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Tri-colored bat

The eastern pipistrelle is the smallest of the Adirondack bats. Adults weigh 4-8 g (0.1-0.3 oz), have a total length of 77-89 mm (3.0-3.5 in), and a wingspan of 21-26 cm (8-10 in).  Females are heavier than males, but both sexes are colored alike - yellowish, reddish or pinkish brown above, and a paler yellowish or yellowish orange below. The dorsal hairs are grey at the base, yellowish brown in the middle, and tipped with brown. The black wing membranes contrast with the pink forelimbs. The thin, pinkish tan ears are longer than broad.

(Perimyotis subflavus)

in Saunders refered to as Eastern Pipistrelle - Pipistrellus subflavus F. Cuvier From: Saunders, D. A. 1988. Adirondack Mammals. State University of New York, College of Environmental Science and Forestry. 216pp.

Order: Chiroptera
Family: Vespertilionidae

Range and Habitat

The forested areas of most of extreme south eastern Canada, the eastern U.S., Mexico, and Central America comprise the range of the eastern pipistrelle. Although information on the breeding locations and elevational range of this species is scant for the Adirondack Park, its presence in winter among caves and mines in the region suggests the eastern pipstrelle is a widespread species. Buildings, tree cavities and foliage, rock crevices as well as caves and mines, provide summer roosts.

Food and Feeding Behavior

Eastern pipstrelles begin foraging early in the evening, and take small flying insects (leafhoppers, beetles, flies, moths, and ants) 4-10 mm in length over water, along forest edges, and over meadows and fields adjacent to trees. When feeding among insect swarms, this bat may catch 30 insects per minute, ingesting 3-4 g (0.11-0.14 oz) of food per hour.

Activity and Movement

The flight of this species is slow, erratic, undulating, and fluttering; resembling a moth or butterfly. When on a direct course, the average speed is 18.7 km/h (11.6 mph). Eastern pipistrelles remain active at least as late as October 5, for example near the Santanoni Gatehouse, Newcomb, but spend the winter hibernating within mines and caves where temperatures are 10-15 degrees C (50-60 degrees F), and humidity is high. Individuals tend to return to the same winter and summer roosts used in previous years. These roosts may be separated by a distance of 52.8 km (32.8 m). 


The reproductive biology of the eastern pipistrelle is not well known. Circumstantial evidence shows that mating may occur in the autumn and spring. Females store sperm from autumn matings, and fertilization takes place in the spring. The gestation period is 44-45 days. Females produce one litter per year, in July, of 1-3 (usually 2) young in the dark, warm recesses of buildings, tree cavities, rock crevices, or caves. The newborns are pink, hairless, blind and weigh 1-2 g (0.04-0.07 oz). For the first two weeks they cling to the female. At four weeks of age, they forage alone. Sexual maturation is from 3-11 months, the latter age likely for the Adirondack populations because of the shorter, warm season foraging period. Banding studies throughout the range of this species indicate a potential lifespan of 19 years for males (10 years for females), although few individuals attain these ages.


There is one record of a hoary bat killing and eating an eastern pipistrelle, and another of a leopard frog consuming this species.

Social Behavior

  • Social System - This species is promiscuous. Pregnant females gather in small maternal colonies of usually fewer than 12. In autumn, eastern pipistrelles engage in swarming near the entrances to hibernation sites. With these exceptions, this bat is normally solitary
  • Communication- The form and function of signaling is unknown. Adults have nasal glands which may provide chemical signals. Young produce clicking sounds that function in maintaining contact with their mother.  

Additional References

Fujita, M.S. and T.H. Kunz. 1948. Pipstrellus subflavus. Mammalian Species, 228:1-6.