First record of melanism in the white-tailed antelope squirrel Ammospermophilus leucurus (Mammalia: Sciuridae)

Abstract

The white-tailed antelope squirrel Ammospermophilus leucurus is a rodent species distributed from northwestern Mexico to southwestern United States. It is characterized by its small size and a light brown coloration with two white stripes on its back. It usually inhabits arid zones, from plains with xerophilous vegetation to mountainous cliffs. A field visit was carried out during midday on May 11th, 2023, in the volcanic area of Las Tres Virgenes within the El Vizcaino Biosphere Reserve, Baja California, Mexico. Specifically, the transect walked was within Del Azufre canyon, characterized by rocky walls and cliffs, as well as small caves. During the field walk, a melanistic individual of A. leucurus was observed between rocky substrates on the walls and debris of the canyon. The individual measured approximately 20 cm and exhibited vigilance in both horizontal and vertical positions. This observation represents the first documented case of melanism within the antelope squirrel genus Ammospermophilus. Further research, such as genetic or ecological analyses, can determine the frequency of melanism in this species as well as its influence on behaviour and survival.