Phyllostomidae—Leaf-nosed Bats // Molossidae—Free-tailed Bats // Vespertilionidae—Vespertilionid Bats
The Chiroptera is one of only four groups of organisms that have achieved true flight (the others being the extinct Pterosaurs, the birds, and the insects). Each of the four groups have evolved flight independently by different mechanisms. The word "chiroptera" translates from the Latin as "hand wing". This is an apt description, since a major adaptation is a hugely enlarged hand. As can be seen in Fig. 1, the hand may more or less equal the upper arm plus forearm in length. Except for the thumb, the metacarpals and digits are joined by a membrane (the chiropatagium) consisting of skin, connective and nervous tissue, etc. The membrane also extends to other parts of the body, especially to the legs, but also generally including a section in front of the elbow and often between legs and tail. Flattened body and, in some species, huge ears also may play a part in providing lift during flight.
Fig. 1. Flight membranes and skeletal support system of a myotis bat (dried specimen). UTEP Biodiversity Collections photo.
Because of crepuscular and nocturnal habits of bats, people generally don't realize the diversity within the order. The number of species (a bit over 1100 according to Wilson and Reeder ) is surpassed only by the rodents, and various kinds of bats are adapted to feed on insects and other arthropods, nectar and pollen, fruit, blood, fish, or small mammals. Most taxa are tropical, but temperate zones support a diverse chiropteran fauna.
The somewhat flitting flight commonly observed at twilight leads some to believe that bats are clumsy fliers. Nothing could be further from the truth, and bats rival birds in their flying abilities. In addition to mastery of flight, the largest subgroup of bats (the suborder Microchiroptera) employ echolocation. That is, ultrasonic emissions from the mouth or nose echo off of the environment, allowing the bat to "visualize" its surroundings. Insectivorous forms are able to accurately judge the size, distance, direction and speed of travel, and nature of the surface (hard as in beetles, soft as in moths, etc.) of their prey. Appropriate prey then can be taken on the wing. The great variety in facial structure and in ear size and shape generally has to do with the requirements of the particular species in terms of echolocation. Feeding requirements, of course, also may shape the head characteristics; nectar feeders, for example, generally have elongated snouts.
Fig. 2. Colony of Mexican Free-tailed Bats (Tadarida brasiliensis). The dark patch on the cave ceiling is made up of several thousand bats, a few of which can be seen in flight closer to the camera. U-Bar Cave, Hidalgo Co., NM.
Many species (though not all, by any means) utilize caves for daytime roosts, for maternity roosts, and for hibernation. Many people are aware that colonies of Mexican Free-tailed Bats (Tadarida brasiliensis) have had maternity colonies numbering in the millions of individuals, such as at Carlsbad Caverns. From the viewpoint of the paleontologist, caves often are treasure troves of bat remains, whereas bats in open sites are almost beyond rare.
Wilson and Reeder 2005.
Last Update: 11 Mar 2013