It’s autumn, and whether you’re a bird or a bat, you may be on the move, heading south for the winter. While many of us are aware of bird migrations during the spring and fall, few of us realize that bats migrate as well. As with birds, some bat species “disperse” short distances, as little as 10 or 20 miles, others “migrate regionally,” hundreds of miles between summer and winter roosts, and a few species “migrate long distances,” typically from Canada and the New England states down to the southern United States.
Whether you migrate regionally or over a long distance, migration is a costly venture and there needs to be a good reason to pack your bags for a long fall trip. With bats there are two reasons why you would migrate. First, you need to remember that the majority of our North American bats are insect eaters and once winter rolls around their food source is gone. This is why many bat species have opted to hibernate (short distant dispersals or regional migrants) as opposed to migrating long-distances. Second, winter temperatures can be harsh and physiologically stressful even if you can find food, limiting your chances of survival.
Virginia’s state bat, the Virginia big-eared bat, disperses short distances between warmer caves used during the summer as maternity or bachelor sites, to colder caves used to hibernate. Other species such as the little brown, Indiana, and tri-colored bats move longer distances, often over 100 miles between summer tree roosts and caves used for hibernating. The long distance migrants found in Virginia include the red, hoary, and silver-haired bats. These are bats that use trees as roost year round and are often found migrating through Virginia on their way north or south in the spring or fall.