Pipistrellus subflavuseastern pipistrelle

Geographic Range

Eastern pipistrelles, Pipistrellus subflavus are found throughout the eastern United States, and the far eastern edge of Mexico and Central America. These bats are found as far north as the southern edge of Canada and the southern edge of their range ends in northern Honduras (Fugita and Kunz, 1984). (Fugita and Kunz, 1984)


Eastern pipistrelles can be found in open woods near the edges of water, as well as over water. They are not usually found in open fields or deep forests (Schmidly, 1991; Nowak, 1991). They roost in rock crevices, caves, buildings, and tree foliage in the summer. During the winter, caves, mines, and deep crevices serve as hibernacula (Briggler and Prather, 2003; Sandel et al., 2001). (Briggler and Prather, 2003; Nowak, 1991; Sandel, et al., 2001; Schmidly, 1991)

  • Other Habitat Features
  • caves

Physical Description

Eastern pipistrelles are small bats with yellowish-brown pelage. The individual hairs of P. subflavus are tricolored; the base is dark, the middle is yellowish brown, and the tips are dark. This trait may be used to distinguish them from similar species such as Pipistrellus hesparus.

The tragus of P. subflavus is long, straight, and bluntly rounded. The calcar lacks a keel, the membrane is blackish, and the dorsal base of the interfemoral membrane is furred (Schmidly, 1991). Eastern pipistrelles have a dental formula of I 2/3, C 1/1, P 2/3, M 3/3 = 36 (Whitaker and Hamilton, 1998).

Eastern pipstrelles are sexually dimorphic: Females are larger than males. In the fall, the mean weights of females and males are 7.9 g and 7.5 g, respectively. In the spring, females average 5.8 g, and males average 4.6 g.

The measurements for P. subflavus are as follows: length 77 mm to 89 mm; tail 34 mm to 41 mm; hind foot 7.3 mm to 9.9 mm; ear 12.4 mm to 14.1mm; forearm 31.4 mm to 34.1 mm; and wingspan 220 mm to 250 mm (Fugita, and Kunz, 1984; Farney and Fleharty 1969). (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


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

After copulation, female eastern pipistrelles store sperm over hibernation until they ovulate in the spring. Insemination occurs in the spring with ovulation (Nowak, 1991). Up to seven ova may be fertilized, but only two will implant. This results in twins (Wimsatt, 1945). Newborn twins weigh up to 52% of the weight of the mother. It has been suggested that having twins is a response to the high mortality rate of the young, however having twins is rare among bats (Hill and Smith, 1984).

Gestation lasts 44 days from the time of implantation to parturition. Birth occurs from the end of May to early June depending on the latitude of the population (Whitaker, 1998). The young are altricial, however they are able to make a clicking sound to signal their mothers (Fujigta and Kunz, 1984). (Fugita and Kunz, 1984; Hill, 1992; Nowak, 1991; Whitaker, 1998; Wimsatt, 1945)

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

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


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


Eastern pipistrelles are obligate hibernators, in warmer climates they hibernate even though food is available (Briggler and Prather, 2003). They enter the hibernaculum in late July-October and leave at the beginning of April (Fugita and Kunz, 1984). They hibernate in the deepest part of the hibernaculum where temperatures are stable (Schmidly, 1991). Eastern pipistrelles generally hibernate individually, but groups of 2 or 3 have been observed in Texas caves (Sandel et al 2001). This is in contrast to other populations of bats which huddle during hibernation. Eastern pipistrelles might choose hibercula based on the closeness to and abundance of forests available to them (Sandel et al, 2001). They also prefer hibernacula with east-facing openings (Briggler and Prather, 2003).

During the summer, female P. subflavus roost in maternity colonies with an average of 15 individuals. Males roost alone (Whitaker, 1998).

Eastern pipistrelles are sporadic flyers with a short elliptical flight pattern (Patterson and Hardin, 1969). They are often confused for moths (Whitaker and Hamilton, 1998) (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.

Communication and Perception

Eastern pipistrelles are effective echolocators. Their echolocation calls are a combination of fundamental and second ary harmonics, which helps to distinguish their calls from those of similar species which share their geographic range. The use of harmonics allows eastern pipistrelles to increase their target resolution and aids in their ability to efficiently capture prey (MacDonald et. al., 1994).

The young are able to call to their mothers (Fugita and Kunz, 1984). These calls are a type of social call that signals female-infant interactions. These calls allow mutual recognition (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.

Food Habits

Eastern pipistrelles are insectivores and are considered generalists. Stomach content and fecal analysis show that eastern pipistrelles consume a variety of insects including Coleoptera, Homoptera, Diptera, Hymenoptera, Lepidoptera, Neuroptera, Ephemoptera, Hemiptera, Psocoptera and Trichoptera. The diet of pipistrelles varies geographically (Griffith and Gates, 1985; Carter et al., 2003).

Because of their effective use of harmonics during echolocation, P. subflavus is an efficient hunter (MacDonald et al., 1994). 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 (Gould, 1955). (Carter, et al., 2003; Gould, 1955; Griffith and Gates, 1985; MacDonald, et al., 1994)

  • Animal Foods
  • insects


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)

Ecosystem Roles

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

Economic Importance for Humans: Positive

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

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

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

  • Negative Impacts
  • household pest

Conservation Status

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.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map


uses sound to communicate


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


uses smells or other chemicals to communicate


used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.


The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.


An animal that eats mainly insects or spiders.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


marshes are wetland areas often dominated by grasses and reeds.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


uses sound above the range of human hearing for either navigation or communication or both


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


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 http://www.fort.usgs.gov/WNS/.

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

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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 http://www.nature.nps.gov/biology/wildlifehealth/White_Nose_Syndrome.cfm.

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.