The Arizona gray squirrel (Sciurus arizonensis) is a species of squirrel found mainly in Arizona, but also in western New Mexico and in the very north of the State of Sonora, Mexico. It is a fairly large squirrel, growing to lengths of 40-50 cm (16-20 in). It has gray fur and a creamy white belly. It can be distinguished from the similar Abert’s squirrel (Sciurus aberti) by having smaller ears with no tufts and a red or black stripe on the underside of the tail. There is a difference in size between males and females, but which sex is the bigger depends on the population, with some populations having larger males and other populations having larger females.
The Arizona gray squirrel lives in decidious and mixed forests in valleys, canyons and on mountains at mid-level altitudes. It is typically found at elevations between 1,500-1,800 m (5,000-6,000 ft). Walnuts are its most important food source, but it will also eat other nuts, pinecones, berries, seeds and fungi.
Breeding season for the Arizona gray squirrel is in April-May, which correlates with spring flowering. This period provides the nutrients to sustain the exhausting endavaour of chasing competition, mating and rearing young, but because food availability can fluctuate every year, not all females mate and rear young each season. This ensures the overall survival of the species, even when there is a shortage of food.
Several males will chase a female ready to mate, and the home ranges between individuals tend to overlap a lot more during the breeding season. Once impreganated, the female will build a nest made out of leaves which will be placed up in a tree, preferrably with dense canopy cover. The young are born after a gestation period of around two months, and the litter size is normally between two and four.
The Arizona gray squirrel is a shy species and seldom seen. It is not well studied, and the numbers are not known. The population size seems to flucutate every year. It is listed as data deficient on the IUCN Red List. Major threats are destruction of habitat and wildfires. Another threat is the introduction and range expansion of the Abert’s squirrel, which can outcompete the Arizona gray squirrel.