On the evolutionary stability of female infanticide

Abstract Territoriality among female rodents may have evolved as an adaptation to intraspecific compe-tition for resources or, alternatively, to defend pups against infanticide. In order to evaluate the latter, we analyse the conditions that allow an infanticidal strat-egy to invade a population of non-infanticidal females, and the circumstances under which infanticide may become an evolutionarily stable strategy (ESS). Our game theoretical analyses indicate that infanticide has to be associated with some direct (cannibalism) or in-direct (reduced competition) resource benefits in order to invade a non-infanticidal population. We also expect that females will primarily kill litters of nearby neigh-bors, thereby removing the closest competitors while keeping costs at a low level. However, once established in a population, infanticide may be an ESS, even if females do not gain any resource benefits. This is the-oretically possible if a female through infanticide can reduce the possibility that other, potentially infanti-cidal, females establish and/or stay close to her nest. While behavioral data indicate that these special cir-cumstances sometimes occur, they may be too specific to apply generally to small rodents. Therefore, we ex-pect that the evolutionary stability of infanticide often requires resource benefits, and that female infanticide in small rodents may, in fact, be a consequence rather than a cause of territoriality. Key words Evolutionary stability á Female behavior á Game theory á Infanticide á Small rodent