Female eviction, abortion, and infanticide in banded mongooses (Mungos mungo):: implications for social control of reproduction and synchronized parturition

Most cooperatively breeding species exhibit high reproductive skew, where reproduction within the social group is monopolized by a dominant pair. In many of these species, social control of reproduction is the mechanism driving reproductive skew: individuals within the social group actively reduce the reproductive success of others. In species where females do not suppress conception in other females, alternative routes to skewing the social group's reproductive output include inducing abortion in rivals, evicting them, or killing their young. This study examines instances of female eviction, abortion, and infanticide in a cooperatively breeding species with low preparturition reproductive skew, the banded mongoose (Mungos mungo). Although instances of these behaviors are rare in this species, aspects of their occurrence have implications for social control of reproduction. Abortion can be induced by the stress of being evicted. The readmittance of females that abort suggests that reducing communal litter size is a possible selective pressure for eviction. This is supported by the occurrence of eviction events in groups with relatively high numbers of reproductive females and by the eviction of young reproductive females. The timing of abortion events suggests that synchronization of parturition with other females in the group is a major selective pressure. Infanticide could represent the selective pressure for synchronized parturition. Alternatively, synchronization may minimize competitive asymmetry between pups born to different females. This paper also describes incidences where a female aborts or gives birth to her litter over different days in order to synchronize parturition: behavior previously unrecorded in mammals.