FEMALE MULTIPLE MATING-BEHAVIOR IN THE COMMON SHREW AS A STRATEGY TO REDUCE INBREEDING

Three hypotheses concerning potential genetic benefits of female multi ple mating behaviour are evaluated for the common shrew. In a high-den sity population, many successful copulations took place between indivi duals estimated to be close relatives (e.g. full or half siblings). Ju veniles resulting from such matings tended to be relatively small at w eaning, and were generally less likely to survive to sexual maturity t han more outbred individuals. Multiple paternity was discovered in eig ht of nine litters examined. The incidence of matings between close re latives, the cost of inbreeding, and the high incidence of multiple pa ternity presented are each consistent with the hypothesis that female multiple mating is a strategy to reduce inbreeding. That is, if female s cannot always distinguish close kin, then they may copulate with sev eral different males and so reduce the risk that all their offspring w ill be sired by a close relative.