Inbreeding in Littledale's whistling rat Parotomys littledalei

Despite its rarity in nature, inbreeding is sometimes evident in species occupying ephemeral, unpredictable habitats, and which occur at low densities. One such species is Littledale's whistling rat, Parotomys littledalei, a murid rodent endemic to the south-west arid region of South Africa. Using a captive population of P. littledalei, I studied mate choice for kin and nonkin, and the reproductive performance of inbred and outbred pairs. In choice tests, estrous females presented with either odors or actual males showed a preference for siblings or half-siblings to unrelated males. Males did not discriminate between the odor of estrous kin and nonkin. In breeding studies, inbred (mother-son; brother-sister) and outbred (proven female and an unrelated young male and nonsiblings) pairs had a similar reproductive output, although the sex ratio favored males in inbred litters. The development of inbred young was indistinguishable from outbred young. The results indicate that female P. littledalei prefer to inbreed, but there are no apparent advantages to inbreeding over outbreeding.