Optimal group size, dispersal decisions and postdispersal relationships in female African lions

We used 40 years of long-term data to test whether dispersal decisions of female African lions, Panthera leo, are sensitive to variations in pride size, interpride competition and the quality of their natal territory. Per capita reproductive success reached a maximum at 3–6 females on the open grass plains of the Serengeti and at 3–11 females in the woodlands. Approximately 50% of female cohorts dispersed when potential pride size exceeded the habitat-specific optimum, whereas only 9% of cohorts dispersed at smaller pride sizes. Cohorts of one to two females rarely dispersed, especially in high-density habitats. Thus, pride size typically remained within the range that maximized individual reproductive success. In the high-density woodland habitat, females were less likely to disperse from prides that were surrounded by large numbers of unrelated females, as would be predicted on the basis of habitat saturation. However, the number of unrelated neighbours did not affect dispersal decisions of females living in the sparsely occupied plains habitat. After pride fission, daughters settled closer to their mothers in areas where there were greater numbers of unrelated female neighbours, but territories were just as exclusive as between unrelated neighbouring prides. Maternal prides in high-quality areas shared a greater percentage of their territory with descendant prides, but this tolerance diminished as relatedness declined through time.