Most female Panthera leo remain in their natal pride for their entire lives, but c 1/3 emigrate before they reach 4 yr of age. Most emigrating females leave either when they are evicted by an incoming male coalition or when the adult females of their pride give birth to new cubs. One cohort of females left because they avoided mating with males of their father's coalition. Cohorts of dispersing females leave together and form a new pride whose range almost always includes at least part of their natal range. Females that leave their natal pride suffer reduced fitness: dispersing females in the Serengeti first breed at a later age than non-dispersing females and dispersing Ngorongoro females suffer higher mortality. Dispersal patterns of large and small cohorts are such that pride size rarely exceeds or goes below the range of sizes that confers the maximum reproductive success per female. Pride fissions have no consistent effect on the average levels of genetic relatedness within prides. All males leave their natal pride. Most leave at a male takeover. Larger male coalitions are more likely than small ones to gain residence in a pride adjacent to their natal pride, and also gain their first pride at a younger age. However, not all large cohorts are so successful because most cohorts of 6-8 males permanently split up soon after emigrating from their natal pride. -from Authors
Bibliographical noteFunding Information:
') We thank the Government of Tanzania for permission to conduct research and the Serengeti Wildlife Research Institute for facilities. We also thank Jeannette HANBYa nd David BYCOTTfo r valuable information, Sara CAIRNS,M onique BORG ERHOFF-MULDER and Anthony COLLINSf or maintaining demographic records in our absence, and Jon ROODa nd Peter WASERf or their comments on an early draft of this paper. This work was supported by grants from the Graduate School of the University of Minnesota and NSF grants BSR-8406935 and 8507087.