BATS

NUISANCE OR NECESSITY
by Angela Marshall
 
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Bats have played an essential role in the evolution of nature's checks and balances for a very long time and their loss today could compromise the health and the stability of our environment. The usefulness and resourcefulness of bats are being ignored by our society because of myths and legends which is resulting in a disservice in improving our environment. 

The history and origin of bats is a long and undecided one. Bat fossils have been found that date back approxiatemately 50 million years but bats from today still resemble bats from then. 

Debate has been triggered whether bats have evolved from a type of flying fox, squirrel, flying lemurs or shrew like creatures. Flying lemurs share a unique brain orginization but bats habitats are closest to that of flying foxes however most scientists point to shrew like creatures as their ancestors. 

Bats are placed in a group of their own (from other mammals) the Chiroptera which means hand wing. In the Chiroptera group of mammals there are two types of Chiroptera in which all living bat species fit. The Megachiroptera are commonly referred to as flying foxes (because of their fox like faces) and are only found in the Old World Tropics. The Microchiroptera are highly varied in apperance and are found all over the world. 

Myths and legends that bats are nasty creatures that kill people by sucking out their blood and turning into monsters have led most people to fear and destroy these tiny creatures. In western society, mentioning bats tends to conjure up images of bloodthirsty vampires, draughty dark castles and evil spirits. In much of the world they are treated as harbingers of evil, beasts that deliberately tangle themselves in long hair and consort with supernatural beings such as werewolves and vampires. They are accused of stealing bacon and of being blind. However bats do not try to tangle themselves in people's hair, they do not steal bacon (most bats don't like bacon according to scientists all over the world that laugh at the strange rumour), nor are they blind. 

A visit to the National Bat Conservatory (the Rockville, M.D. division), I discovered a few things. Bats have a tendency to get tangled in a person's hair because they think it's a nest most of the time, and when they try to land on a person's head they accidently get their tiny little claws tangled in the hair and it scares them. Bats are very shy creatures that can be very friendly; even trained as pets. They are warm, soft and furry; not slimy or scaley or cold. When they are happy, they purr like cats. When bats are trapped inside a house and flying around, chances are, they are lost and can't find an exit, so if this ever happens, open a window, don't seal off their exit, and try not to go swinging things at it because it's probably more frieghtened than you are. Be very calm if you can, and give time to find it's way out. 

The popular misconception that bats are dirty and dangerous has led to feeling of distrust and hostility in many parts of the world. Light is commonly used to repel bats at night. Livestock owners sometimes suspend various objects which swing above cattle in night breezes to frighten bats. Some Venezuelan cattlemen claim that a plant called "sabilla" is successfully used to drive away vampire bats; they also claim that pigeons repel bats and pigeon roosts have been establised. Smoke and noise are commonly used to flush bats from roosts. Fitter (1968) reported that more than 700 Brazilian bat caves and certain Panamanian caves were destroyed by dynamite, killing vampires and other species of bats that occupied the caves. Spiny branches of cactus suspended from ceilings in stables and dwellings sometime entangle bats. Even an elaborate network was installed in some Brazilian caves to electrocute bats. Poisonous gas and flame throwers was a common method for killing bats in Africa up until the late 1960's. Abello Fernadez reported success in destroying a colony of bats by infecting them with a local strain of Newcastle disease that had caused a great loss in poultry in the area. The colony was said to have consisted of 5000 vampire bats. 

Poisoning bats with pesticides is the most common means of destruction. Hundreds of bats have been killed by spraying DDT. In South America, organophosphorous compound was discharched into caves by the Antirabies Service destroying over 900,000 bats annually from 1984 to 1987. 

Unnessary arousal of hibernating bats due to the presence of people is another major factor of bat population decline. Exits are blocked and clubs and firearms are used to kill bats in their roosts. Housing developments have boomed in North America in areas causing bats to evacuate their homes. 

Little reseach has been done on bats contributing to diseases by way of bacteria. Two types of salmonella has been reported by Klite (1965) to be pathogenic to man from feces removed from Panama bats. Two types of Shigella (Bacillary Dysentery) was isolated from one of 2112 bats tested in Colombia (Arat et al, 1968). Pasteurella (Pseudotuberculosis) was reported by McDiarnid (1962)in England and cited experimental infections have taken place in Africa and Italy. Mycobacterium (Tuberculosis and Leprosy) have caused deaths in Indian fruit bats held captive in England in the 1930's however reports of such problems today are not documented. The source of infection for the bats was unknown. Bartonella and Grahamella (Bartnellosis) has been documented in Brazil but no form of this species has been reported pathogenic to man. Leptospira (Leptospirosis) has been reported many times over in bats mainly in Australia but no evidence links a transferral to man. Borella (Relapsing Fever) has been cited in bats from Europe, Africa, South America, and the United States from 1927 to 1968 however, when C.M. Johnson attempted to transmit the disease from bat to pig in some lengthy experinments in 1936, he was unsuccessful. 

Vampire bats are true parasites of man and domestic animals according Wimsatt and Guerriere. Blood loss caused by vampire bats has led to debilitation in humans and livestock and usually results in the death of poultry. Wimsatt and Guerrriere have noted in their studies that wild vampire bats may drink on the average 20 ml of blood per day. A single bat thus consume 7.3 liters (15 pints) per year. A moderate sized colony of vampires consisting of 100 adult individuals would drain local livestock approxiatemately 730 liters of blood each year. 

In mexico vampire bats usually bite humans on the cheeks over the zygoma and presumably scars result. They commonly bite the nipples of cows, causing tissue sloughing and obliteration of the ducts making the animals unproductive and eventually die of lack of nourishment. 

The wound created by a vampire's bite according to Darwin interferes with the use of saddles on horses and provides an entry portal for various microbial pathogens and screw worms. 

Vampire bats have been found infected with various agents of disease and in some instances these bats are insrumental in transmitting them. The most common viruses are foot and mouth disease virus and yellow fever virus but the one that bats are feared the most is rabies. Vampire bats have bitten leprosy victims and might spread that disease and it is not inconceivable that they may spread such diseases as anthrax, blackleg, hog cholera, glanders, mange, and others. 

From medicines to fossil fuels bats have an can contribute to our society if more people could invest a positive interest in protecting bats throughout the world. Hibernation or hypothermia increases the ressistance of the host to various viral, bacterial, protozoan and metazoan parasites (Kayser). Bats are of special interest in studies of this nature because as mammals they are more likely to be susceptible to diseases of man than cold blooded creatures, yet unlike other mammalian hibernators, many bats can be quickly induced at any season into a metabolic state resembling hibernation. In these states of hibernation bats were shown to delay the development of Venezuelan equine encephalitis (Corristan 1958), Japanese Bencephalitis and St. Louis encephalitis (Sulkin 1966), tickborne viral infection (Nosek 1961), and Coxsackie B 3 viral infection (Dempster 1961) producing little pathology. Hypothermia at the time of inoculation may have prevented establishment of rabies viral infections in bats (Sadler and Endright 1959; Sulkin 1960). Ammonia has been noted to accumulate in certain bat roosts with concentrations as high as parts per million, which is 50 times the maximum concentration endurable by man for 1 hour of exposure. Observations suggested that ammonia decreased the metabolic rate of Macrotus waterhousii. Carbon Dioxide concentrations are high in some bat roosts, as high as over 50 times the usual concentration. This has shown an extraordinary resistence of Myotis to anoxia. The transilluminated bat wing is an excellent method for observing circulatory and other phonomena (Nicoll and Webb). Studies of the toxicity of alcohol and alcohol drug combinations investigating wing vessel responses have proven successful in discovering complications in humans in this area. Studies in skeletal muscle regeneration concluded that satellite cells transform into myblasts that increase in number and ultimately form new muscle fibers. These studies have been used to study regeneration of damaged nerves in humans. Studies in which melanocytes could be observed in the wing membrane muscles have been used to study hormonal alteration and irradiation. Bats have even been used in studies of cigarette smoke on vasomotion in arterioles of wing membranes so that scientist could see with much ease what it does to humans. In addition to being used in epidemiological studies of diseases, bats may prove useful in several other areas of medical research: (1) Vaccine development. (2) Space biology, because of bat's abilities to tolerate temperature extremes and various gases. (3) As experinmental animals in other stressful environments. (4) The use of hypothermia, hyperthermia, or various gases in the prevention or therapy of diseases caused by viral, rickettsial, bacterial, mycotic, and metazoan parasites. (5) The use of hypothermia in the prevention or therapy of intoxications or radiation pathology. (6) Mechanisms permitting survival in extremes of population congestion. (7) The detection of chlorinated hydrocarbons. (8) The transiluminated wing of the living bat should find additional utilization in the gross and microscopic observation of physiological or pathological phenomena. (9) As a bioholographic model, the bat may enable disclosure of natural methods of information processing and storage in the brain and how these processes may be influenced. 

Knowledge gained from studies of echolocation in bats has been used to make devices that perform a similar function for blind people. The ablilty of bats that perceive objects by sound exceed conventional echolocation because they can distinguish between objects of different shapes. Greguss reported that the bioholographic method (memory data may be stored in holographic form) may not be restricted to bats and that it may function in humans. 

Like most mammals, bats can contract rabies; however it is a common misconception that most bats are rabid. This impression stems from early studies that seemed to show that unlike other animals, bats could contract rabies and transmit the disease over long periods of time and not show any signs of illness themselves. The presumption that they were asymptomatic carriers of rabies received worldwide publicity and quickly became a fact in everyone's mind. Over 20 years of research now shows that less than a half of 1 percent of bats contract rabies which is no higher than that seen in other animals, but unlike dogs and cats rabid bats seldom become aggressive. 

Guano can be a major resource in our world but has been ignored over the past 70 years. Guano and guano enriched soil have been used throughout warm ares of the world as sources of saltpeter for the production of gunpowder. Bat guano is still a valuable source of organic fertilizer in many parts of the world. Guano can even be used for fossil fuels to run car engines. 

Third world countries use dangerous pesticides to kill insects that spread disease not realizing that the very same bats that they kill could one day be controlling the population of harmful insects. It is evident that insectivorous bats consume enormous numbers of anthropods. R.B. Davis noted that capturing a bat returning to it's cave in Texas it's stomach contents weighed 1 gm more than on it's departure earlier. Taking this as the nightly consumption of insects, scientists, extrapolated to a population of 50 million bats feeding an average of 120 nights per vernal cycle in Texas and obtained a total of 6600 tons of insects per year in Texas. Gould (1955) found that some adult bats captured insects at an estimated rate of up to 500 anthropods per hour feeding mostly from moths, small flies and mosquitoes. Ross (1967) did a remarkable study on the food habits of insectivorous bats discovering two methods bats capture their prey: (1) Filter feeding whereby dense groups of prey, possibly found by echolocation are attacked in flight; (2)individual pursuit, also possibly found by echolocation, whereby individual insects are approached then attacked from the rear. In Ross's studies size had a major factor and bats that preferred the filter feeding method usually injested smaller insects. In his conclusions, Ross stated that the apparant preference of different bat species for particular groups of arthropods provides encouragement that bats exert some control over these arthopods. Thus, one species of bat may keep down numbers of gnats and mosquitoes, whereas another species of bat may control moths or beetles. The incident at Eagle Creak Cave were there was over a 99.9 percent decline in population in a three year span ment more than 350,000 pounds of insects went uneaten nightly, inexorably upsetting nature's balance. 

The removal of bats from the wild for scientific and educational purposes, as well as for food and and just to clear land for more space for people has to be controled. By 1978, two North American species, Grey and Indiana Bats were listed as officially endangered because of human population growth. In 1963, the world's largest known bat colony, close to 30 million Mexican free tails lived in Eagle Creek, Arizona. In just six years their numbers were reduced to 30,000 which was a 99.9 percent decline. Major population losses are documented on all continents. Flying foxes, have recently become extinct without being declared endangered. 

Although bats have a reputation as far as diseases go that is very hard to fight the work that they have and can help us achieve in the medical field is too great to ignore. Along with the endangerment and extinction of some species of bats, we should look at the cruel and unnessary methods of using and abusing these creatures and find alternative methods for controling them. Negative attitudes must be replaced with an understanding of the ecological, economic, and scientific value of bats. This goal can be achieved through education. 



Bibliography: 

Dalquest, W.W. "Natural history of the Vampire bats of eastern Mexico." American Midland Nature, 1955, 53, 7987 

Darwin, Charles R., "Journal of Researches into the Natural History and Geology of the Countries Visited during the Voyage of the H.M.S. Beagle," Routledge, England. 1891 

Fenton, Brock, "Just Bats." Canada: University of Toronto Press, 1983. 

Geluso, Kenneth, N., J. Scott Altenbach, Ronal C. Kerbo, "Bats of Carlsbad Caverns National Park." Carlsbad, 

New Mexico: Carlsbad Caverns Natural History Association, 1987 

Greguss, P., "Bioholography," Nature. 1968, 219 

Nowak, Ronald M. "Walker's Bats of the World." Baltimore, M.D.: The Johns Hopkins University Press, 1994. 

Turner, Dennis C. "The Vampire Bat." Baltimore, Maryland: The Johns Hopkins University Press, 1975. 

Tuttle, Merlin D. "America's Neighborhood Bat's." Austin, Texas: The University of Texas Press, 1988. 

Wimsatt, William A. "Biology of Bats Volume II." New York, New York: Academic Press, 1970. 

Yalden, D.W., P.A. Morris. "The Lives of Bats." New York, New York: Quadrangle/ The New York Times Book Company , 1975. 

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This page copyright © 1997 Angela Marshall.