|
Introduction to Bats
Bats may be the most misunderstood animals in the United States, although as consumers of enormous numbers of insects, they rank among the most beneficial. Almost all United States bats, and 70 percent of the bat species worldwide, feed almost exclusively on insects and are thus extremely beneficial. In fact, bats are the only major predators of night-flying insects. One bat can eat between 600 and 1,000 mosquitoes and other insect pests in just one hour (Organization for Bat Conservation). While most United States bat species are insectivorous, bats in other parts of the world feed on a variety of items in addition to insects. Many species feed primarily on fruit, while several types feed on nectar and pollen. Fruit bats perform an extremely important function as seed dispersers. Nectar eating bats, including the federally-listed endangered lesser long-nosed (Leptonycteris curasoae yerbabuenae) and greater Mexican long-nosed bats (Leptonycteris nivalis), are important pollinators. Many plant species depend almost entirely on bats for pollination. Of the 45 species of bats found in the continental United States, six are federally-listed as endangered under the Endangered Species Act of 1973, as amended. These species include the gray bat (Myotis grisescens), Indiana bat (Myotis sodalis),Ozark big-eared bat (Corynorhinus (=Plecotus) townsendii ingens), Virginia big-eared bat (Corynorhinus (=Plecotus) townsendii virginianus) as well as the two long-nosed bats mentioned above. In addition to the listed continental U.S. species, the Hawaiian hoary bat (Lasiurus cinereus semotus)(Hawaii), little Mariana fruit bat (Pteropus tokudae)(Guam) and Mariana fruit bat (Pteropus mariannus mariannus)(Guam), are also listed as endangered. Twenty other species are considered to be of special concern and may be proposed for listing as endangered or threatened in the future. Populations of several of the remaining species, especially cave-dwelling species, also appear to be declining. Common Misconceptions About Bats
“All Bats Have Rabies.” Less than ½ of 1% of bats carry the rabies virus (University of Florida). In addition, rabid bats are seldom aggressive. Fewer than 40 people in the United States are known to have contracted rabies from bats during the past 40 years. Far more people are killed by dog attacks, bee stings, power mowers, or lightning than rabies from bats. However, rabies is a dangerous disease so you should avoid direct contact with bats as well as other wild animals. The Center for Disease Control, USFWS, and Bat Conservation International have cooperatively developed a public health guide: Bats and Rabies. “Bats get tangled in peoples hair.” Although bats may occasionally fly very close to someone's face while catching insects, they do not get stuck in people's hair. That's because the bats ability to echolocate is so acute that it can avoid obstacles no wider than a piece of thread. “Bats suck your blood.” By far the most famous bats are the vampire bats. These amazing creatures are found in Mexico, Central America and South America. Vampires feed on the blood of warm-blooded animals such as birds, horses and cattle. Vampire bats do not suck blood. The bats obtain blood by making a small cut in the skin of a sleeping animal with their razor-sharp teeth and then lapping up the blood as it flows from the wound. There is an anticoagulant in the bat's saliva that helps to prevent the animal's blood from clotting until the bat has finished its meal. The bat's saliva also contains an anesthetic that reduces the likelihood of the animal feeling the prick. Each bat requires only about two tablespoons of blood every day, so the loss of blood to a prey animal is small and rarely causes any harm. “Bats are rodents.” Bats may resemble rodents in many ways, but they are not rodents. In fact, there is recent evidence that bats may be more closely related to primates (which include humans) than to rodents (Museum of Paleontology, University of California at Berkeley). “Bats are blind.” Although they can't see color, bats can
see better than we do at night (University of California at
Berkeley). And, many bats can also “see” in the dark by using echolocation. Bat Biology
Bats, like humans, are mammals, having hair and giving birth to living young and feeding them on milk from mammary glands. More than 900 species of bats occur worldwide; they are most abundant in the tropics. Bats are second only to rodents in numbers among mammals and comprise about one-fifth of all mammal species. Worldwide, bats vary in size from only slightly over two grams (0.07 ounce - about the weight of a dime) to more than 1.5 kilograms (more than 3 pounds). The large "flying foxes" of Africa, Asia, Australia, and many Pacific islands may have a wingspan up to two meters (6 feet). United States bats vary in size from less than three grams (0.11 ounce) to 70 grams (2.5 ounces). The largest United States bat, the greater mastiff bat (Eumops perotis) occurring from central California south into Mexico, has a wingspan of approximately 55 centimeters (22 inches). Bats are the only true flying mammals, and their maneuverability while capturing insects on the wing is astonishing. Bats belong to the mammalian order Chiroptera, which means "hand-wing." The bones present in a bat's wing are the same as those of the human arm and hand, but bat finger bones are greatly elongated and connected by a double membrane of skin to form the wing. Bats primarily are nocturnal, although many fly early in the evening, sometime before sunset. Occasionally, especially on warm winter days, they are observed flying during daylight hours. Reproduction and Longevity. Most female bats produce only one offspring per year, although some species give birth to three or four babies at a time. Most United States bats breed in autumn, and the females store sperm until the following spring when fertilization takes place. The gestation period (pregnancy) lasts only a few weeks, and baby bats are born in May or June. They develop rapidly, and most can learn to fly within two to five weeks after birth. Bats live relatively long lives for animals of their small size, some as long as 30 years. Echolocation. Although bats have relatively good eyesight, most depend on their superbly developed echolocation (or sonar) system to navigate and capture insects in the dark. Bats emit pulses of very high-frequency sound (inaudible to human ears) at a rate of a few to 200 per second. By listening to the echoes reflected back to them, they can discern objects in their path. Their echolocation ability is so acute they can avoid obstacles no wider than a piece of thread and capture tiny flying insects, even in complete darkness. Feeding. Insect-eating bats may either capture flying
insects in their mouths or scoop them into their tail or wing membranes. They
then reach down and take the insect into their mouth. This results in the
erratic flight most people are familiar with when they observe bats flying
around in the late evening or around lights at night. Bats drink by skimming
close to the surface of a body of water and gulping an occasional mouthful. Hibernation and Migration
Hibernation and Migration. Because insects are not available as food during winter, temperate-zone bats survive by either migrating to warmer regions where insects are available, or by hibernating. Hibernation is a state of torpor (inactivity) during which normal metabolic activities are greatly reduced. Body temperature is reduced and heart-rate is slowed. A hibernating bat can thus survive on only a few grams of stored fat during the approximately five-to-six month hibernation period. Bats usually lose from ¼ to ½ their body weight during hibernation. Several bat species hibernate in dense clusters on cave walls or ceilings. Clusters may consist of hundreds of bats per square foot. Summer "maternity" colonies of pregnant or nursing females of several species also congregate and cluster together. Most United States cave bats spend winter hibernating in caves (or mines) and move to trees or building during summer. A few species reside in caves year-round, although they usually use different caves in summer than winter. Most cave bats are very loyal to certain caves and return year after year to the same caves, often to the exact location in the cave where they spent the previous winter. Tree bats seldom enter caves. They roost in trees during summer
days and spend winter primarily in hollow trees. Several species make relatively
long migration flights between winter and summer habitats. The millions of
Brazilian (or Mexican) free-tailed bats (Tadarida brasiliensis) that
spend the summer in southwestern United States caves, such as Carlsbad Cavern in
New Mexico, migrate up to 1,300 kilometers (800 miles) to and from their winter
roosts in Mexico. Reasons for Decline
Several animals, including owls, hawks, raccoons, skunks, and snakes prey on bats; yet, relatively few animals consume bats as a regular part of their diet. Man seems to be the only animal having significant impact on bat populations. Adverse human impacts include habitat destruction, direct killing, vandalism, disturbance of hibernating and maternity colonies, use of pesticides (on their food - insects), and other chemical toxicants. Drastic reductions in bat populations have occurred during recent years in the United States and worldwide. Human disturbance to hibernation and maternity colonies is a major factor in the decline of many bat species. Even well meaning individuals such as cavers and biologists cause these disturbances. Hibernating bats arouse from hibernation when disturbed by people entering their caves. When aroused, they use up precious winter fat needed to support them until insects are again available in spring. A single arousal probably costs a bat as much energy as it would normally expend in two to three weeks of hibernation. Thus, if aroused often, hibernating bats may starve to death before spring. Disturbance to summer maternity colonies also is extremely detrimental. Maternity colonies won't tolerate disturbance, especially when flightless newborn young are present. Baby bats may be dropped to their deaths or abandoned by panicked parents if disturbance occurs during this period. In some parts of the world, especially in parts of Asia, Africa, and the Pacific Islands, many bat species are used as food by humans. There is concern that many food species may become extinct due to overharvest and lack of adequate management. This is true not only for the larger "meatier" species such as fruit bats, but for smaller bats as well. Indiana Bat
Frequently Asked Questions
What are the
Characteristics of the Indiana Bat?
It has pink lips, extended tragus (projection in the ear), and bi-color hair, dark at the base and light on the ends. How does the Indiana Bat benefit the environment? The Indiana Bat's diet is insects. The bats help to keep insect numbers under control and eat nuisance and pest insects like alfalfa weevils and gypsy moths. Their presence adds to the biological diversity of forest communities. What is being done to protect the Indiana Bat? Habitat Enhancement: US Forest Service (US Dept. of Agriculture) actively manages watersheds and forests to provide Indiana Bat habitat including sources of water, roosts and forage areas. Bat-friendly gates have been installed in key breeding sites. Collaboration continues with federal, state and private organizations to improve bat habitat rangewide. Consultation: US Forest Service consults both informally and formally with US Fish and Wildlife Service (USFWS - US Department of Interior) whenever new issues develop to ensure that new information is considered and that projects maintain or enhance the bats' conservation and recovery. Recovery Plan: USFWS developed a recovery plan in 1976, followed by a revision in 1983. A newly revised recovery plan for the Indiana Bat is due out in 1999. Research: Research continues to investigate the cause(s) of the dramatic decline of Indiana Bats populations and appropriate actions necessary to conserve this species. What is the scientific name of the Indiana Bat? Myotis sodalis. Myotis comes from two Greek words meaning "mouse ear" and sodalis comes from the Latin word for "companion," which refers to this bat's habitat of hibernating in large groups known as clusters. It is also referred to as the "social" bat because of its habit of congregating. What is the range of the Indiana Bat? The Indiana Bat is found over most of the eastern half of the US. However, most large hibernating populations are found in Indiana, Missouri and Kentucky. What is the habitat of the Indiana Bat? Indiana bats hibernate during winter in caves and abandoned mines. Density of hibernating bats can range from 300 to 484 bats/square foot. Some caves support over 80,000 bats. Suitable hibernation sites in caves must be draft- free and have a constant winter temperature. After hibernation, Indiana bats migrate to summer roosts, which are generally edges of hardwood forests. During summer, males roost singly or in small groups. Females may roost in groups of up to 100 bats. How do Indiana Bats reproduce? Bats mate in fall before entering caves for hibernation. Females store sperm through winter and become pregnant in spring after hibernation, then migrate to summer areas, where they roost under peeling bark of dead or dying trees to have their young (called pups). These bats have only 1 pup each year. What is the diet of the Indiana Bat? Variety of night-flying aquatic and terrestrial insects along rivers, lakes and in upland areas, such as flies and moths. When was the Indiana Bat first listed as Endangered? By USFWS on March 11, 1967. What is meant by "Endangered"? Endangered species are animals and plants that are in danger of becoming extinct throughout all or a significant portion of their range. How does a species become listed as Endangered or Threatened? The listing process is one of the basic functions performed by USFWS in carrying out its responsibilities under the Endangered Species Act. USFWS has developed a priority system designed to direct its efforts toward the plants and animals in greatest need of protection. In order to list, reclassify, or delist a species, USFWS must follow a strict legal process known as a "rulemaking" procedure. The rule is first proposed in the Federal Register, a US Government publication. After a public comment period, USFWS decides if the rule should be approved, revised, or withdrawn. This process encourages the participation of all interested parties, including the general public. The entire process can take up to a year or longer in unusual circumstances. What does Endangered listing mean? Once a species is listed, all protective measures authorized by the Endangered Species Act apply to the species and its habitat. Such measures may include: protection from any adverse effects of federal activities; restrictions on taking, transporting, or selling a species and authorization for USFWS to develop and carry out recovery plans. Why is the Indiana Bat Endangered? Indiana Bat populations have been declining since early 1960s. The declining numbers were observed at hibernation sites such as caves and abandoned mines, where the bats gather in large numbers. There are several scientific theories as to what factors are contributing to the bats' decline: Human Disturbance - First listed as endangered largely because of their habit of living in very large numbers in only a few caves. This makes the bats extremely vulnerable to disturbance. Significant portion of the population can be affected by just one event. Cave Commercialization and Improper Gating - Any gate or structure placed on the cave or mine that prevents bat access or alters air flow, temperature, humidity, or amount of light is harmful. Low Birth Rate - Because of low reproductive rates (Indiana Bats typically have only 1 young each year) coupled with a potentially high death rate, it may take years to replace lost individuals. What are other possible causes of Indiana Bat decline? The following is speculation that has yet to be proven: Habitat Loss or Degradation - Much of the midwestern forests have been converted to urban and agricultural uses, removing forest habitat from Indiana Bat use. Agricultural Chemicals - Chemicals may kill insects that bats eat. The bats may eat contaminated insects; drink contaminated water, or absorb chemicals when feeding in recently-treated areas. Endangered Species Fact Sheet
Some Bats found in Pennsylvania
|
Bat Links
Endangered Bat links:
Arkansas Game and Fish
Commission:
Indiana
Bat (Myotis sodalis)
Gray Bat (Myotis
griscens)
Ozark Big-Eared
Bat (Plecotus townsendii ingens)
University of Michigan: Endangered Animals in Pennsylvania
Indiana
Bat (Myotis sodalis)
Missouri Coservation Department: Endangered Species Guidesheets
Indiana
Bat (Myotis sodalis)
West Virginia Division of Natural Resources:
Indiana Bat (Myotis
sodalis)
Texas Parks and Wildlife Department:
Mexican long-nosed
bat (Leptonycteris nivalis)
Other Bat links
Bat
Conservation International
California Bat Conservation Fund
Bats4kids
Organization for Bat Conservation
Links to Other Endangered Species Related Sites
Go
to the Endangered Species Home Page
Some information for this page was taken from:
Bats of the United
States
by
Michael J. Harvey
Tennessee
Technological University
J. Scott Atlenbach
University of New Mexico
Troy L. Best
Auburn
University
Why
is it called Indiana Bat?
