Pennsylvania Field Office
Northeast Region

Indiana Bat
Life History and Biology

Indiana bat Myotis sodalis

STATUS: Endangered

DESCRIPTION: The Indiana is a small bat about the size of a mouse. They are a dull grayish chestnut color.

Bats mate in fall before entering caves for hibernation. Females store sperm through winter and become pregnant in spring after hibernation, then migrate to summer areas, where they roost under peeling bark of dead or dying trees to have their young (called pups). These bats have only 1 pup each year.

RANGE AND POPULATION LEVEL: The Indiana Bat is found over most of the eastern half of the US. However, most large hibernating populations are found in Indiana, Missouri and Kentucky.

HABITAT: Indiana bats hibernate during winter in caves and abandoned mines. Suitable hibernation sites in caves must be draft- free and have a constant winter temperature. After hibernation, Indiana bats migrate to summer roosts, which are generally edges of hardwood forests. During summer, males roost singly or in small groups. Females may roost in groups of up to 100 bats.

REASONS FOR CURRENT STATUS: Indiana Bat populations have been declining since early 1960s. The declining numbers were observed at hibernation sites such as caves and abandoned mines, where the bats gather in large numbers. There are several scientific theories as to what factors are contributing to the bats' decline:

  • 1. Human Disturbance - First listed as endangered largely because of their habit of living in very large numbers in only a few caves. This makes the bats extremely vulnerable to disturbance. Significant portion of the population can be affected by just one event.
  • 2. Cave Commercialization and Improper Gating - Any gate or structure placed on the cave or mine that prevents bat access or alters air flow, temperature, humidity, or amount of light is harmful.
  • 3. Low Birth Rate - Because of low reproductive rates (Indiana Bats typically have only 1 young each year) coupled with a potentially high death rate, it may take years to replace lost individuals.

Fact Sheet
Indiana Bat Conservation Guidance (pdf 103KB)
5 Year Review
(pdf 800KB)
USFWS White-Nose Syndrome Web Site
White-Nose Syndrome – Pennsylvania Game Commission Web Page
Report Sick or Dead Bats
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Species Information
Last updated: November 30, 2012
All images by FWS unless otherwise noted.