title: Chimpanzees create and modify probe tools functionally: A study with zoo-housed chimpanzees.
abstract: Chimpanzees (Pan troglodytes) use tools to probe for out-of-reach food, both in the wild and in captivity. Beyond gathering appropriately-sized materials to create tools, chimpanzees also perform secondary modifications in order to create an optimized tool. In this study, we recorded the behavior of a group of zoo-housed chimpanzees when presented with opportunities to use tools to probe for liquid foods in an artificial termite mound within their enclosure. Previous research with this group of chimpanzees has shown that they are proficient at gathering materials from within their environment in order to create tools to probe for the liquid food within the artificial mound. Extending beyond this basic question, we first asked whether they only made and modified probe tools when it was appropriate to do so (i.e. when the mound was baited with food). Second, by collecting continuous data on their behavior, we also asked whether the chimpanzees first (intentionally) modified their tools prior to probing for food or whether such modifications occurred after tool use, possibly as a by-product of chewing and eating the food from the tools. Following our predictions, we found that tool modification predicted tool use; the chimpanzees began using their tools within a short delay of creating and modifying them, and the chimpanzees performed more tool modifying behaviors when food was available than when they could not gain food through the use of probe tools. We also discuss our results in terms of the chimpanzees' acquisition of the skills, and their flexibility of tool use and learning.
authors.affiliation: Lester E Fisher Center for the Study and Conservation of Apes, Lincoln Park Zoo, Chicago, Illinois; School of Psychology, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Lydia M
authors.initials: LM
authors.lastname: Hopper
authors.forename: Claudio
authors.initials: C
authors.lastname: Tennie
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Ross
authors.forename: Elizabeth V
authors.initials: EV
authors.lastname: Lonsdorf
mesh_terms: D000818:Animals; D000836:Animals, Zoo; D001522:Behavior, Animal; D004777:Environment; D005247:Feeding Behavior; D005260:Female; D005502:Food; D020049:Isoptera; D008297:Male; D002679:Pan troglodytes; D053001:Tool Use Behavior
keywords: chimpanzee; learning; probe tool; tool modification; tool use