An Intergroup Encounter With Fatal Consequences in Yellow Baboons (Papio cynocephalus)

INTRODUCTION Interactions between permanent social groups of primates can range from group fusion to mutual avoidance to actual attacks on and even killing of members of one group by those of another. Competitive interactions between groups could be expected in a population in which groups use the same limited resources where their home ranges overlap. Theories of kin selection predict that such competition would be even more likely where intergroup migration is sufficiently low that individuals are more closely related, on the average, to members of their own group than to members of another. However, there is little direct evidence that intergroup competition exists. In populalions with documented genealogical and home-range information, there is little evidence of kinship effects in intergroup encounters. Migration of adult and subadult males occurs among groups of yellow baboons (Papio cynocephalus) that inhabit the woodlands and savanna of Amboseli National Park, Kenya [Altmann & Altmann, 1970; Altmann et al, 19771. However, there is a high degree of group integrity due to the virtual absence of adult female and juvenile migration. The following report describes an unusual event: the fatal wounding of an infant and the severe injury of its mother during an encounter between two of these baboon groups. It also gives an account of the role played by the wounded infant in agonistic interactions between adult males. Members of both groups were individually recognizable, and the reproductive histories of all the adult females involved were known through the accumulation of census and reproductive data [Altmann et al, 1977; Stein, 19811.