Richardson's ground squirrels are not sexually mature until they emerge from their first hibernation season, when they are about 11 months old. Richardson's ground squirrels are seasonal breeders, with mating restricted to a 2- to 3-week period in early spring. Soon after the brief mating season is over, the male's testes regress and return into an abdominal position, where they remain for the next 48 weeks. Each female mates on only one day during the mating season, after which she is pregnant and then lactating for the following 2 months. Females are incapable of having a second litter in the same year.
After males arouse from the final torpor bout of hibernation, their testes undergo recrudescence. Males frequently spend several days in the underground hibernaculum before they emerge above ground, so their testes are already enlarged and descended into a darkened scrotum by the time they appear at the surface.