What Bats Look Like
A very common species that roost in houses are the big brown and the little brown bat. They both roost in buildings, and the big brown bat will occasionally fly during warm winter spells and make sudden appearances in a house.
Bats are our only true flying mammal. Bats are warm-blooded, furry, and they nurse their young. They are not blind. The little brown bat (Myotis lucifugus) is a brown, mouse-sized creature. The big brown bat (Eptesicus fuscus) is perhaps twice the size of the little brown bat. It weighs only a half-ounce.
Bats’s Living Habits
Bats roost in caves, under loose bark of trees, under bridges, and in other protected places in the wild. Unfortunately, since the natural habitat is constantly getting smaller, bats will seek cover in attics, behind chimneys, under eaves, between walls, behind shutters, in ceilings, and under shingles.
Bats in North America primarily feed on insects. Common food includes mayflies, moths, midges, mosquitoes, caddis flies, beetles, and flying ants. They can consume large quantities of insects, with some eating up to one-third their body weight in one hour. They are often attracted to insects around swimming pools, ponds or white lights.
Bats use ultrasound, or high frequency sounds like a dog whistle, to locate prey and avoid obstacles. They also emit audible sounds to communicate with each other. They usually leave their roosts to feed between 1/2 hour before and 1/2 hour after sunset, usually on calm days. They return during the night to rest, leave again before dawn and return to sleep during the day. Around the time of the first frost, bats prepare for the winter hibernation. Many bat species will migrate south for the winter.