Bats of Texas

Illustrated Keys to the Bats of Texas

Illustrated Keys to the Bats ofTexas Two keys have been prepared for the 33 species of bats known to occur in Texas. The first is based on external characters of adult animals. Subadult or juvenile bats usually show the diagnostic characters of the adult, although their pelage color may be slightly different (usually lighter). The best way to distinguish a juvenile from an adult bat is to examine the cartilaginous area in the finger (metacarpal-phalangeal) joints (fig. 9); the larger the area, signifying that the joints have not fused, the younger the bat. After an identification is made using the external key, refer to the account of the species , which provides a more extended description , including additional characters. The distribution maps also provide clues to help verify or question an identification. If a skull is available, it should be examined as a check on the identification made by using external characters. The second key, based on cranial and dental structures, follows the key based on external characters. Both keys are arranged so that there is always a choice between 2 statements (a couplet) about some characteristic of a bat. To identify a bat, use a millimeter ruler or similar instrument to make the required measurements, and select the appropriate alternative from each couplet (1, 2, 3, etc.) in the key. At the end of the statement chosen is a number that indicates the location of the next choice to be made. The process should be repeated until a name instead of a number is given at the end of a line. 54 illustrated keys to the bats of texas figure 9. Wing of Eptesicus fuscus, labeled to show names of external parts and measurements used in the key to Texas bats. The insert drawing is an enlargement of the metacarpal-phalangeal joint in a juvenile (a) and an adult (b) bat. a juvenile b adult ear length forearm length total length hind foot length thumb length metacarpal-phalangeal joint tail length tragus length key to external characters 55 Key to External Characters A millimeter ruler and, in some cases, a hand lens are required. When possible, the characters used in this key have been chosen so that the animal need not be sacri ficed and also can be used with scientifically prepared voucher specimens (see Barbour and Davis 1969 for an explanation of this procedure). Some measurements and features are difficult to verify in voucher specimens because features shrink or deform when they are dry. This is particularly 1. Distinct, upwardly and freely projecting, triangular-shaped nose leaf at end of elongated snout (fig. 10a). . . . . . . . . . . . . . . . . Family Phyllostomidae (in part) 2 Nose leaf absent, indistinct, or modified as lateral ridges or low moundlike structure; snout normal (fig.10b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Tail evident, protruding about 10 mm from dorsal side of interfemoral membrane (fig. 11a); distance from eye to nose about twice the distance from eye to ear (fig. 11c); forearm less than 48 mm. . . . . . . . . . .Choeronycteris mexicana Tail not evident (fig. 11b); eye about midway between nose and ear (fig. 11d); forearm more than 48 mm. . . . . . . . . . . . . . . . . . . . . . . . . . Leptonycteris nivalis 3. Thumb longer than 10 mm; hair straight, lying smoothly, glossy tipped . . . Family Phyllostomidae (subfamily Desmodontinae, vampire bats) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diphylla ecaudata Thumb less than 10 mm; hair slightly woolly, pelage lax, not usually lying smoothly, not glossy tipped . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Prominent grooves and flaps on chin (fig. 12a); tail protruding from dorsal surface of interfemoral membrane (fig. 12b) . . . Family Mormoopidae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mormoops megalophylla No notable grooves or flaps on chin; lumps above nose or wrinkled lips possible; most faces lack even these characteristics; tail extends to or beyond edge of interfemoral membrane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. Tail extends conspicuously beyond free edge of interfemoral membrane (fig. 13a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Family Molossidae 6 Tail extends to or just beyond the free edge of interfemoral membrane . . . . . . . . (fig. 13b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Family Vespertilionidae 9 6. Forearm more than 70 mm; upper lips without deep vertical grooves . . . . . . . . . (fig. 14a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eumops perotis Forearm less than 70 mm; upper lips with deep vertical grooves (fig. 14b) . . . . . . 7 true of the ears, the tragus, (fig. 9) and any elaborate facial features. All measurements (as defined and shown in fig 9) and weights are in millimeters and grams respectively unless stated otherwise. One of the external measurements taken on bats, the length of the forearm, differs from the usual standard measurements taken on small mammals. Forearm length is the best...