A comparison of tool-use flexibility between captive chimpanzees and bonobos

Abstract

Despite chimpanzees and bonobos sharing close phylogenetic ties to humans, chimpanzees are the more common model species in multiple fields of comparative research. One reason for this bias is the variation in tool repertoire size observed between the two species. Previous studies have examined the factors driving this difference, but few have targeted flexibility in how tools are used. We studied bonobos and chimpanzees under similar conditions in captivity, thus excluding any ecological variation present in these species’ natural habitats. We examined whether the species differed in their ability to switch between tools, a trait that may facilitate tool innovation in primates. To do so, we provided the apes with a task that required switching tool type from a rigid stick to a bendable rope to forage successfully. Our data suggest that there are no significant differences in tool-use performance between chimpanzees and bonobos in captivity. However, we found significant differences in the species’ exploration tendencies. While chimpanzees fixed their attention on stick tools, bonobos switched their attention more easily towards the rope, potentially due to less functional fixedness. We also found significant within-species differences between institutions. These findings suggest that future research should disentangle intrinsic flexibility in exploration and account for institution and group level effects.