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Indiana Bat
(Myotis sodalis Miller and Allen)

From: Saunders, D. A. 1988. Adirondack Mammals. State University of New York, College of Environmental Science and Forestry. 216pp.

Order: Chiroptera

Family: Vespertilionidae

Description: The fur of the Indiana bat is a dull grayish brown on the upper part of the body, and only slightly paler below. The texture of the fur is fine and fluffy, and each dorsal hair is tricolored: blackish at the base, grayish in the middle, and chestnut brown at the tip. The ears, wing and tail membranes are brownish black. When viewed from below, hibernating individuals display pinkish faces. An average sized adult is 82 mm (3.2 in) in length, weighs approximately 6.5 g (0.2 oz), and has a wingspread of 25.5 cm (10 in).

Range and Habitat: The range of the Indiana bat is a large portion of the eastern U.S., and in configuration resembles an inverted “y”, the main trunk extending from New England south and west, one leg penetrating north central Arkansas, and the other reaching northern Florida. Many populations formerly present with in this area are absent today. This species spends the winter months in caves and mines, including one site in Essex County. This is the only population known to occur in the Adirondack Park. Pregnant females and most males roost in hollow trees or behind loose plates of bark of living and dead trees during summer. Small numbers of males may remain at the winter sites.

The Latin sodalis means companion, and refers to the social habits of hibernating Indiana bats. More than 90% of the total population of 500,000 spend the winter in just five caves or mines in Indiana, Illinois, Kentucky, and Missouri, with two of these locations accounting for more than half the total. Five hibernation site occur in New York. Collectively, they contain 9,000 Indiana bats (the site with in the Adirondack Park has in excess of 500 individuals). Because this species is concentrated during the winter, it is especially vulnerable to disturbance, vandalism, habitat destruction, and natural catastrophes such as flooding.

Food and Feeding Behavior: The few studies of the feeding habits of the Indiana bat suggest it forages at night in the canopy of forests, taking many kinds of insects such as moths, leafhoppers, and beetles. The availability of certain orders of insects in different forest communities, e.g., lowland versus ridge top, determine feeding preferences of local populations. 

Activity and Movement: Indiana bats, some traveling hundreds of miles, assemble at the mouths of caves or mines used as winter shelters in September and October. Males delay their entrance to mate with arriving females. When hibernating, individuals of both sexes alight on the ceiling, hanging head down, and then back into companions, wedging themselves into densely packed clusters. These clusters are usually far back into the recesses of caves or mines where temperatures are usually 3-8 degrees C (37-46 degrees F). Fluctuating temperatures may trigger arousal, with mass movements to different, more ideal locations.

Reproduction: Although mating occurs in autumn, females store sperm until April or May, when ovulation and fertilization take place as they leave winter roosts. Females give birth to a single young in late June or July, and may transport them to different trees to provide warmer roosts. Maturation is weather-related, and cool summers may retard development as much as two weeks. The young begin flying at 25-37 days of age, and they make their first flights by following their mothers when they leave roosts to forage. Some young begin breeding in late autumn of their first year. Longevity is at least 13.5 years for males and 14.8 for females. 

Predators: Unknown.

Social Behavior:

  • Social system - Indiana bats are promiscuous. Pregnant females roost singly or in maternal colonies of 25-100. Males may form small colonies in mines or caves, or roost in small groups in trees during the summer. Males and females are colonial during the winter.
  • Communication - Unknown.

Additional References 

Brack, V., Jr. and R.K. LaVal. 1985. Food habits of the Indiana bat in Missouri. Journal of Mammalogy, 66:308-315.

Clawson, R.L., R.K. LaVal, M.L. LaVal, and W. Claire. 1980. Clustering behavior of hibernating Myotis sodalis in Missouri. Journal of Mammalogy, 61:245-253.

Hicks, A. 1982. Survival of the Indiana Bat. The New York State Conservationist, 36(5):36-37, 39.

Humphrey, S.R., and J.B. Cope. 1977. Survival rate of the endangered Indiana bat, Myotis sodalis. Journal of Mammalogy, 58:32-36.


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