bat winged mammal of the order Chiroptera, which includes 900–1,000 species classified in about 200 genera and 17 families. Bats range in size from a wingspread of over 5 ft (150 cm) to a wingspread of less than 2 in. (5 cm). They are found in nearly all parts of the world but are most numerous in the tropics; there are about 39 species in the United States. Most bats are economically valuable because of the large number of insects they consume.

The body of the bat is mouselike and usually covered with fine fur. The face varies greatly from one species to another; many species have complex appendages on the snout and projections, or false ears, in front of the true ears; the ears themselves are often very large and elaborately convoluted. These facial structures are part of the sensory apparatus that emits and receives sound vibrations.

Some bats are solitary, living in caves, crevices, hollow trees, or attics; other species are communal, with thousands or even millions of bats roosting together in a cave or on branches in a section of forest. In some species of communal bats, the entire colony leaves the roost together in the evening and returns together in the morning; in others, individuals come and go at different times. Bats of northern regions migrate, hibernate, or both in winter.

In most species, males and females do not associate except during the mating season. Females of most species bear a single young in the summer of each year. The young are then carried by the mothers for a few days, after which they are left in the roost when not nursing; they begin to fly in a few weeks. The life span of some bats is 20 years in captivity.

Special Characteristics

Bat Flight

Bats are the only mammals capable of true flight, that is, flight powered by muscular movement as distinct from gliding. The wing is a double membrane of skin stretched between the enormously elongated bones of four fingers and extending along the body from the forelimbs to the hind limbs and from there to the tail. The thumb is small, clawed, and free from the membrane. The hind limbs are small and may be rotated in such a way that the knees bend backward rather than forward, as in other mammals; this is presumably an adaptation for takeoff and flight. Bats at rest hang head down, grasping a twig or crevice with their clawed feet; they take off into flight from this position.

Echolocation

Nearly all bats are nocturnal and many live in caves; although they see well, they rely primarily on their highly developed hearing, using echolocation (sonar) to avoid collisions and to capture insects in flight. The bat emits high-pitched sounds (up to 100,000 hertz) that echo from objects it encounters; the echo provides the bat with information about the size, shape, and distance of the object. The rate at which bats emit these squeaks is sometimes as high as 200 per second. Blinded bats easily find their way through complex obstacle courses, but deafness leaves them helpless.

Types of Bats

The bat order is divided on anatomical grounds into two major divisions, or suborders: the Megachiroptera, or fruit bats , found only in the Old World tropics, and the Microchiroptera, or insect-eating bats, with a worldwide distribution. The fruit bats include the largest species of bat, the flying foxes, which may weigh 2 or 3 lbs (.9 to 1.4 kg). Their diet is confined almost entirely to fruit, nectar, and pollen. The insect-eating bats include the smallest bat species. Despite the name, some of these bats live wholly or largely on fruit; a large number eat insects and, in some cases, larger animals. Members of several species catch fish as they skim over water, and the South American vampire bats feed exclusively on blood.

The most common bats of the temperate Northern Hemisphere are the Old World horseshoe bats ( Rhinolophus ), characterized by one or two horseshoe-shaped facial appendages, the cosmopolitan little brown bats ( Myotis ), big brown bats, or serotines ( Eptesicus ), and pipistrelles ( Pipistrellus ). The last three, all represented by species in North America, belong to the plain-nosed bat family (Vespertilionidae), characterized by a lack of appendages on the snout.

There are over a dozen species of Myotis in North America; the common little brown bat, M. lucifugus, is distributed over the entire continent from Alaska and Labrador to the S United States. A colonial bat, it is found in many habitats, including houses. It is about 2 1/2 in. (6.3 cm) long without the tail and weighs about 1/4 oz (7 grams). The North American big brown bat, Eptesicus fuscus, of similar distribution, is about three times as heavy, with a wingspread of 12 in. (30 cm). The little and big brown bats are among the species susceptible to white-nose syndrome, which leads to water loss and emaciation during winter hibernation. Identified in 2006 and caused by the fungus Geomyces destructans, it has been devastating to bat colonies in North America. Large, solitary North American bats of wide distribution are the hoary bat, Lasiurus cinereus, yellow-brown with silver frosting, and the red bat, L. borealis, which is a striking brick-red color. Both have soft, thick fur and roost in trees.

The freetail bats (family Molossidae) are a cosmopolitan group of communal bats characterized by a long tail extending well beyond the end of the tail membrane. Among them are the guano bats ( Tadarida ), which live in enormous colonies. Their excrement, called guano , accumulates in great quantities in their roosting places and is commercially valuable as fertilizer. Most New World freetail bats are tropical, but several are found in the S United States. One of these, the Mexican freetail bat ( Tadarida brasiliensis ), is noted for its colonies in the Carlsbad Caverns of New Mexico, numbering an estimated 250,000 to 500,000 individuals. When these bats leave the caves together it takes about 20 min for the entire column to make its exit. This family also includes the mastiff bats ( Eumops ), largest of the North American bats, with a wingspread of 18 in. (46 cm).

Classification

Bats are classified in the phylum Chordata , subphylum Vertebrata, class Mammalia, order Chiroptera.

Bibliography

See R. W. Barbour and W. H. Davis, Bats of America (1969); W. A. Wimsatt, ed., Biology of Bats (2 vol., 1970).

bat¹ / bat/ • n. an implement with a handle and a solid surface, usually of wood, used for hitting the ball in games such as baseball, cricket, and table tennis. • v. (bat·ted , bat·ting ) 1. [intr.] (of a team or a player in sports such as baseball) take in turns the role of hitting rather than fielding: Ruth came to bat in the fifth inning. 2. [tr.] hit at (someone or something) with the palm of one's hand: he batted the flies away. PHRASES: right off the bat at the very beginning.PHRASAL VERBS: bat something around inf. discuss an idea or proposal casually or idly. go to bat for inf. defend the interests of; support: his willingness to go to bat for his employees. bat² • n. a mainly nocturnal mammal (order Chiroptera) capable of sustained flight, with membranous wings that extend between the fingers and connecting the forelimbs to the body and the hindlimbs to the tail. PHRASES: have bats in the (or one's) belfry inf. be eccentric or crazy. like a bat out of hell inf. very fast and wildly. bat³ • v. (bat·ted , bat·ting ) [tr.] flutter one's eyelashes, typically in a flirtatious manner: she batted her long dark eyelashes at him. PHRASES: not bat (or without batting) an eyelid (or eye) inf. show (or showing) no reaction: she paid the bill without batting an eyelid.

bat Only mammal that has true flight (although a few mammals can glide). Bats are nocturnal and found in all tropical and temperate regions. Most are brown, grey, or black. A bat's wing is formed by a sheet of skin stretched over a frame of greatly elongated bones. Bats are able to navigate in complete darkness by means of a kind of sonar, which uses echoes of the bat's own supersonic squeaks to locate obstacles and prey. Many bats live largely on insects, some are carnivorous, some drink blood, some live on nectar and pollen, and one group – flying foxes – subsist on fruit. Most are small, although they range in wingspan from 25cm–147cm (10–58in). The 178 genera of bats make up the order Chiroptera.

bat in poetic use, bats are often associated with the coming of night and darkness. They have also a sinister association with vampires, notably in the tradition established by Bram Stoker in Dracula (1897). The bat is also taken as a type of blind creature, as in blind of Chancery.
have bats in the belfry be crazy or eccentric; the phrase is recorded from the early 20th century, and the colloquial use of ‘bats’ to mean mad derives from this.
like a bat out of hell (moving) extremely fast; recorded from the 1920s.

Bat

There is an Oriental belief that the bat is specially adapted to occult uses. In the Tyrol, there is a folklore belief that the man who wears the left eye of a bat may become invisible, and in Hesse, he who wears the heart of a bat tied to his arm with red thread will always be lucky at cards.

bat1 club, stout stick OE.; implement for striking ball in games XVIII. Late OE. batt ‘clava’ some uses poss. from (O)F. batte (f. battre beat).
Hence, or directly — (O)F. battre, bat vb. XV; in the sense ‘wink (the eyelids)’ perh. a var. of BATE.

bat2 mouse-like winged quadruped. XVI. alt. of ME. bakke (till XVII in gen. use) — Scand. word repr. in OSw. aptan-, nattbacka evening or night bat.

bat See CHIROPTERA.

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