Aberrant Coloration in Tadarida Mexicana

Abstract

There seem to be no records of color aberrations in the genus Tadarida. Allen (1940) stated that both melanism and albinism are rare in bats, then cited the few instances known to him. Setzer (1950) listed nine genera with known cases of albinism in his brief review of the subject. To this list may be added the Mexican free-tailed bat, Tadarida mexicana, on the basis of numerous instances of albinism reported herewith. According to Anthony (1928) the color of T. mexicana is uniform warm brown, near bister brown, ------underparts lighter than upperparts and with more yellow. Other authors agree with this description, adding that the hair of the back and neck is white at the base. On several occasions between 1947 and 1952 the writer has visited two of the many gypsum caves, in western Oklahoma, that harbor colonies of thesie bats. One of these is in northern Woodward County among the bluffs on the west side of Bear Creek (SWI/4 S22, T26N, R19W). The other is in western Major County near Ewers Creek (NWI4 ST, T26N, R19W). In both of these caves a large percentage of the population exhibits some degree of albinism. Ignoring those individuals whose albinism is limited to a very few scattered white or whitish hairs, the most frequent variant consists of a type designated for convenience as chin-whiskers. In these individuals the underside of the chin and throat is white. The shape of the white area is variable, but is usually in the form of two streaks diverging posteriorly from near the tip of the chin. The effect is vaguely reminiscent of the beard of the late Emperor Franz-Josef of Austria (plate 1). Deviations from this pattern include asymmetry of the streaks, absence of either one of them, or the presence of a median streak between the other two. Forty-nine of the 79 specimens from the Woodward County cave examined were found to possess this trait, while it was found in 9 of 18 from the Major County colony. Of much less frequent occurrence at either site are bats with large irregular areas of white hair, or with the color of the hair over the entire body dilute (plate 1). Five of these have been taken from Woodward County cave, one from the cave in Major County. A second individual with extremely bold markings was seen in a crevice at the latter site, but eluded capture. The white areas are quite irregular in shape and size, but are nearly always situated on the top of the head or across the shoulders. One specimen has two, large abdominal white patches in addition to one on the shoulders. This individual is also the only one having general dilution of color in the pigmented body hair, and is further distinguished by having the unpigmented areas snow-white, as contrasted with a dirty brownish-white in the others. Only one of the six conspicuously marked specimens were collected at random. One from Woodward County was discovered in a group of 34 brought down by a pistol-shot. The one from Major County was secured