In areas with sufficient food, such as agricultural land, breeding can occur year-round, with up to four litters being born each year. In the north, and other, less hospitable, environments, it occurs only during the spring. The local habitat also affects the age at which females begin breeding, with nearly half doing so in their first year in agricultural land, but none at all in desert scrub. Females can breed within the same season they are born, or within three months of their birth. Males tend not to breed until the season after they are born, or at least until they are 6–8 months old.