Observations of increased activity and tool use in captive rhesus monkeys exposed to troughs of water

This study investigated the effects of water troughs on nonhuman primates housed in a captive environment. Two groups of rhesus monkeys ( Macaca mulatta ) were exposed to water‐filled troughs under three conditions: (1) standing water, (2) running water, and (3) a replication of standing and running water with novel objects. The effects of water exposure were assessed using a pretest phase (baseline), test phase (trough present), and posttest phase (baseline) design for each of the three conditions. Standing water produced different effects from running water. Monkeys were more active in the presence of standing water (higher levels of exploration and lower levels of social contact and grooming) than during baseline observations. In contrast, they were significantly more passive during the running water condition (higher levels of social contact) than baseline. Neither physical condition nor responses to dominance testing varied systematically over phases or between conditions. Tool use was observed during the standing water phases of Conditions 1 and 3. Three females from one group used a variety of cup‐like containers as drinking utensils. A larger number of animals used the trough to soak chow prior to ingestion, and virtually all of the animals used the trough as a drinking source. These results suggest that exposure to water sources may elicit a broad spectrum of species‐typical activity and may be a simple and inexpensive way to enrich the environment of captive rhesus monkeys. © 1993 Wiley‐Liss, Inc.