The Bats of Pennsylvania


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Big Brown Bat (Eptesicus fuscus)

Second in size to the hoary bat, the big brown is 4.1-4.8 inches long; wingspread, 12.1-12.9 inches; weight, 0.420.56 ounces. The fur is dark brown, and the face, ears, and flight membranes are blackish. This common bat ranges throughout the state in diverse habitats: attics, belfries, barns, behind doors and shutters, hollow trees, in city and country.

Big brown bats fly at dusk, and generally use the same feeding grounds each night. They fly in a nearly straight course 20-30 feet in the air, often emitting an audible chatter.

Among the last bats to enter hibernation, big brown bats seek out caves, buildings, mines, and storm sewers in October, November, or December. They hang close to the mouths of caves. They emerge in March and April. Females bear young in June, usually two per litter. As young mature and leave the nursery colony, adult males enter and take up residence. Big brown bats have lived up to 19 years in the wild. Back to top

Big brown bats or the "Farmer's Friend" can be found during the day in certain barns and attics. At night they relentlessly feed over agricultural fields devouring crop pests.

Tri-colored bat (Perimyotis subflavus)

The tri-colored bat is also called the pygmy bat because of its small size: length, 2.9-3.5 inches; wingspread, 8.1-10.1 inches; weight, 0.14-0.25 ounces. Its fur is yellowish brown, darker on the back. The back hairs are tricolored: gray at the base, then a band of yellowish brown, and dark brown at the tip.

Tri-coloreds take wing early in the evening and make short, elliptical flights at treetop level. In summer, they inhabit open woods near water, rock or cliff crevices, buildings, and caves. They hibernate from September through April or early May, deep inside caves and away from the openings, in zones where the temperature is about 52-55 F. They sleep soundly, often dangling in the same spot for months completely covered with water condensation.

Tri-coloreds eat flies, grain moths, and other insects. They breed in November, and young-usually two per litter-are born in June or July. Pipistrelles live 10-15 years. They are found throughout Pennsylvania, except in the southeastern corner.

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The tri-colored bat is widespread in Pennsylvania but in low numbers. They are slow fliers and not often seen in the summer.

Hoary Bat (Lasiurus cinereus)

The largest bat of the eastern forests, the hoary is 5.1-5.9 inches long; has a 14.6-16.4-inch wingspread; and weighs 0.88-1.58 ounces. The fur is dark brown, heavily tinged and white. The species ranges across the state, but is uncommon.

Hoary bats roost in trees-they prefer conifers, but also use deciduous trees-in woods, forest edges, and farmland. They choose protected sites 10-15 feet above the ground. Strong, swift fliers, they take to the air later than most other bats. They prey mostly on insects, but occasionally take pipistrelles.

Hoary bats migrate to warmer climates in winter. In spring, they return and raise young. The young are born from mid-May to early July, usually two to a litter. The female gives birth while hanging in a tree. Young grow rapidly and are able to shift for themselves in about a month. Back to top


The Hoary is the largest bat found in Pennsylvania. It is only a summer resident; this bat may migrate 1,000 miles or more to overwinter.

Indiana Bat (Myotis sodalis)

The Indiana bat resembles the little brown bat, so much that the animal must be handled to closely examine differing characteristics. An Indiana bat has a pinkish cast to its fur, giving it a light purple-brown coloration. The muzzle has less fur giving its face a pink look compared to a little brown. The toes of the Indiana bat are distinctly curled and have short fine hairs which do not extend past the knuckles. A certain distinctive bulge on the edge of the tail membrane will complete a positive Indiana bat identification. Length, 2.9-3.7 inches; wingspread, 9.4-10.3 inches; weight, 0.18-0.28 ounces. Sexes are equal in size.

On right: Note less fur on muzzle of the Indiana bat, giving its face a more pinkish cast. The overall color of the fur also has a slight pink cast. Due to variations of the coloration of little browns and Indiana bats alike, the key to positive identification is careful inspection of the fine hairs on the feet and the edge of the tail membrane.

Indiana bats roost under the loose bark of trees in summer and have been found using buildings, roosting among common little browns. In winter, some 97 percent of the total species population hibernates in certain large caves in Missouri, Kentucky, Indiana, and Illinois. Pennsylvania is on the edge of the species' range. In our state in recent years, Indiana bats have been found wintering in only seven sites. The species has disappeared from all other known past localities. Populations of Myotis sodalis are dwindling throughout its range, and it is on the federal endangered species list.

The Indiana bat hibernates in clusters of about 250 bats per square foot on the ceilings and side walls of caves. In this formation, it is vulnerable to disturbance by cave explorers: when a bat on the edge of the cluster is awakened, it moves about, starting a ripple of activity that spreads throughout the group. A winter of repeated disturbances causes bats to burn vital fat stores, and they may run out of energy before spring.

Females of this species are believed to bear a single young in late June. Feeding habits are probably similar to those of the little brown bat. Back to top


A beautiful and powerful bat, the Hoary chooses deep forest habitat over man made structures.


The Indiana is the only federally endangered bat in Pennsylvania. Today 90% of the entire population survives the winter in just a handful of caves in the eastern United States.


Only a fraction of the historic Indiana bat population survives today. To make matters worse, they can be confused with common little brown and Northern long ear bats. The banded bat is an Indiana, how many more are there?

Little Brown Bat (Myotis lucifugus)

Pennsylvania's most common bat, the little brown is found statewide. Length, including tail, is 3.1-3.7 inches; wingspread, 8.6-10.5 inches; weight ranges from 0.25-0.35 ounces. Females are slightly larger than males. Color: a rich brown approaching bronze, usually with a dark spot on the shoulders. The fur is dense, fine, and glossy; the wings are black and bare.

This bat eats a wide variety of flying insects, including nocturnal moths, bugs, beetles, flies, and mosquitoes. Insects are regularly caught with the wing or tail membrane, and transferred to the mouth. An individual emerges from its day roost at dusk, and usually seeks a body of water, where it skims the surface for a drink, and then hunts insects. The little brown bat makes several feeding flights each night.

In October and November, bats leave their summer roosts and move to tunnels, mine shafts, and caves. Here, clinging to the ceilings and clustered against one another, they hibernate. In spring, they emerge in April and May. They return to the same hibernation sites year after year, usually to the same exact spot in the cave or mine.

Females disperse from the hibernation roosts, and gather in summer nursery colonies of 10 to l,000 individuals in attics, barns, and other dark, hot retreats. Males are solitary, roosting in hollow trees, under loose bark, behind loose siding and shingles, and in rock crevices.

A single young is born to each female in June or early July. After four weeks the young bat is fully grown and ready to leave the colony. Females mature sexually at about 8 months of age, while males mature in their second summer. Little brown bats may live up to 25 years. Back to top


Little browns are the most common bats in North America. They have adapted to human alteration of the natural landscape by using certain manmade structures to roost.

Northern Long Ear Bat (Myotis septentrionalis)

Similar in size and color to the little brown bat, A Northern long eared bat may be distinguished by its longer tail and narrow, long ears. It ranges throughout the state, but is much less common than the little brown bat; its distribution is considered local and irregular. Length, 3.0-3.7 inches; wingspread, 9.0-10.7 inches; weight, 0.25-0.32 ounces.

Zoologists have learned little of the ecology and behavior of Northern long eared bat; although they suspect feeding habits are similar to those of the little brown. Long eared bats roost singly or in small colonies in caves, behind window shutters, under loose tree bark, in cliff crevices. Females gather in nursery colonies in attics, barns, and tree cavities. Probably a single young is born in July. Long eareds return to caves in fall, often sharing space with little brown bats, big brown bats, and tri-colored bats. Back to top

Northern long ear bats are somewhat rare underground in Pennsylvania, but are commonly captured during the summer.


Longears sometimes prefer hibernating in narrow crevices and can be mistaken for little brown bats at a distance.

Red Bat (Lasiurus borealis)

A bright rusty coat and long, pointed wings distinguish this species. Length is 3.7-4.8 inches; wingspread, 11.3-12.9 inches; and weight, 0.28-0.49 ounces. Individuals roost singly in trees (except for females with young), often on forest edges, in hedgerows, and shrubby borders; they seem to prefer American elms. Rarely do they use caves or buildings.

Red bats start flying early in the evening, preying on moths, flies, bugs, beetles, crickets, and cicadas, which they take from air, foliage, and ground. Strong fliers, red bats are considered migratory, although their migratory patterns are little known. The sexes may migrate separately. Red bats start flying south in September or October.

Females bear 1-5 young (usually 2-3) in their treetop roosts. For the first few days, the young remain clinging to their mother when she flies out to hunt. Young are able to fly at 3-4 weeks, and are weaned at about 5-6 weeks old. Longevity is about 12 years . The red bat ranges across Pennsylvania. Back to top


Red bats are migratory, disappearing far to the south as winter arrives. They are widespread and relatively easily captured during the summer.

Silver-Haired Bat (Lasionycteris noctivagans)

A medium-size bat: length, 3.7-4.5 inches; wingspread, 10.512.1 inches; weight, 0.25-0.35 ounces. The fur is soft and long; the sexes are colored alike, blackish-brown tipped with white, for a bright, frosted appearance.

The silver-haired bat inhabits wooded areas bordering lakes and streams. It roosts in dense foliage, behind loose bark, or in a hollow tree-rarely in a cave. It begins feeding earlier than most bats, often before sunset. Silver-haired bats do not hibernate in Pennsylvania, migrating farther south. In summer, a few may breed in the cooler, mountainous sections of the state, but most go farther north. Back to top


Silver-haired bats are elusive forest dwelling migratory animals. A few are now known to hibernate at two sites in Pennsylvania.

Small-Footed Bat (Myotis leibii)

Also known as Leib's bat, this species is one of the smallest in North America: length, 2.8-3.3 inches; wingspread, 8.3-9.7 inches; weight, 0.18-0.28 ounces. In Pennsylvania, it is rare, and the population is thought to be decreasing; it is classified as a threatened species.

The small-footed bat resembles the little brown bat, but has a golden tint to its fur. Besides somewhat ill-proportionated small feet and forearms, this bat has a distinctive black "raccoon mask". Feeding and breeding habits probably parallel those of the other small, closely related bats. The small-footed bat waits until November to enter caves for hibernating, and emerges in March. It hibernates in narrow cracks in the wall or roof, singly and in small groups. It usually stays close to entrances or in areas where the temperature is just above freezing. Back to top


A state threatened species, the Small footed bat is seen only in very cold caves in the winter and very rarely in the summer. A distinctive "raccoon mask" and small feet identify this bat.

Note: The seminole bat (Lasiurus seminolus) and evening bat (Nycticeius humeralis) have been found a few times in Pennsylvania, but are considered incidental.

This information is adapted from the Pennsylvania Game Commission's Wildlife Note #175-35. Other Wildlife Notes on other animals are available through PGC, Bureau of Information and Education, Dept. MS, 2001 Elmerton Avenue, Harrisburg, PA 17110-9797.