image of batOnly in the last 50 years has man learned much about bats and their life history. Their nocturnal habits, affinity for eerie places like caves, and silent, darting flight have made them the subjects of a great deal of folklore and superstition through the years. Active at a time when most people prefer to be indoors and able to function when and where man's most important sense, sight, is denied him, it is no wonder that bats seem supernatural. Actually, bats are superbly adapted creatures that have evolved to exploit resources such as night-flying insects and dark caverns that are unavailable to diurnal and sightsee animals.

Bats are the only mammals capable of true flight. Their fore limbs have the same configuration as other mammals', but the bones of the fingers are greatly elongated to support membranous wings. The hind limbs are modified to allow them to alight and hang, head-down, by their toes.

Bats feed at night. Most locate their food and navigate by uttering a continuous series of ultrasonic cries that return as echoes when the cries hit solid objects. In the daytime they seek shelter in a wide variety of places: caves, mines, buildings, rock crevices, under tree bark and amid foliage. When resting and hibernating, bats can lower their body temperature to nearly match the environment and thus lower their metabolism and conserve energy.

Most bats congregate in nursery colonies in the spring. The young are born in May or June. Most Missouri bats produce one young per year; several species produce two, and one produces up to four. the young are fed on milk until they are capable of foraging on their own. Summer colonies disperse in July and August, when the bats begin migration to hibernation sites. A variety of sites are used for hibernation--caves, mines, buildings and hollow trees. Before hibernating, bats accumulate fat reserves to last throughout the foodless winter.

Bats are an important part of the natural system. They help control nocturnal insects, some of which are agricultural pests or annoying to man. Many forms of cave life depend upon the nutrients brought in by bats and released from their guano (feces). And bats have contributed much to man's knowledge through scientific studies of their echolocation abilities, their biology and certain aspects of their physiology.

Bat populations have been declining at an alarming rate in recent years. Some of the more important causes of this decline are destruction of habitat, pesticides and disturbance. Loss of roosting and foraging habitat has resulted from reservoir construction, watershed development, forest conversion, urbanization and cave commercialization. Lethal levels of pesticides have been found in dead bats in several studies. Vandalism and disturbance have eliminated or greatly reduced bats in a number of caves. Three species of bats in Missouri are on the federal Endangered Species List and are protected by the Endangered Species Act of 1973. All bats are protected by the Wildlife Code of Missouri.

All of the bats that occur in Missouri are insectivorous. They can be divided into two groups--those that roost only in trees and those that spend at least a portion of the year in caves.

Among the tree bats, red bats and hoary bats roost amid the leaves while silver-haired bats roost under loose bark and evening bats prefer cavities. Red bats are probably the most commonly seen species in the state. Occurring statewide, they emerge at dusk to forage along woods edges, over streams, along roads and frequently around street lamps in towns. In winter, they may be seen on warm afternoons foraging in forest openings. The hoary bat, so named because of white tips on its rich, dark brown fur, is the largest Missouri bat, weighing over an ounce and having a 15-inch wingspan. Silver--haired bats are primarily a northern species while evening bats raise young in Missouri but migrate south for the winter.

The remaining species occupy caves all or part of the year. Gray bats, Indiana bats and Ozark big-eared bats are on the federal Endangered Species List. Gray bats and Indiana bats are threatened with extinction largely because of their habit of amassing in very large numbers (up to hundreds of thousands) in only a few caves. Thus they are extremely vulnerable to disturbance (each time they are awakened from hibernation they use up vital fat reserves), destruction from natural catastrophes such as flooding or wanton slaughter by people, and loss of important caves to commercialization, inundation by reservoirs, or other causes. There now may only be a few hundred Ozark big-eared bats in existence. They are known from only a very few caves in southwest Missouri, northwest Arkansas and eastern Oklahoma.

Gray bats live underground year-round and thus are found only in areas with suitable caves (mostly the southern half of the state). Their summer caves are easily recognized because of the huge mounds of guano that accumulate beneath the bat roosts. The roosts themselves usually are evident as brown stains on the cave ceiling. In June and July, when flightless young are present, disturbance can lead to mass mortality as frightened females drop their young in the panic to flee from the intruder. Such clusters of gray bats are usually noisy, so if you enter a cave with a strong guano smell and hear bats, please turn around and leave immediately. Gray bats are known to hibernate in four caves in Missouri; three of them have pit (vertical) entrances that make human access difficult thus limiting disturbance. One of these caves is commercialized, but the owners are taking steps to protect the bats.

Indiana bats hibernate in a few cold caves in the Ozarks, and more than half of the entire world population winters in Missouri. They form dense cluster of hundreds or thousands of bats on cave ceilings, usually within or just beyond the twilight zone near the cave's entrance. At this time they are highly susceptible to disturbance by cave explorers. In summer, Indiana bats disperse and form small colonies. They live under tree bark and are not likely to be seen. Relatively little is known about their summer ecology because they are so difficult to locate.

Little brown bats hibernate in small numbers in many caves in Missouri. In summer, they sometimes form colonies in barns and attics. Keen's bats hide in crevices in caves and are rarely seen even through numbers of them can be trapped at cave entrances at night.

Eastern pipistrelle bats are pale in color and can be found hibernating singly in most caves in the state. Big brown bats hibernate in cold sites just inside cave entrances. They sometimes form colonies in barns and attics where their guano may create an odor problem. when a single bat is found inside a house, it is most likely a big brown that entered looking for a place to roost for the day.

At present, bat management consists primarily of protecting habitat. Some of the caves known to be occupied by endangered species have been acquired or leased. Caves that are especially critical to the survival of these species are being gated with welded steel bars set in concrete or rock. However, during the times of the year when the endangered bats are not present, these caves can be visited without harm to the bats. Many caves used by endangered bats are posted with signs that explain which species is present and at what time of year entrance into the cave would disturb the bats. They also give some information on why the bats need protection. Entering a bat cave could lead to prosecution under the Endangered Species Act and bring a fine of up to $20,000.

If you have bats in your house or other building and wish to evict them, the best method is to block all access holes when the bats are out so that they cannot return. The best time is in the fall or winter after the bats have left for hibernation. Alternatively, you could wait until the bats have left to forage at dusk and then block up the holes. However, don't do this between May 15 and July 15 when flightless young might be present as they would die and create an additional odor problem. Killing the bats without stopping up their access holes may alleviate the problem for the time being, but the conditions that attracted the bats in the first place would still exist and other bats probably would use the site in the future. It has recently been found that spraying pesticides on a bat colony is not a good method of control, for several reasons--(1) not all the bats are killed, (2) dying bats fall near the treatment site and are likely to come in contact with humans and their pets, and (3) as above, the conditions that initially attracted that bats are not changed.

Appendix I gives a simple key and descriptions of the cave bats most likely to be encountered in Missouri. It also has identification tips to help distinguish the two endangered Myotis species from other, similar bats. Also attached is a page of drawings that depict several key characters to separate bats of the genus Myotis in Missouri. If you encounter endangered species or find any bats with numbered plastic bands on their wings, please send the number, color of band, date, locality and any other pertinent information to Richard Clawson, Fish and Wildlife Research Center, 1110 College Avenue, Columbia, Missouri 65201.

Bats need friends. They have suffered from misinformation and superstition for years. As we learn more about these furry little "angels of the night" we realize their importance in the natural scheme of things. An enlightened public, realizing that the system is composed of many parts and that each has a role to play in maintaining the balance, will ultimately prove to be the bat's best friend.

This publication is made possible by the 1/8 of 1% sales tax dedicated to conservation in Missouri.

APPENDIX I - A SIMPLIFIED KEY TO MISSOURI CAVE BATS

A. Usually roosting in large clusters (hundreds or thousands)

  1. Fur on back gray; guano piles under cave roosts; bats usually seen only in spring, summer or fall - Gray Bat
  2. Fur on back brownish gray; no guano piles under roosts; bats usually seen only in cold caves in late fall, winter and early spring - Indiana Bat

B. Usually roosting singly in or in very small clusters (fewer than 20)

  1. Large size (total length 4" to 5"); fur on back dark brown - Big Brown Bat
  2. Small size (total length less than 4")

a. Fur on back pale yellowish or pale reddish-brown - Pipistrelle Bat

b. Fur on back dark glossy brown

  1. Ears long (about 3/4") - Keen's Bat
  2. Ears shorter (usually 5/8" or less) - Little Brown Bat

A MORE DETAILED GUIDE TO IDENTIFICATION AND HABITS OF MISSOURI CAVE BATS

line drawing of bat anatomy

Gray Bat (Myotis grisescens) -- ENDANGERED --

Indiana Bat (Myotis sodalis) -- ENDANGERED --

Little Brown Bat (Myotis lucifugus) --

Keen's Bat (Myotis keenii) --

Big Brown Bat (Eptesicus fuscus) --

Eastern Pipistrelle Bat (Pipistrellus subflavus) --

IDENTIFICATION OF INDIVIDUAL BATS IN THE HAND

Identification of individual bats in hand can be difficult. The key to Missouri cave bats may prove adequate, especially if roosting conditions were observed. Otherwise the following drawings may be very useful. They use the color of the fur, as revealed by blowing in the center of the back to part the fur; the position of attachment of the tail membrane; the length and density of distribution of hairs on the toes; and the degree of development of a fleshy keel on the calcar, which is a cartilaginous supporting structure on the rear edge of the tail membrane. These are the characteristics used by bat biologists to distinguish among these species.

Content revision: 20030731