Ecological observations on the melanistic woodrats (Neotoma albigula) of Black Gap Wildlife Management Area brewster county of Trans-Pecos Texas

Blair (1954) first reported that the melanistic white-throated woodrats (Neotoma albigula) were mostly restricted to the dark basaltic formations on Black Gap Wildlife Management Area of Trans-Pecos Texas. This study reports on a series comprised of individuals of melanistic and of typical pelage in nearly equal proportions on the limestone flats, adjacent to lava flows which failed to procure any specimens. This contrasts to Blair's findings of melanistic woodrats largely restricted to the volcanic sediments of the region, where he found the species most common. The persistence of the melanistic condition only in the vicinity of some dark basaltic formations of the southwestern United States and adjacent parts of Mexico is compelling evidence for some level of selection. These findings suggest that spatial and temporal aspects of selection and stochastic features practically ensure fluctuating frequencies of occurrence of melanism in a population, and of interpopulational variation of the incidence of this color morph.