Mating Strategies in Relation to Sexually Selected Infanticide in a Non-Social Carnivore: the Brown Bear

The concept of sexual selection, as first proposed by Darwin (1871), predicts that the fundamental reproductive asymmetries between males and females give rise to a conflict between sexes. Male reproductive success tends to be limited primarily by access to mates, whereas female reproductive success is usually limited by access to resources. Infanticide, the killing of dependent young by conspecifics, is a wellknown phenomenon among animals and can be regarded as a component of this intersexual conflict (Hrdy 1979; Hrdy & Hausfater 1984). Sexually selected infanticide (SSI) refers to competition for breeding opportunities and is more prevalent in polygynous mating systems. Three prerequisites are needed to consider infanticide as sexually selected: (1) infanticide shortens the time to the mother’s next estrus, which consequently increases the infanticidal male’s own opportunity to breed, (2) the perpetrator is not the father of the infants he kills, and (3) perpetrators have a higher probability of siring the female’s next litter (Hrdy & Hausfater 1984). The known cases of infanticide by male mammals are remarkably concentrated in a few orders and have mainly been described in social species, partiCorrespondence Jon E. Swenson, Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, Pb. 5003, NO-1432 Ås, Norway. E-mail: [email protected]