Bats in Illinois are insectivores, and when temperatures drop, food can become sparse. Different bat species survive the winter in different ways. Some bats, like the Hoary Bat and Red Bat can migrate long distances to warmer places where they may remain active or hibernate. Others like Little Brown Bat may migrate long distances to a hibernacula.
Big Brown Bats spend their winter in caves, mines, houses, and other buildings. As the most cold tolerant species, they don’t travel far from their summer homes in trees, bridges, caves, houses, and other buildings.
Bats can enter a state of torpor – lowering their body temperature, slowing body functions, and remaining inactive to conserve energy. Torpor can last as little as a few hours to get through a cold day to as much as a month or more to get through the winter.
When bats are hibernating, they alternate between torpor for an extended period and awake for a short period.
The Silver-haired Bat varies its winter strategy with some migrating south to Mexico and others overwintering in the northern part of their range. In Illinois, many overwinter along Lake Michigan.
Read more about their overwintering strategies
Return to Migration
Return to Bats