Bat Migration and Hibernation

In winter, when insects are scarce, bats survive by migrating or hibernating. Migrating bats may travel hundreds of miles to warmer temperatures and plentiful insects. Most U.S. bats spend winters hibernating in caves or mines where temperatures are fairly constant. Most bats are very loyal to their hibernation sites and will return year after year, often to the very same spot in the cave. During hibernation bats slowly burn fat that they stored over the summer and fall. Their body temperature drops from about 104°F to the surrounding air temperature of about 40-50°F, and their heart rate drops from 400 beats per minute to less than 25. Bats can lose up to one-half of their body weight during hibernation. Waking a hibernating bat can be deadly for the bat. Frequent disturbances can cause bats to run out of energy before winter is over.

The Canoe Creek site is unique in that the bats' summer and winter habitats are close to one other. The bats spend the winter in an old limestone mine located at the far end of Canoe Creek State Park. The Hartman Mine was abandoned by 1930, but a series of large corridors were left behind. In 1978, shortly after the park bulldozed three large tunnel openings, they were informed of a small population of Indiana bats that hibernated in the mine. In response, some backfill was removed creating a small opening at two entrances. The Pennsylvania Game Commission declared the mine a protected area for Indiana bats in 1985, and special gates were fitted over the entrances. In the end, the limestone mine became the ideal bat hibernation site, providing a variety of microclimates and a lack of disturbance that meets the needs of several species. Today, the mine is the most important hibernation site in Pennsylvania. The largest numbers of little brown and small-footed bats in the state are found here. In all, over 26,000 bats of six different species hibernate in the mine, including 700 endangered Indiana bats.