SPATIAL BENEFITS AFFORDED BY HIGH RANK IN WHITE-FACED CAPUCHINS

Group living is a source of both costs and benefits for animals. Benef its may include decreased predation risk, and an increased ability to find food and defend clumped resources; the most prominent cost is pro bably increased competition for food within the group. Presumably, ani mals will always try to minimize the cost they receive relative to the corresponding benefit. Since costs and benefits will vary between spa tial positions within the group, animals should prefer those spatial p ositions with the lowest costs relative to benefits. For groups whose members are organized by a social dominance hierarchy, access to prefe rred spatial positions may be a benefit of high rank. We examined the relationship between dominance rank and spatial patterns in two groups of white-faced capuchins, Cebus capucinus. We expected the animals to be faced with two cost-benefit gradients: predation risk increasing f rom centre to edge, and depletion costs increasing from front to back. Depletion was a significant factor in the dry season but not in the w et season; therefore, presumably only the predation risk gradient was present in the wet season. Dominant animals were more central than the ir subordinate counterparts during both seasons, and within the centre , they preferred the most forward position during the dry season but n ot during the wet season. The absence of variation in agonism across s patial positions suggests that active exclusion of subordinates by dom inant animals cannot explain the spatial patterns observed. Instead, w e conclude that subordinates avoid dominant animals as a strategy to r educe contest competition. (C) 1997 The Association for the Study of A nimal Behaviour.