Memory and foraging theory: chimpanzee utilization of optimality heuristics in the rank-order recovery of hidden foods

• Published in: Animal behaviour Vol. 84; no. 4; pp. 795 - 803
• Main Authors: Sayers, Ken, Menzel, Charles R.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2012; Harcourt Brace Jovanovich Ltd
• Subjects: almonds; Animal cognition; Animal memory; bags; cognition; Cognitive ability; communication; Ecology; energy; evolutionary ecology; foods; foraging; Foraging behavior; handling time; Heuristic; humans; memory; Monkeys & apes; movement ecology; Pan troglodytes; prey encounter; primate cognition; profitability; vocalization; primate cognition; handling time; communication; evolutionary ecology; movement ecology; prey encounter
• ISSN: 0003-3472; 1095-8282
• DOI: 10.1016/j.anbehav.2012.06.034

Many models from foraging theory and movement ecology assume that resources are encountered randomly. If food locations, types and values are retained in memory, however, search time could be significantly reduced, with concurrent effects on biological fitness. Despite this, little is known about what specific characteristics of foods, particularly those relevant to profitability, nonhuman animals can remember. Building upon previous observations, we hypothesized that chimpanzees, Pan troglodytes, after observing foods being hidden in a large wooded test area they could not enter, and after long delays, would direct (through gesture and vocalization) experimentally naïve humans to the reward locations in an order that could be predicted beforehand by the spatial and physical characteristics of those items. In the main experiment, various quantities of almonds, both in and out of shells and sealed in transparent bags, were hidden in the test area. The chimpanzees later directed searchers to those items in a nonrandom order related to quantity, shell presence/absence, and the distance they were hidden from the subject. The recovery sequences were closely related to the actual e/h (energy/handling time) profitability of the foods. Predicted recovery orders, based on the energetic value of almonds and independently measured, individual-specific expected pursuit and processing times, were closely related to observed recovery orders. We argue that the information nonhuman animals possess regarding their environment can be extensive, and that further comparative study is vital for incorporating realistic cognitive variables into models of foraging and movement. ► Chimpanzees recovered hidden foods in order of their e/h (energy/handling time) profitability. ► Chimpanzees remembered multiple details of foods. ► Researchers, using foraging theory variables, could predict food recovery order.