Big Brown Bat
Phylum: Chordata (organisms that possess a structure called a notochord)
Class: Mammalia (3 middle ear bones; hair; and the production of milk by modified sweat glands
called mammary glands.)
Order: Chiroptera (winged)
Family: Vespertilionidae (This is the largest family of bats: it includes 35 genera and 318 species! With this many species there are exceptions to almost every generalization about this family; mouse-eared bats)
Genus: Eptesicus (Big Brown Bat)
Species: Fuscus (Dusky; greyish brown in color)
The Big Brown Bat, despite it’s name is a medium sized bat. It has a forearm of about 2 inches, and it’s wingspan is about 12 inches. This particular bat is uniformly dark brown above in Eastern North America and tends to be pale brown in the West. His bottom side is a creamier brown. Furthermore this bat has a large, broad head, husky body, short, rounded ears, along with short, broad wings. He is overall brown in appearance with a soft, and somewhat oily pelage, it’s hair is relatively long and lax. It has large and bright eyes and a broad rounded tragus.(the fleshy, cartilage protrusion at the front of the external ear, partly extending over the opening of the ear. The naked parts of ears, face, wings, and tail membrane are blackish. The total length ranges from 87 – 138 mm and mass is from 11 – 23g. Females are slightly larger in size than males. Younger bats are darker and duller than adults. Big Brown Bats have a strong flight with sudden frequent changes in direction. The noise this bat makes has been described as escaping steam, a clicking, and as a body vibration when at rest. Bats live for up to 19 years, and males generally live longer than females.
The Big Brown Bat exists throughout most of North America, Central America, and the Antilles, and reaches its southern limit in northwestern South America.(see map at right of previous page) Generally, the Big Brown Bat is restricted to the forested highlands in the arid southwestern United States. We do have Big brown bats in Michigan. The Big Brown Bat’s habitat ranges from cities to the wilderness, and sea level to mountains. They live in caves, mines, trees, bridges, crevices, and as many of us know, buildings.
Although a bat appears to be bird-like, it does not lay eggs. All bats give birth to one or two naked young a year. A newborn bat has well developed feet and claws that it uses to cling to its mother or to roost when the mother leaves to eat. Disturbances of maternity roosts can result in large numbers of young bat deaths. When disturbed, the mother bat becomes excited and flies, jerking the young bats and causing them to fall. Copulation between pairs occurs between September and March. Ovulation and fertilization is delayed until after arousal from hibernation in temperate populations. Gestation is about 60 days; one young is usually born in the west, two in the east and Cuba. Births occur from May to July. Young at birth are naked, have closed eyes, and weigh only one tenth of an ounce. They are weaned at 3 weeks and attain adult size in 2 months. Bat mothers roost in caves with millions of other nursing mothers, thousands of pups are left hanging from ceilings when their mothers go out to hunt. Using special sonar mother bats can identify their own pup from the thousands of others. Little is known about the social habits of bats. Groups of four to six may hibernate together in the colder months, while during the summer bats have been found to be mostly solitary. Bats enter into hibernation late and emerge early, some migratr before hibernation. The Big Brown Bat is the only bat in the United States and northward that hibernates regularly in houses.
Big Brown Bats gobble up as many as 3,000 insects a night. Foraging occurs throughout the night with the greatest amount of activity 2 hours after sunset. The Big Brown Bat is a generalist in foraging habitat; it shows no preference for over-water versus over-land sites, edge versus non-edge habitats, full canopy versus no canopy, and rural versus urban environments. Small beetles are the most common prey; wings may be culled before ingestion. Bats mostly catch their food in mid air. Although bats can see they rely more on their ears. Bats use echolocation to locate their prey. Echolocation is the use of the echoes of sounds produced by certain animals to detect obstacles in their paths. The sounds bats make “bounce off” objects and they hear an echo, they use this echo to determine where the bug is.
Many people fear bats. They have heard rumors of rabies and other diseases bats carry. Bats are surprisingly very helpful to our lives. Brown bats can consume half their weight in insects in just one night. Bats are the biggest hunters of night-flying insects, Including mosquitos. Bats can catch more than 500 mosquitos in one hour. There’s something to think about the next time you feel yourself scratch a mosquito bite. Bats droppings also produce a valuable fertilizer called Guano. Bats are food to predators such as grackles, kestrels, owls, cats, and rats. Although bats can carry rabies, very rarely is anyone bitten by them. If a bat is able to be touched by a human, then it more than likely has something wrong with it, which could include rabies. This is when bats will bite, and this is where the rumors come from. It is not true that bats carry common lice or bedbugs. Bat parasites only attack bats, and are therefore harmless to humans. Bats can actually be kept as pets. They can be used to catch pesky insects and their droppings can be used for fertilizer. Big Brown Bats in particular have a well-documented homing ability, and take well to captivity. Bats play an important part in controlling the insect population. Bats are very misunderstood, if you leave them alone they will leave you alone.
Big Brown Bat Bibliography
“Big Brown Bat” Amazing Animals of the world, 1995
Burt, William Henry Mammals of the Great Lakes Region.New York:Vali-Ballou Press Inc., 1957
Collins, Henry Hill Jr. Field Guide to American Wildlife. New York: Harper and Row, 1957
Comptons Interactive Encyclopedia. Comptons New Media, 1995
Eptesicus fuscus [big brown bat]: http://www.oit.itd.umich.edu/bio/doc.cgi/Chordata/Mammalia/Chiroptera/Vespertilionidae/Eptesi cus_fuscus.ftl, Microsoft Internet Explorer, 1997
Palmer, Ralph S. The Mammal Guide. New York: Doubleday, 1954
http://sevilleta.unm.edu/data/species/mammal/socorro/profile/big-brown-bat.html, Microsoft Internet Explorer, 1997
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