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Pipistrellus sublfavus - Eastern Pipistrelle

Geographic Range (WI):

Pipistrellus subflavus is found throughout most of the eastern United States. It ranges from southeastern Minnesota south to Texas and eastward. This bat species is found locally in western Wisconsin (Whitaker 1996, Yahooligans 2003 and Veilleaux, Whitaker and Vielleux 2003).

Physical Characteristics:

Length is approximately 2 inches. Hair is tri-colored: dark near skin, lighter in the mid-region and dark at the tip. Color ranges from reddish to light brown. Belly light. The Eastern Pipistrelle has a keeled calcar and has a tiny premolar behind it’s canine tooth. This is unusual because most other bat species have two. Body length ranges from 3 1/8 – 3 1/2 inches with the tail length making up approximately 1 3/8  – 1 3/4 inches of the total measurement (Whitaker 1996, Macdonald 1999 and Alien Earth 2003).

Natural History:

Food Habits-

The Eastern Pipistrelle is insectivorous feeding mainly on small insects such as leafhoppers, moths, flies and beetles. This bat exhibits an interesting flight pattern that mimics moths. It flies slowly and flutters unevenly while catching insects along streams, lakes and ponds near wooded areas. It is believed this unusual flight helps the bat when hunting for food. Pipistrelles will die if they are without food for more than 3 days (Whitaker 1996, “Pressure” 1996 and Alien Earth 2003).


The Eastern Pipistrelle is unique among bats in that females usually have twins. It is estimated that gestation lasts approximately 44 days. It is possible for females to store sperm during hibernation. They can delay ovulation until hibernation is over. Young feed on mother’s milk. Females and young form maternity colonies of approximately 30-35 individuals.  These colonies are sometimes found in buildings, but are most often in hollow trees. Young are altricial, taking approximately one year to reach sexual maturity. For young bats, the first few weeks are most critical. Since they are unable to fly at this age, it is common for them to fall to the floor of their hibernacula and become food for other creatures. This bat mates in the fall (Alien Earth 2003, BAT Conservation of Wisconsin 2001, Yahooligans! 2003, Whitaker 1996).


In warmer months the bats hang among leaves, in crevices of buildings or hollows of trees. The Eastern Pipistrelle hibernates more in caves than any other eastern bat species. These bats are very susceptible to cold and for that reason are usually the first to begin hibernation and the last to emerge from it. Hibernation usually occurs in caves or cave-like areas. During hibernation Eastern Pipistrelles are over covered with frozen water droplets which gives them a crystalline appearance (“Pressure” 1996, Whitaker 1996, Alien Earth 2003 and BAT Conservation of Wisconsin 2001).


Eastern Pipistrelles are a primarily woodland species found in eastern forests. This stands to reason since they spend days hanging among leafy tree branches and sometimes form maternity colonies in tree hollows. These bats are found around ponds and streams near forest edges where insects are present, although it is not uncommon to find Eastern Pipistrelles roosting in caves and buildings (Davis and Mumford 1962, Kurta and Teramino 1994 and Veilleux, Whitaker and Veilleux 2003).

Impacts of Eastern Pipistrelles on Humans:


These bats help to control insect populations. It is not uncommon for these bats to eat thousands of insects per night (BAT Conservation of Wisconsin 2001).


Some people find bats in general to be somewhat of a nuisance. Bats sometime nest in homes, which causes some aggravation. People have concerns about bats getting caught in their hair and others worry about catching rabies. While bats can carry this disease, it is very rare that a human being would catch it through normal interaction (BAT Conservation of Wisconsin 2001).


The Eastern Pipistrelle derives it’s name from the latin word “pipilo” meaning to squeak or chatter (Peterson 1964).

In recent research it has been observed that Eastern Pipistrelles only leave their caves to hunt when there is a large quantity of insects to feed upon. On nights when insect counts are low, the bats tend to stay put. It’s been suggested that these bats can sense changes in air pressure and use this information to predict the behavior of their prey. The bats use the Vitali organ (the same way as migrating birds) to detect pressure changes. Another possible use for this system is to regulate their metabolism (“Pressure” 1996).

Eastern Pipistrelles are the smallest bats in the eastern United States (Whitaker 1996).

The Eastern Pipistrelle is more likely to be killed by predators like weasels, owls, raccoons, skunks, hawks and snakes than any other North American bat (Alien Earth 2003).

There are four subspecies of Pipistrellus subflavus: clarus, obscurus, subflavus and veracrucus. It is Pipistrellus subflavus obscurus that makes its home in Wisconsin (Hall and Kelson 1959).

Bats, in general, are unusual among mammals because the young are born feet first (Alien Earth 2003).

Bats are the only mammals that exhibit true flight. This is due to a modification of their forearms into wings. In fact, their ordinal name Chiroptera means “hand-winged” (DeBlase 1981).

In China bats are considered good luck and are welcome guests in homes (BAT Conservation of Wisconsin 2001).

Literature Cited:

Alien Earth/Three Teachers Software. 2003. “Bats: Eastern Pipistrelle.”  <>.  Accessed November 12, 2003.

BAT Conservation of Wisconsin Inc. 2001. “Bats of Wisconsin.”  <>.  Accessed November, 12 2003.

Davis, W., and R. Mumford. 1962. Ecological Notes on the Bat Pipistrellus subflavus. American Midland Naturalist 68(2)394-398.

DeBlase, A., The Manual of Mammalogy. 1981. p.145

Kurta, A., and J. Teramino. 1994. A Novel Hibernaculum and Noteworthy Records of the Indiana Bat and Eastern Pipistrelle (Chiroptera: Vespertillionidae). American Midland Naturalist. 132(2)410-413.

Hall, E.R., and K. Kelson. Mammals of North America Volume 1. 1959. p.183.

Macdonald, D. (ed.), The Encyclopedia of Mammals. 1999. pp. 796-817.

Peterson, R., Silently, By Night. 1964. p.23.

“Pressure in the Bat Cave”, Discover, Vol. 17 No.3, March 1996.

Veilleux, J.P., J. Whitaker, and S. Veilleux. 2003. Tree Roosting Ecology of Reproductive Female Eastern Pipistrelles, Pipistrellus subflavus, in Indiana. Journal of Mammalogy. 84(3)1068-1075.

Whitaker, J., 1996. National Audubon Society: Field Guide to North American Mammals. pp. 347-348.

Yahooligans! 2003. “Mammals: Eastern Pipistrelle.”  <>.

Reference written by Kelli Briski, Biol 378: Edited by Chris Yahnke.
Page last updated 4-29-04.

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