Deep incursion and use of a mineral lick within a neighboring territory by a group of white-bellied spider monkeys (Ateles belzebuth) in eastern Ecuador

Abstract

One convergent aspect of the societies of chimpanzees and spider monkeys is the fact that members of a social group jointly conduct territorial boundary patrols and raids into home ranges of neighboring groups. Boundary patrols are usually perpetrated by subgroups of adult and subadult males who travel in silence into neighboring territories. Only rarely do females participate in these incursions. Moreover, for spider monkeys living in the western Amazon, mineral licks (or ‘salados’) seem to be key areas where animals descend to the ground and consume water and soils, most likely to acquire minerals not readily available in their diet. Based on 10 years of behavioral research, here we document a unique case in which most members of one group of white-bellied spider monkeys (Ateles belzebuth) collectively made a deep incursion into a neighboring group’s territory and used a mineral lick well within a that group ́s range. This particular event raises the intriguing questions of what knowledge group members might possess about locations of key resources in adjacent territories, how they acquire this knowledge, and what motivates the use of those resources, especially when groups have other mineral licks they can frequent within their own territories. Although occasional deep incursions into other group’s ranges may be part of the repertoire of intergroup interactions engaged in by wild spider monkeys, the underlying explanation behind the decision to visit and consume soil from mineral licks in neighboring territories remains largely unexplained.