bark of a dying tree, ready to start new underground colonies in the spring.
Well, I guess what I’m getting at is that there is always something stirring around here, even in the depths of winter. I’ve heard spring peepers call during every month of the year; Great Horned owls calling for mates in December, fox tracks in the snow, spotted salamanders eggs in March, copperheads sunning in February; groundhogs eating greens in a frosty pasture; and springtails—tiny, hopping insects—leaping on snowy rocks in a frozen river. The natural world doesn’t ever really stop, so don’t let the cold slow you down either – get out there with your binoculars and magnifying glass.