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Missouri Bats

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Published on: Mar. 2, 2000

Last revision: Nov. 4, 2010

Bat Counts

Missouri is home to 14 kinds of bats. Although they are sometimes referred to as flying mice, bats are not rodents. They belong to a group of mammals called chiroptera, meaning "hand-wing," and are the only mammals that can fly.

The number and arrangement of bones in a bat's wing are the same as those of the human arm and hand. However, bat "finger bones" are greatly elongated and connected by a double membrane of skin that forms the wing.

Bats are clean, shy and intelligent creatures. They occupy almost every habitat worldwide and are the primary predator of many insect pests that cause millions of dollars of damage to farms and forests annually.

Bats of the World

There are almost 1,000 different kinds of bats, which comprise nearly one-quarter of all mammal species. Worldwide, bats vary in size from only slightly more than 2 grams to more than 2 pounds. The largest bats are called flying foxes and have a wing span up to 6 feet. Flying foxes live in southern Africa, India, islands of the South Pacific and northern Australia. Missouri bats range in size from 2 grams (1/10 ounce) to 42 grams (1 ounce). The largest bat in Missouri, the hoary bat, has a wing span up to 16 inches.

Bats in other parts of the world feed on a variety of food items. Many species feed primarily on fruit, while others feed on nectar and pollen. Some species eat the flesh of other animals, including fish, mice, birds, frogs, scorpions and even other bats. The most famous group of bats are the vampire bats of Mexico, Central America and South America; they feed on the blood of warm-blooded animals.

How Bats Eat

All Missouri bats feed exclusively on flying insects. Bats capture insects with their mouths or by scooping them into their wing or tail membranes. After scooping an insect up, the bat reaches down and takes it into its mouth. This method of feeding causes the darting and swooping motions that people associate with bats flying around lights near their homes at night. Because their insect prey also are flying, bats must maneuver and change directions quickly.

In addition to visually detecting prey, bats also rely on echolocation, a form of sonar. Bats emit pulses of high frequency sounds at a rate of a few to 200 per second. By listening to the echoes reflected back to them, they are able to "see" prey with their ears. Echolocation enables bats to capture small flying insects and to avoid obstacles in their path.

Bats drink water and are able to do so while in flight. As a bat skims over the surface of the water, it simply lowers its head and takes occasional gulps of water.

Hibernation

Because insects are not available as food during winter, bats in Missouri survive cold months by hibernating or migrating to warmer places. Hibernation is a state of rest in which heart and breathing rates are drastically reduced to help conserve energy. Bats reduce their body temperature from over 100 degrees F to the temperature of their hibernation site, usually 40-60 degrees F. The heart rate is slowed from over 1,000 beats per minute (bat in flight) to only one beat every four or five seconds.

A hibernating bat can survive on only a few grams of stored fat during its 5- to 6-month hibernation period. Bats usually lose one-fourth to one-half of their body weight during hibernation. Each time a bat is awakened, it may lose up to two months of stored fat reserves. Bats that are repeatedly disturbed are forced to emerge early from their roosts. If this emergence occurs before the insects have returned, the bats starve.

Just Hanging Around

When at rest, bats hang upside-down at their roost sites. This is because bats use gravity to gain enough speed to begin to fly. Some species of bats can't get airborne from a flat surface. By hanging upside down, they merely need to let go, pick up speed and start flapping their wings to begin to fly. This also allows them a quick escape if a predator approaches.

Reproduction

Most bats in Missouri breed in autumn, and the females store the male's sperm until the following spring, when fertilization takes place. The gestation period lasts only a few weeks and baby bats are born in May or June. Most female bats produce only one offspring (pup) per year, although some species give birth to three or four babies at a time. When pups are born, they are already one-half of their adult weight! The young are fed on milk until they are capable of foraging on their own. Baby bats grow rapidly, and most young are able to fly in two to five weeks.

Benefits of Bats

Bats are an important part of the natural world. Bats that feed on fruit are the primary means of seed dispersal for some species, and nectar-feeding bats are responsible for the pollination of many species of plants. In fact, more than 400 products used by humans come from bat-pollinated plants. These products include bananas, avocados, cashews, balsa wood and tequila.

Missouri bats help control nocturnal insects, some of which are agricultural pests or, in the case of mosquitoes, annoying to people. Many forms of cave life depend on the nutrients brought in by bats and contained in their guano.

Bat Myths

Bats have been the subject of folklore and superstitions for thousands of years. Their habit of sleeping in caves and flying at night have helped to promote myths about bats. Those stories leave us with the impression that bats are nasty and filthy animals that possess the supernatural power of shifting shape from bat to man. Movies in which bats turn into blood-sucking vampires have increased people's fear of bats.

Such misinformation has resulted in needless and senseless persecution of bats. The beliefs that bats are blind or that they will fly into your hair are simply not true. Bats see quite well; they just don't see colors. They are also able to detect and avoid objects as fine as a single human hair.Bats are commonly feared because they can carry rabies. Although rabies is a serious disease, it occurs in only a small percentage of bats (less than 1/2 of 1 percent). Bats that contract the disease die quickly and rarely show the aggressiveness shown by rabid dogs and cats. As with any wild animal, if a bat allows you to approach it, the animal is probably sick and should be avoided.

Endangered Bats

Worldwide, many bat populations are declining at an alarming rate. Special methods of protection have been established to help protect these dwindling populations. Two Missouri cave bat species, the gray bat and the Indiana bat, are listed as federally endangered by the U.S. Fish and Wildlife Service and state endangered in Missouri.

Ozark big-eared bats (Corynorhinus townsendii ozarkensis), which used to live in caves in southwestern Missouri, have not been observed in Missouri since 1971. This species, also state and federally listed as endangered, lives only in a few caves in northwestern Arkansas and northeastern Oklahoma. The Ozark big-eared bat was listed as endangered because of its small population, reduced distribution and vulnerability to human disturbance. Habitat loss and disturbance at maternity caves and hibernation sites are likely causes of its decline.

Conservationists are taking protective management measures to assist in the protection of these species. These include gating or fencing important bat caves and placing warning or interpretive signs at other caves to minimize human disturbance.

BAT BIOLOGISTS

To avoid disturbing bats unnecessarily, the Conservation Department allows just two biologists to census hibernating gray and Indiana bats, and then only on a two-year cycle.

Every winter biologist Rick Clawson (top) takes precise temperature readings of the air near the bats and the bedrock to which they attach. They count small clusters individually, and measure larger ones, multiplying them by a known bat-density factor--about 170 per square foot for grays, and 400-500 for Indianas. Only 44 hibernacula are known for these bats in Missouri, but others may remain undiscovered.

In summer, gray bats occupy about 64 maternity caves, where larger rooms and warm conditions are suitable for bearing young. Entering a maternity colony is harmful to the bats, so Conservation Department researchers (from left) Clawson, Norman Murray & Brian Loges visit some of the sites in the fall, after the bats have left, to measure the area of fresh guano (center), which is distinguished by a darker color, presence of fungi and other characteristics.

Recently, Conservation Department bat biologist Bill Elliott placed electronic temperature dataloggers in bat caves to record the temperature variation at bat roosts.

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