Bats

Bats are nocturnal flying mammals which inhabit dark, secluded places. In western cultures, they traditionally have been associated with witchcraft, sorcery, haunted houses, cemeteries, and evil. For centuries, they have been the subjects of fables, folklore, and myths. Unfortunately, many myths regarding their lives still exist and serve as a basis for unfounded fear. Bats are of medical concern because a very small percentage is infected with rabies, and old droppings may harbor the fungal organism that causes the lung disease histoplasmosis. There are more than 980 species of bats worldwide with about 40 species occurring in the United States. However, none occur in the colder areas located beyond the limit of tree growth.

Recognition.

Depending on the species, adult bats measure about 2 3/16 - 7 1/2" in length from tip of nose to end of tail, with a wingspread of about 6-15", and weigh about 1/8-2 1/8 lbs. for United States species. They are tan to black in color, with very large ears. Bats fly on two wings consisting of a double membrane stretched across enlarged arm bones and elongated finger bones. Their bodies are covered with hair. Bats have two pectoral teats.

Note that bat species are difficult to identify, even by experts. If assistance is needed, contact the wildlife or zoology department of a local museum or university, fish and wildlife personnel, or the local health department.

Habits

The three most common bats to enter structures are the big brown, the little brown, and the Mexican free-tailed bat. All of these bats leave their roosts at dusk and return just before dawn. Usually their first stop is at a stream, pond, or lake for a drink of water, and then feeding begins. Their habits can be summarized as follows:

1. Big brown bat females form nursery colonies in structures in the spring while males roost elsewhere; later in the summer the sexes roost together. They commonly roost in attics and church belfries and behind shutters and loose boards on buildings. They leave their roost about dusk in a slow, fluttering flight. These bats usually feed near the ground on insects, primarily beetles but also wasps, ants, planthoppers, leaf hoppers, flies, moths, etc. They are capable of flight up to 40 mph, the fasted reported speed for any bat. Big brown bats are the most common bat to hibernate in structures in Canada. However, they typically disperse relatively short distances and hibernate singly or in small groups in hollow trees, rock crevices, drainage pipes, caves, mines, and buildings. In Canada, hibernation extends only from December to April.

2. The little brown bats form nursery colonies in structures in the spring. They feed on insects, especially flies and moths. They alternate feeding flights with rest periods during which they hang to digest their catch. Their flight is erratic with flight speed averaging 12.4 mph, but ranging up to 21.7 mph. In the north, most migrate south in the autumn with the migration covering up to 443 miles. From September/October through March/April they hibernate in irregular clusters, using mines and caves in the east. They have good homing instincts as illustrated by a return home in three weeks after being released 270 miles away.