How can the sex of a Richardsons ground squirrels be determined?
Although male Richardson’s ground squirrels are larger than females, the difference in size is hard to distinguish from a distance. The most reliable way to sex a ground squirrel is by looking at the ano-genital distance, but this requires having the animal in hand. The ano-genital distance is longer in males than in females, with the scrotal skin of the male accounting for the additional distance between the anus and the urinary opening. Because the testes descend into the scrotum for only about 4 weeks a year (see Reproduction), most of the time there is no conspicuous bulge in the scrotal area of males. During the mating season, when males engage in fights that result in severe wounds, males can often be distinguished from a distance by their tattered and torn appearance.
