Infanticide and control of reproduction in cooperative and communal breeders

Many communal breeders are characterized by a conflict over who gets to reproduce, with dominant individuals often claiming the largest share of reproduction in the group. How do dominants control breeding in these species? Although infanticide has often been invoked as a means of control, previous theoretical work on indiscriminate killing of young did not support this idea. There is, however, increasing evidence from field studies in both vertebrates and insects that infanticidal individuals can discriminate between their own offspring and those of other group members, and thus avoid the risk of accidentally killing their own progeny. In a simple game-theoretical model we demonstrate that the capacity for discriminate infanticide can promote high reproductive skew even though few or no offspring are actually killed. When discrimination is good and offspring are cheap to produce, the threat of infanticide prevents the subordinate cobreeder from adding many young to the joint brood, and no killing need occur. High levels of infanticide tend to occur only when discrimination is poor, costs of offspring production are low and/or relatedness is low. (C) 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.