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eastern pipistrelle

Pipistrellus subflavus

What do they look like?

Eastern pipistrelles are small bats with yellowish-brown fur. The individual hairs of these bats are tricolored, the base is dark, the middle is yellowish brown, and the tips are dark. This is used to distinguish them from similar species such as western pipistrelles.

In the fall, when these bats have stored fat for hibernation, they weigh around 7.5 grams. In the spring, after they've come out of hibernation, they weigh about 5 grams. Like most bats, female eastern pipstrelles are larger than males. (Farney and Fleharty, 1969; Fugita and Kunz, 1984; Schmidly, 1991; Whitaker and Hamilton, 1998)

  • Sexual Dimorphism
  • female larger
  • Range mass
    4.6 to 7.9 g
    0.16 to 0.28 oz
  • Range length
    77 to 89 mm
    3.03 to 3.50 in
  • Range wingspan
    220 to 250 mm
    8.66 to 9.84 in

Where do they live?

Eastern pipistrelles are found mainly in the eastern United States. They are also found in the far eastern parts of Mexico and Central America. These bats are from Canada in the north, and northern Honduras in the south (Fugita and Kunz, 1984). (Fugita and Kunz, 1984)

What kind of habitat do they need?

Eastern pipistrelles are found in open woods near the edges of water. They often fly over water while hunting. These bats are not usually found in open fields or deep forests (Schmidly, 1991; Nowak, 1991).

Eastern pipistrelles roost in rock crevices, caves, buildings, and tree foliage in the summer. During the winter, they hibernate in caves, mines, and deep crevices (Briggler and Prather, 2003; Sandel et al., 2001). (Briggler and Prather, 2003; Nowak, 1991; Sandel, et al., 2001; Schmidly, 1991; Briggler and Prather, 2003; Nowak, 1991; Sandel, et al., 2001; Schmidly, 1991)

  • Other Habitat Features
  • caves

How do they reproduce?

Eastern pipistrelles mate between August and October while “swarming” in front of cave openings. This is the only time the males and females of this species are together. (Whitaker and Hamilton, 1998)

After they mate, female eastern pipistrelles store sperm while they hibernate. Fertilization and pregnancy occur in the spring (Nowak, 1991). Eastern pipistrelle females usually give birth to twins in late May or early June. Although the young are born hairless, blind, and totally dependent upon their mothers, they weigh up to 52% of the mother's body weight. They develop rapidly, and within several weeks, are able to fly and hunt on their own. Young are able to make a clicking sound to signal their mothers. (Fugita and Kunz, 1984; Hill, 1992; Nowak, 1991; Whitaker, 1998; Wimsatt, 1945)

  • How often does reproduction occur?
    Eastern pipistrelles breed twice a year.
  • Breeding season
    Copulation occurs between August and October and again in the spring.
  • Range number of offspring
    2 to 2
  • Average number of offspring
  • Range gestation period
    44 (high) days
  • Average gestation period
    44 days
  • Range weaning age
    28 (high) days
  • Average weaning age
    28 days
  • Range time to independence
    5 (high) weeks
  • Range age at sexual or reproductive maturity (female)
    3 to 11 months

Female eastern pipistrelles carry their babies to different roosts. Males do not help rear the young. Within one week the young are covered in fur. At 3 weeks they are able to fly. The young are weaned at 4 weeks and begin to forage with their mothers. At 5 weeks the young are independent from their mothers. Juveniles reach sexual maturity within 3 to 11 months. (Fugita and Kunz, 1984; Nowak, 1991; Whitaker, 1998)

  • Parental Investment
  • altricial
  • pre-hatching/birth
    • provisioning
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

How long do they live?

Eastern pipistrelles have a lifespan of 4 to 8 years in the wild (Nowak, 1991). The known record for the oldest P. subflavus is 14.8 years. (Nowak, 1991; Whitaker and Hamilton, 1998)

  • Range lifespan
    Status: wild
    14.8 (high) years
  • Typical lifespan
    Status: wild
    4 to 8 years

How do they behave?

Eastern pipistrelles must hibernate, even if they live in warm climates. They enter their hibernation chamber in late July-October and leave at the beginning of April. They hibernate in the deepest part caves where temperatures are stable all winter. Eastern pipistrelles generally hibernate alone, but groups of 2 or 3 have been observed in Texas caves. This behavior is unusual, since most bats huddle in groups during hibernation. Eastern pipistrelles might choose to hibernate in places near forests and prefer caves with east facing openings.

During the summer, female eastern pipestrelles roost together in groups of about 15 individuals, wheseas males roost alone. Females roost together so that their young can cluster and keep warm while the their mothers are out hunting.

Eastern pipistrelles have short, "fluttery" flight patterns, and are often mistaken for moths.

Like many bats, eastern pipistrelles use sound to navigate and find their food ("echolocation" or "sonar"). They are not blind, but do not have very good vision as compared to their ability to "see" the world by listening to the echoes produced when their calls bounce off of objects. (Briggler and Prather, 2003; Fugita and Kunz, 1984; Patterson and Hardin, 1969; Sandel, et al., 2001; Schmidly, 1991; Whitaker and Hamilton, 1998; Whitaker, 1998)

Home Range

At this time there is no information available regarding the home ranges of P. subflavus.

How do they communicate with each other?

Eastern pipistrelles arevery good at navigating with sound. They produce calls at pitches much higher than the range of human hearing. These calls bounce off of objects as echoes. Based upon the sound and return time of the echoes, the bats can determine the size, shape, position, texture, and movement of nearby objects. Echolocation is a very effective way to hunt for insects and avoid obstacles in the dark of night.

Eastern pipistrelles also produce social calls, which are within the range of human hearing. For example, mothers can identify their young from the sound of their young's call. The young also recognize their mother's call. That's very important when a mother returns to a roost with the young of many other females in it. (Fugita and Kunz, 1984; MacDonald, et al., 1994; Pfalzer and Kusch, 2003; Fugita and Kunz, 1984; MacDonald, et al., 1994; Pfalzer and Kusch, 2003)

Although not specifically mentioned in any references, some communication must occur between a mother and her young through touch. Tactile communication may also occur between mates.

What do they eat?

Eastern pipistrelles eat a variety of insects such as beetles, hoppers, flies and mosquitoes, bees and wasps, moths, lacewings, mayflies, bugs, barklice and caddisflies. Their diet varies geographically.

Becausethey use flight and echolocation, eastern pipistrelles are good hunters. Eastern pipistrelles are able to consume 25% (1.4 g to 1.7 g) of their body weight (5.3 g to 6.7 g) within half an hour. (Carter, et al., 2003; Gould, 1955; Griffith and Gates, 1985; MacDonald, et al., 1994)

  • Animal Foods
  • insects

What eats them and how do they avoid being eaten?

At this time there is no information regarding the natural predators of P. subflavus. Eastern pipistrelles are often killed by humans. Generally, bats are most vulnerable to predators during the day, while they are in their roosts. (Whitaker and Hamilton, 1998)

What roles do they have in the ecosystem?

Eastern pipistrelles are insectivores and help control the populations of the insects they consume.

Do they cause problems?

Eastern pipistrelles sometimes inhabit human dwellings and may be considered un-welcomed guests. (Whitaker, 1998)

  • Ways that these animals might be a problem for humans
  • household pest

How do they interact with us?

Eastern pipistrelles eat many insects that may be harmful to humans.

  • Ways that people benefit from these animals:
  • controls pest population

Are they endangered?

This species is not considered threatened at the global or national levels, but it is a species of special concern in the state of Michigan.

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. (Cryan, 2010; National Park Service, Wildlife Health Center, 2010)


Matthew Wund (editor), University of Michigan-Ann Arbor.

Nancy Shefferly (editor), Animal Diversity Web.

Maria Hamlin (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.


Anthony, H. 1929. Field Book of North American Mammals. London, England: G. P. Putnam and Sons.

Briggler, J., J. Prather. 2003. Seasonal use and selection of caves by the eastern pipistrelle bat (pipistrellus subflavus). American Midland Naturalist, 149: 406-412.

Carter, T., M. Menzel, S. Owen, J. Edwards, J. Menzel. 2003. Food habits of seven species of bats in the allegheny plateau and ridgeand valley of west virginia. Northeastern Naturalist, 10(1): 83-88.

Cryan, P. 2010. "White-nose syndrome threatens the survival of hibernating bats in North America" (On-line). U.S. Geological Survey, Fort Collins Science Center. Accessed September 16, 2010 at

Farney, J., E. Fleharty. 1969. Aspect ratio, loading, wing span, and membrane areas of bats. Journal of Mammalogy, 50: 362-367.

Fugita, M., T. Kunz. 1984. Pipistrellus subflavus. Mammalian Species, 228: 1-6.

Gould, E. 1955. The feeding effeciency of insectivorous bats. Journal of Mammology, 36: 399-407.

Griffith, L., J. Gates. 1985. Food habits of cave-dwelling bats in central appalachians. Journal of Mammology, 66(3): 451-460.

Hall, E., K. Kelson. 1959. The Mammals of North America. New York: The Ronald Press Company.

Hill, J. 1992. Bats: A Natural History. Austin, TX: University of Texas Press.

MacDonald, K., E. Matsui, R. Stevens, M. Fenton. 1994. Echolocation calls and field identification of the easterpipistrelle(pipistrellus subflavus: Chiroptera: vespertilionidae), using ultrasonic bat detectors. Journal of Mammology, 75(2): 462-465.

National Park Service, Wildlife Health Center, 2010. "White-nose syndrome" (On-line). National Park Service, Wildlife Health. Accessed September 16, 2010 at

Nowak, R. 1991. Walker's Mammals of the World, Fifth Edition. Baltimore: The Johns Hopkins University Press.

Patterson, A., J. Hardin. 1969. Flight speeds of five species of vespertilionid bats. Journal of Mammology, 50: 152-153.

Pfalzer, G., J. Kusch. 2003. Structure and variability of bat social calls: implications for specificity and individual recognition. Journal of Zoology, 261 (1): 21-33.

Sandel, J., G. Benatar, K. Burke, C. Walker, t. Lacher. 2001. Use and selection of winter hibernacula by the eastern pipistrelle ( pipistrellus subflavus) in Texas. Journal of Mammology, 82(1): 173-178.

Schmidly, D. 1991. The Bats of Texas. College Station, Texas: Texas A&M University Press.

Tuttle, T., J. Stevenson. 1982. Growth and Surival of Bats. Pp. 105-150 in T Kunz, ed. Ecology of bats. New York: Plenum Press.

Whitaker, J. 1998. Life history and roost switching in six summer colonies of eastern pipistrelles in buildings. Journal of Mammology, 79(2): 651-659.

Whitaker, J., W. Hamilton. 1998. Mammals of the eastern United States. Ithica, NY: Comstock Pub. Associates.

Wimsatt, W. 1945. Notes on breeding behavior, pregnancy, and parturition in some vespertilionid bats of the eastern United States. Journal of Mammology, 26: 23-33.

University of Michigan Museum of ZoologyNational Science Foundation

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Hamlin, M. 2004. "Pipistrellus subflavus" (On-line), Animal Diversity Web. Accessed April 12, 2024 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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