A bat maternity colony is a temporary association that pregnant or nursing bats create for giving birth, nursing, and weaning their young ones. The colony breaks up after the bats have weaned their young, and the juveniles have flown away. Its size varies from fewer than ten individuals to as many as over 15 million bats.

Some benefits of a bat maternity colony to the bats include:

• Maintaining constant body temperature by sharing body heat.
• The strength of numbers; bats are small animals, but a large number of bats in a single colony can ward off predators.
• If a bat dies, another bat can foster her pup until it is mature enough to fend for itself.

Bats choose safe, warm, and dark places like caves, abandoned mine shafts, trees, abandoned buildings, or human houses to roost and create colonies. They hibernate during the winter and mate within the summer. Bats begin their maternity season in the summer after the males and females mate.

After mating, the females change their behavior and relocate to a place where they can safely give birth to their young.