Bats . . . .

This ability, coupled with the ability to navigate at night by using a system of acoustic orientation (echolocation), has made the bats a highly diverse and populous order.

Locomotion

Flight is the primary mode of locomotion in all bats, although the flight styles vary. Some groups (the free-tailed bats, for example) are adapted for flight in open spaces and high altitudes. They have long, narrow wings, swift flight, and a large turning radius. Slit-faced bats (Nycteridae), false vampire bats (Megadermatidae), and others are adapted for hovering as they pick prey off vegetation or feed on flowers. These bats have short, broad wings, slow flight, and a small turning radius. Some bats take flight easily from the ground: members of the genus Macrotus do so simply by flapping, while vampire bats (Desmodus) leap into the air and then spread their wings and fly. The free-tails, however, roost well above the ground because, upon takeoff, they fall before becoming airborne.

Though flight speeds in the wild are hard to measure, four vesper bat species, carefully observed, have been timed on average at 18.7 to 33.3 km (11.7 to 20.8 miles) per hour. In flight the posture of each of the four fingers incorporated into the wing is under precise and individual control. Finger and arm postures, which determine the shape, extension, and angle of the wings, govern such actions as turning, diving, landing, and hovering. Except when interrupted by insect catches or obstacles, bat flight paths are straight. Insects may be pursued and captured at a rate of up to two per second; during each catch the flight path is interrupted and thus appears erratic.

In many cases there is little locomotion other than flight. Bats that hang in caves may move across the ceiling by shifting their toehold, one foot at a time. A few genera, especially among the Old World fruit bats (family Pteropodidae), may crawl along branches in a slothlike posture, using their thumb claws as well as their feet. The sheath-tailed bats (family Emballonuridae) and mouse-tailed bats (family Rhinopomatidae) hang on vertical surfaces suspended by their hind claws but with their thumbs and wrists propped against the surface. In this orientation they can scramble rapidly up or down and forward or backward, as well as sideways.

Bats of many families walk or crawl on either horizontal or vertical surfaces, using hind feet, wrists, and thumbs. Many move freely either backward or forward, a convenience for entering and leaving crevices. The vampire bats may also leap from roost to roost. The disk-winged bats (family Thyropteridae) and sucker-footed bat (one species, family Myzopodidae), as well as the bamboo bats (Tylonycteris), have specialized wrist and sole pads for moving along and roosting on the smooth surface of leaves or bamboo stalks. Bats are not known to swim in nature except, perhaps, by accident. When they do fall into water, however, they generally swim competently.