Variation in space use and social cohesion within and between four groups of woolly monkeys (lagothrix lagotricha poeppigii) in relation to fruit availability and mating opportunities at the tiputini biodiversity station, Ecuador

Abstract

Like other members of their subfamily (e.g., spider monkeys and muriquis), woolly monkeys have long been suspected to have flexible association patterns. Yet, the dispersed nature of woolly monkey groups as they perform their daily activities has made it difficult for previous studies to quantitatively describe how spatial cohesion and ranging dynamics, both within and between groups, may vary over time and in relation to temporal fluctuations in resources, such as fruit and mating opportunities. Using a combination of location and subgroup composition records collected by multiple observers on animals belonging to four neighboring social groups, we found that lowland woolly monkeys (Lagothrix lagotricha poeppigii) at the Tiputini Biodiversity Station in Amazonian Ecudaor demonstrate relatively high degrees of fission-fusion dynamics, with groups dividing frequently into subgroups and showing temporally variable cohesion among group members. Associations were not limited to members of a single social group, and tolerant associations between members of some neighboring social groups occurred with relatively high frequency. As observed in other woolly monkey populations, home range overlap between neighboring groups was extensive, with particular pairs of groups showing higher degrees of overlap than others. Although woolly monkeys are considered non-territorial, the four focal social groups retained some exclusivity of their core areas as evidenced by minimal core area overlap during most months of sampling for most pairs of groups. Surprisingly, habitat-wide estimates of fruit availability had little to no influence on the observed variation in group cohesion and ranging patterns among the four groups, while indices of mating opportunities did, suggesting that grouping and ranging dynamics in woolly monkeys may not primarily be the result of competition over food, but rather of competition over mates.