Sexing or Gender Determination in Small Mammals

Key Points

  • Examine anogenital distance to determine gender in neonatal rodents and in chinchillas of all ages. The distance between the anus and the urogenital region is relatively short in female rodents and longer in males.
  • Sexing can be challenging in chinchillas since the clitoris and penis morphology appear quite similar, however the anogenital distance is approximately twice as long in males.
  • Use external anatomy to sex adult hedgehogs, sugar gliders, ferrets, rabbits as well as rodents such as the guinea pig, rat, and hamster.
  • The testicles may be retracted into the abdomen of the adult rabbit as well as many species of rodents.
  • Mature males are often larger than females, except in chinchillas where the females are generally larger.

External reproductive anatomy is obvious in some adult small mammals such as the ferret, sugar glider, hedgehog, rat, guinea pig, and hamster. Gender determination or sexing can be challenging in some species like the chinchilla, and in many neonatal rodents. In these cases, reliance on anogenital distance or the distance between the rectum and the urogenital region is considered best practice . . .

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Banks RE, Sharp JM, Doss SD, Vanderford DA. Exotic Small Mammal Care and Husbandry. Durham, NC: Wiley-Blackwell; 2010.

Bedford J, Mock O, Nagadas S, et al. Reproductive characteristics of the African pygmy hedgehog (Atelerix albiventris). J Reprod Fertil 120(1):143-150, 2000.

Mitchell MA, Tully TN. Manual of Exotic Pet Practice. St. Louis, MO: Saunders Elsevier; 2009.

Quesenberry KE, Carpenter JW (eds). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery, 2nd ed. Philadelphia: WB Saunders Company; 2003.

To cite this page:

O'Rourke D. Sexing or gender determination in small mammals. June 3, 2010. LafeberVet Web site. Available at