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Flying Mammals |
PA Bats |
Bats & Windpower
Pennsylvania Bats
All Pennsylvania bats belong to the family Vespertilionidae, the most common family of bats in North America. Also called evening bats, this group is primarily made up of nocturnal hunters of flying insects. They usually feed in open areas, especially near water, where insects swarm. Because their food supply is not available when temperatures drop, Pennsylvania bats either hibernate or migrate for the winter months.
There are nine different bats common to Pennsylvania:
| Little Brown Bat (Myotis lucifugus) |
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The little brown bat is the most common bat in Pennsylvania. Myotis means “mouse-eared” and lucifugus “light-fleeing” referring to its short rounded ears and nocturnal lifestyle. In the summer, males remain solitary and may be found roosting in a variety of places, including buildings, hollow trees, caves, and rock crevices. Females form nursery colonies of up to 1000 or more individuals in attics, barns, or other places that provide the hot temperatures their young need to grow. In June, each female usually bears a single pup. Little browns prefer to roost near water. Before they begin hunting for the evening, they fly low over a stream or lake for a drink of water on the wing. They become active at dusk and will travel up to six miles from their roost on nightly feeding flights. A little brown bat can catch up to 1200 mosquitoes in one hour! Each October, little brown bats return to the same cave or mineshaft to hibernate for six to eight months before emerging again in April or May. Little brown bats are the longest-lived mammals for their size and may live for over 30 years.
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| Indiana Bat (Myotis sodalis) |
Hibernating
Note the Transmitter on the Back of an Indiana bat |
The Indiana bat so closely resembles the little brown bat that it must be carefully examined carefully to properly identify it. Sodalis, the Latin word for “companion,” describes the social nature of the Indiana bat, which clusters together in large numbers during hibernation. There are 300 known hibernation sites in 26 states, but over 90 percent of the bats hibernate in a few large caves in Indiana, Missouri, Kentucky, and Illinois. Because they hibernate in such large groups, they are very vulnerable to disturbance. They also require specific temperature and humidity conditions for hibernation, found at very few sites. In the summer, females form small nursery colonies of up to 100 individuals, which are frequently located under the bark of dead or dying trees. In 1967, the Indiana bat became one of the first bat species in the U.S. to be listed as federally endangered. The listing was largely due to data recorded at hibernation sites, because little was known about their summer habitats. Since its listing, the population has decreased by 60 percent. Disturbance of hibernation caves, loss of summer roosting and foraging habitat, and possibly pesticide poisoning have all contributed to the decline of the Indiana bat. There are approximately 280,000 Indiana bats remaining in the U.S.
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Eastern Small-footed Bat (Myotis leibii)
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The eastern small-footed bat can weigh as little as 0.1 ounces, about the weight of a ruby-throated hummingbird, making it the smallest bat in eastern North America. They could easily be mistaken for large moths because they also have a slow, fluttering flight pattern. Despite their small size, they are among the hardiest of bats. They are some of the last to enter hibernation in the fall and often stay close to cave entrances where temperatures are just above freezing. Eastern small-footed bats tend to hibernate individually, often tucked into small cracks and crevices in caves and may go unnoticed during surveys. The largest hibernating population found in the state numbers less than 50 bats. Because they are rare and little is known about them, the eastern small-footed bat is listed as threatened in Pennsylvania. Protecting these bats from disturbance during hibernation is considered key to their survival.
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Northern Long-eared Bat (Myotis septentrionalis)
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The northern long-eared bat resembles the little brown bat, except that it has, as its name implies, longer ears. Long-eared bats prefer forested habitats and like to roost alone or in small groups. Relatively little is known about them, but it is believed that their habits may be similar to the little brown bat. Although the long-eared bat is found throughout Pennsylvania, it is much less common than the little brown.
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Big Brown Bat (Eptesicus fuscus)
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This is the bat most likely to fly through an open window into your home at night. Big brown bats are closely associated with humans, because they frequently roost in buildings in both country and city settings. This may explain the name Eptesicus, meaning "house flier." In the summer, big browns roost in attics or barns, under eaves, behind shutters, or in hollow trees. They are extremely tolerant of cold and enter hibernation as late as November or December. They are the only North American bat that commonly hibernates in walls or attics. Big browns also hibernate in caves and mines, but prefer to stay in cooler spots near the entrance. The big brown bat is the second largest bat in Pennsylvania. They are slow, steady fliers that follow a nearly straight path at 20 to 30 feet in the air to their foraging spots. Many visit the same feeding grounds each night. Big browns eat a variety of insects, but their favorite food is large beetles.
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Eastern Pipistrelle (Pipistrellus subflavus)
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The eastern pipistrelle, also called the pygmy bat, is one of the smallest bats in Pennsylvania. Pipistrellus is from the Italian word for “bat.” Subflavus is Latin for “almost yellow” which refers to the pipistrelle's beautiful, tri-colored fur that is gray at the base, yellow in the middle, and brown at the tip. The pipistrelle is also called the butterfly bat, because of its erratic, fluttering flight. It leaves its roost in early evening to hunt in forests and along the edges of woodland streams. They are sometimes preyed upon by hoary bats, leopard frogs, and owls. Pipistrelles are among the first to hibernate in the fall and the last to emerge in the spring. They tend to hibernate singly and select deeper parts of the cave where temperatures are fairly constant. During hibernation they are frequently found covered with water droplets, because their bodies become so cool that moisture condenses on their fur. Due to reproductive requirements, these bats will still hibernate in southern areas, like Florida, where food is available and temperatures remain warm year round.
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Silver-haired Bat (Lasionycteris noctivagans)
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The silver-haired bat has long, blackish fur with silvery-white frosted tips, making it easy to identify. They prefer coniferous and mixed forests to open country. They roost alone under bark, in hollow trees, among foliage, in woodpecker holes, and even birds' nests. They can often be seen foraging before sunset along the edges of streams or ponds. Silver-haired bats are among the slowest flying bats in North America. In Pennsylvania, most silver-haired bats migrate, although a few have been found hibernating.
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Red Bat (Lasiurus borealis)
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The bright rusty fur of the red bat makes it one of the most beautiful bats. Except for their ears and parts of their wings, these bats are fully furred—even their tails are furry. Lasiurus means “shaggy tail.” On summer days they hang by one foot among the foliage of trees, often resembling a dead leaf. They are early evening fliers and hunt close to their roosts. Especially fond of moths, they can often be seen catching them near street lights. Unlike most bats, red bats can have up to four young. Females and young usually remain among the trees, rather than forming nursery colonies. In Pennsylvania, the red bat is mainly a migratory species traveling as far south as Bermuda and the Caribbean. They are strong fliers and can reach speeds of up to 40 mph.
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Hoary Bat (Lasiurus cinereus)
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The hoary bat is the largest bat in eastern North America, with a wingspan of up to 16 inches. Their markings are very distinctive and handsome. They are covered with silvery (“hoary”) fur, brown with frosted tips, and have a yellow collar at the throat. The hoary bat is the most widespread American bat, found across the country, and is the only native land mammal to Hawaii. While they are found throughout Pennsylvania, they are uncommon here. Hoary bats are solitary, forest-dwellers with similar habits as the red bat. They emerge late in the evening and are swift, strong fliers that can reach speeds of 60 mph. They are primarily insect eaters, preferring moths, but will occasionally eat smaller bats. Female hoary bats are very loyal to their roosting sites. If undisturbed, they may return to the same tree each year to raise their young. Although they are extremely tolerant of the cold, it is believed that most Pennsylvania hoary bats migrate to southern areas for the winter.
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