RANK RELATIONS AMONG SISTERS IN SEMI-FREE-RANGING BARBARY MACAQUES (MACACA-SYLVANUS)

Although semi-free-ranging Barbary macaque females are able to outrank older females from lower-ranking matrilines (matrilineal rank acquisi tion), they do not systematically outrank their older sisters, as is k nown to be the case for semi-free-ranging rhesus monkeys (Macaca mulat ta) and Japanese macaques (Macaca fuscata). We test the hypothesis tha t differences in the support received by younger sisters against their older sisters and against older lower-ranking females might account f or this interspecific difference. Thirty-one sister dyads, members of a group of 109 Barbary macaques living at La Montagne des Singes, Fran ce, were observed during 16 months. The results indicate that (1) all females were dominant to their younger sisters, and the latter were ne ver observed to challenge their older sisters; (2) younger sisters rec eived as much kin support against their older sisters as against older lower-ranking females; (3) only very young females received support f rom their kin against their older sisters; (4) younger sisters receive d much more support from nonkin females against lower-ranking females than against their older sisters; and (5) Barbary macaque females appe ar to be supported against their older sisters less frequently than rh esus macaque females are. We conclude that the lack of nonkin support is the main factor accounting for the failure of younger sisters to ou trank their older sisters in Barbary macaques. Initially this might re sult from kin support not being sufficient to induce younger sisters t o challenge and to solicit support against their older sisters.