| Spatial Structure during Travel in Pithecia pithecia Cunningham, E.P. The spatial position of members of a group during travel can affect individual fitness. Peripheral positions increase the chances of discovering feeding sites, but also increase the likelihood of predation. Spatial structure is expected to be clearly defined when individuals compete aggressively for resources. In this paper, I examine the spatial structure of a group of six white-faced sakis (Pithecia pithecia) during travel on Round Island in Guri Lake, Venezuela. Although white-faced sakis do not generally display high rates of aggressive interactions, they compete for limited resources. While traveling, sakis tend to search for small, scattered resource sites. The position and activity of each member of the group was recorded every 30 minutes during 47 all-day follows. Individual positions were analyzed in terms of centrality and the direction of group travel. The results indicate that adult males tended to occupy peripheral positions, often in the front, adult females were most variable in their positions, the juvenile male tended to be found in central positions, and the juvenile female, who was most often displaced from limited resources, spent more time in peripheral positions. Considered in relation to heightened predation risk for juveniles, the results suggest that both predation and resource competition influence individual position. Return to symposium programme |