Bats Essay, Research Paper

INTRODUCTIONThere is an abundant amount of animal species in the world. They all have adapted and evolved to survive in their surroundings. Some have grown fins, others legs, and still others wings. One of the animals that has grown wings is the bat. The bat is a truly great creature. It has all the characteristics of mammals while also possessing the skill of a bird in flight.

There are more than 800 species of bats in the world. They are of many different sizes, shapes, and lifestyles. They live all over the world and have drawn the curiosity of millions. Bats also have the unique feature of echolocation that it uses to catch insects. Though other mammals, like the flying squirrel seem to fly but actually glide, the bat is the only mammal that can truly fly (Lauber 1968).

A Bat’s BodyDue to the great variety of species of bats some characteristics vary greatly, but the Little Brown Bat is a good example of a common bat. It has fur on the body, large naked ears, the rear legs have claws, a tail membrane, and it has the most distinguishing feature of a bat, wings (Lauber 1968). The upper arm of the bat is short while the forearm is very long (Fig. 1). The wrist is very small and from it comes the thumb and the four longer fingers. The thumb is short and used for climbing or walking. The fingers are long and thin. Interlocking the fingers is the wing. This arrangement of having the fingers in the wing gives the bat amazing flight maneuverability (Honders 1975). These bones look similar to a human hand. They are connected by rubbery skin to the bat’s body enveloping all the fingers but the thumb (Anonymous 1990).

EcholocationBats have a “sixth sense” called echolocation. This was first proved by Donald Griffin. Bats produce ultrasonic sound waves and then use the echo of the returning sound to sense the world around them and in particularly to catch insects. These sounds are usually out of the humans range of hearing (Fellman 1993). This system is similar to that of dolphins. The sound is in the form of clicks that increase as the bat gets closer to the insect or whatever it is tracking (Anonymous 1990).

Unlike humans, most insects can hear the bat’s echolocation sounds. David D. Yager of the University of Maryland has found that the praying mantis has used this to its advantage. When being pursued by a bat the mantis can hear the clicks of the bat behind it and to avoid being eaten goes into a series of evasive maneuvers. First they extend their fore limbs, then they extend their abdomens which stop them. Then they go into a dive achieving a pace twice their usual speed and if still being pursued will crash into the ground to avoid being eaten. This and other insects also use hearing to their advantage (Amato 1991). Moths also do amazing maneuvers in attempts of escape, similar to the mantis. Tiger moths even make their own ultrasonic clicks. It is not known whether these are to startle the bat or to warn it that the moth is distasteful (Fellman 1993).

Despite the insects great efforts to foil the bat’s sonar the bat still catches its prey more than fifty percent of the time (Fellman 1993). Some bats even have different frequencies than insects can hear. The competition between insects and bats will go on forever because they will counter each other’s counter measures by evolving new strategies, and as James Fullard said “Evolution never stops.”

HIBERNATION AND MIGRATIONThe food of bat usually becomes scarce during winter months so some bats hibernate while others migrate (Honders 1975 and Bourliere 1995). When bats migrate they usually move from the South to far North during the summer and they return during the fall. Bats that hibernate prepare for the winter by getting fat in autumn. Then they fall into a sleep more extreme than their normal daily sleep. As in most animals, when hibernating their major bodily functions, such as heart-rate and breathing, are suppressed greatly. Bats are known to interrupt their hibernation because they have been seen in the winter.

Disturbing bats during hibernation can be very destructive (Pistorius 1994). This is because the bats have a limited supply of energy. The energy used when the bat is awake is huge compared to that when it is hibernating. Bats arise on occasion anyway to groom, or sometimes take a flight outside, and even to move to colder places, where they can survive with lower metabolism and save energy. Repeated awakenings can result in starvation during the late winter from lack of energy stores. In an extreme case in Kentucky, during the 1960’s where a cave was a tourist attraction, the population of 100,000 bats starved to death after being awakened on several occasions.

REPRODUCTION Bats have internal fertilization and give birth to highly matured young like humans (Lauber 1968, Honders 1975, and Ezzel 1992). Most bats only have one baby a year. The bats mate in the roost and have little or no courtship. The pregnant mothers form separate nursing colonies from the others. Some species like the Mexican free-tailed bat, who migrate immediately after mating, produce a secretion that preserves the male’s sperm until they reach their new roost.

When their baby is being born the mother hangs by her thumbs to a tree branch. Its tail membrane acts as a cradle and the baby is born into it tail first. Then the mother hangs by one wing and cleans the baby with the other. It is then attached to the mother’s teat where it will hold on during flight. In some species the baby is left at the roost when the mother is hunting, in others the baby is taken along. In the species that carry their young eventually the baby grows too big for the mother and is left in the roost. The bat then learns to fly and hunt its prey by itself (Lauber 1968).

SPECIALIZED BATSSome bats have developed special ways of adapting to their surroundings. Though most bats eat insects, some feed on fruit, nectar, small vertebrates, fish, and blood (Bourliere 1995). The bats that eat fruit help disperse seeds by eating and then dropping the seeds in their droppings during flight. Those that drink nectar act like hummingbirds pollinating flowers (Anonymous 1991). Bats that eat small vertebrates along with insects and fruit are often called false vampires. These bats eat lizards, tree frogs, birds, rodents, and smaller bats. They kill their prey by using their strong jaws and teeth to break their neck. These bats have only about a two foot wingspan so their prey tends to be small. Bats that catch fish fly just above the water and catch the fish with its hind feet and use its sharp claws to hold it. It then maneuvers the fish to kill it by biting it (Novick 1973).

The most famous of bats is probably the vampire. The vampire bat drinks the blood of large vertebrates when they are asleep. To help in doing this they have developed large incisors, a specialized tongue, and specialized saliva to prevent blood from clotting. They are also able to move quickly on the ground in case of their prey waking up and it is too full of blood to fly away (Honders 1975).

MYTHSThere are many misconceptions about bats (Anonymous 1990). People think they are all dangerous because they carry rabies. Less than one percent of all bats is infected with rabies. Some people think they become caught in people’s hair, but this is also untrue. Other people think lots of bats drink blood but this is also untrue, only three species of bats drink blood. These prefer cattle blood and only live in Latin America.

Bats are actual quite helpful to humans (Van Dyke 1994). Bats are important to many plants in the United States because they help pollinate flowers. Most bats eat insects, this is extremely helpful to humans. They help keep bug populations low. Some bats, such as the little brown bat, can consume about 600 mosquitoes in an hour. Bats also keep the population down of other potential pests such as leafhoppers, cucumber beetles, and June bugs.

Despite bats being helpful they can still be dangerous under certain conditions (Anonymous 1988). Bat droppings, or guano, are known to have spores and fungus in them that cause Histoplasmosis, a lung infection, and other diseases. Rabid bats can also be a threat because if one attacks the victim can easily be infected with rabies. If anyone ever has to handle a bat always wear gloves to prevent bites.

Bats are a good example of how an animal can evolve to have amazing abilities. Bats have evolved to fly, use echolocation, hibernate, sleep in the day, hang by their feet, and many other things that individual species have developed. Some large bats, called megabats, are even thought by some scientists to be closely related to primates because of their similar brain tissue. Bats are highly evolved animals that have amazing characteristics (Gibbons 1992 and Bailey et al. 1992).

LITERATURE CITEDAnonymous. 1988. Bats. Pamphlet distributed by Missouri Department of Health. pp 1-2.

Anonymous. 1990. Bats In Connecticut. Pamphlet from Connecticut Department of Environmental Protection. pp 1-8.

Anonymous. 1991. Warning From Bat Conservation International. Pamphlet from Animal Welfare Institution. pp 1.

Amato, I. 1991. “Praying Mantises Play Top Gun”. Science 252: 781

Bailey, W. et al. 1992. “Rejection Of The Flying Primate Hypothesis”. Science 256: 86-89

Bourliere, F. 1995. Mammals of The World. Alfred A. Knopf, New York. pp 190-196

Ezzel, C. 1992. “Cave Creatures”. Science News 141: 88-90

Fellman, B. 1993. “Guess Who’s Coming to Dinner”. National Wildlife 31: 42-45

Gibbons, A. 1992. “Is Flying Primate Hypothesis Headed for a Crash Landing?”. Science 256: 34

Honders, J. 1975. The World of Mammals. Peebles Press, New York. pp 22-23.

Lauber, P. 1968. Bats Wings in the Night. Random House, New York. pp 1-15

Novick, A. 1973. “Bats Aren’t All Bad”. National Geographic 143: 615- 627.

Pistoris, A. 1994. “Forever Protected”. Harrowsmith Country Life 28-35.

Van Dyke, L. 1994. “Batting Down Bugs”. Sierra Magazine 36-68