Bats are somewhat difficult to study because of
their secretive, nocturnal habits and their
flight capabilities. Although well over nine hundred
species have been identified and catalogued,
additional species have since been discovered,
primarily from the South American rain forests.
New ones remain to be discovered, and the classification
of bats continues to be improved.
Bats are the most widely distributed kind of
terrestrial mammal. They are found from Alaska
to the tip of Argentina and from near the Arctic
Circle to South Africa. They occur widely through
the tropical regions and in the temperate zones.
Physical Characteristics of Bats
Although bats range in size from tiny hog-nosed bats that weigh less than a penny to flying foxes whose wing spans exceed five feet, the majority of bats tend to be small. Despite variation in size, all species of bat share the same body form, with certain similarities in fur and skin, wings, teeth, reproductive system and patterns, and visual and hearing systems. The bat's skin is black or dark grayish brown in color, with tiny transparent hairs on the membrane surface. While most bats have small eyes, perhaps encouraging the misconception that bats are blind, their auditory system is developed to an extraordinary degree. Of the bats who feed on animals, some feed on insects and whole animals; vampire bats, which occur from Mexico to Argentina, feed only on the blood. Plant-eating bats feed on fruit and flowers. Female bats give birth at the roost site, frequently while hanging upside down. Bat young are born in a breech presentation and are helpless until they are large enough to fly. Brown bats reach adult size and begin to fly at three to four weeks of age.
The Behavior of Bats
The major behavioral pattern of bats is nocturnal activity. During nocturnal flight, bats are protected from being visually spotted by predators and from exposure to the sun and to high temperatures, which promote heat absorption and the loss of body water necessary for temperature regulation. Bats routinely seek shelter during the daylight hours. Caves provide protection from the sun and predators and allow bats to conserve energy under consistent temperature and moisture conditions. Bats also shelter in tree cavities, crevices, buildings, and trees. While tropical bats are active all year round, bats in temperate regions hibernate during the winter in order to accommodate the diminished food supply. Most hibernating bats spend the summer feeding heavily on insects, building up enough fat to provide energy during hibernation. During hibernation, the bat allows its body temperature to fall to that of the surrounding air, and as its pulse and breathing rates slow down, it essentially enters a state of suspended animation. The sole characteristic that sets bats apart from other mammals is flight. Some bats fly high, fast, and far, while others fly more slowly, maneuvering around obstacles, catching their prey on the wing, or plucking it from the ground. Soaring is uncommon in bats, as is swift flight in comparison with birds. Bats fly in flocks sometimes numbering in the thousands, a precaution against predators. Microchiropteran bats use echolocation, a pulse system of highfrequency sounds and their echoes, to navigate and to locate food. Bats emit sound, then receive and analyze the data from the returning echoes which provide information on direction and distance to the target. Best suited to short distances, echolocation is so accurate that some bats appear able to distinguish among individual species of insects. Bats are allies of human beings in controlling the insect population. Most species of bats found in the United States feed on beetles, moths, and crickets, many of which destroy vegetation and are damaging to agricultural interests. Recent studies also suggest important uses for anticoagulent compounds, found in vampire bats' saliva, that hinder the clotting of blood.
Order: Chiroptera (bats)
Suborders: Megachiroptera (flying foxes), Microchiroptera (bats)
Families: Pteropopidae (flying foxes, forty-four genera, 173 species); Rhinopomatidae (mouse-tailed bats, one genus, three species); Emballonuridae (sheath-tailed bats, thirteen genera, fifty species); Craseonycteridae (hog-nosed bats); Nycteridae (slit-faced bats, one genus, eleven species); Megadermatidae (false vampire bats, four genera, five species); Rhinolophidae( horseshoe bats, one genus, sixty-nine species); Hipposideridae (leaf-nosed bats, nine genera, sixty-one species); Mormoopidae (leaf-chinned bats, two genera, eight species); Noctilionidae (bulldog bats, one genus, two species); Mystacinidae (short-tailed bats, one genus, two species); Phyllostomidae (spear-nosed bats, forty-seven genera, 140 species); Desmodontinae (vampire bats, three genera, three species); Natalidae (funnel-eared bats, one genus, eight species); Furipteridae (thumbless bats, two genera, two species; Thyropteridae (disk-winged bats, one genus, two species); Myzopodidae (sucker-footed bats);Vespertilonidae (common or vesper bats, forty-two genera, 319 species); Molossidae (free-tailed bats, twelve genera, ninety-one species)
Geographical location: Every continent except Antarctica
Habitat: Mostly forests and deserts; some grasslands
Gestational period: Three to ten months, with delayed implantation
Life span: Generally three to five years; up to thirty years in captivity Special anatomy: Head, body, tail, two wings, each supported by upper arm, forearm, hand; knee joints bend backward enabling the bat to hang upside down and still be ready to take flight easily
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