Activity requires energy, and energy requires a food source in the animal kingdom. As warm-blooded mammals, bats are forced to follow these basic biological guidelines, and that is precisely why bats — like the Big Brown bats that take up residence in attics throughout Ohio every winter — enter hibernation (or more accurately, torpor) every year. Understanding the facts behind this particular bat behavior can provide considerable peace-of-mind to bewildered home owners unexpectedly discovering bats in living rooms, bedrooms and other living spaces throughout the home in the depths of winter.
Let’s begin with why bats hibernate. It starts with a bat’s diet. Big Brown bats feast for three seasons by using echolocation to locate airborne insects. The arrival of cold weather heralds the disappearance of flying bugs, removing the food source vital to maintaining a bat’s active metabolism. When these vital resources disappear, bats must find alternatives to assist them in maintaining a minimal body temperature that prevents freezing to death in the middle of winter. There are many suitable natural options available, along with some man-made shelters — like your home.
Human homes provide ideal shelter for bats. Hidden in attics, nestled between walls and settled comfortably in other nooks and crannies, bats can survive the winter without expending valuable energy. That’s because bats require specific temperatures for hibernation ranging from 35 to 40 degrees Fahrenheit. Big Brown bats have discovered these locations provide that perfect temperature range for survival, and have adapted to hibernating in these man-made locations rather than caves.
If the winter residence is too warm, bats expend too much energy and face starvation. Should the temperature inside the bat’s shelter fall too far, then the bat colony will freeze. Usually, this means that the bats will gather together under insulation, to get near the warm side of a ceiling or wall. (This behavior also explains why you will rarely see bats hanging upside down in an attic in the middle of winter. It’s just too cold for survival.)
Homeowners with a colony of bats in their home often describe a “scratching” noise coming from the ceiling or walls. It’s suspected that these sounds are made when bats adjust the position inside your home in connection to internal and external temperatures.