Effects of altered enclosure size and substrates on squirrel monkey (Saimiri sciureus sciureus) behavior.

Abstract

We evaluated the effects of decreasing spatial density and changing substrate availability on activity, social spacing, and substrate use in a well-established, social group of 12 squirrel monkeys (Saimiri sciureus sciureus). Using instantaneous scan samples, we recorded the specific activity, distance to nearest neighbor, and substrate type for each animal at 10-min intervals during daylight hours and at three variations in spatial density and substrate availability. Decreased spatial density was accompanied by significant increases in locomotion and mean interindividual distance. Contact behavior remained constant regardless of spatial density. There were no significant differences in time spent in activities with change in substrate availability, but mean interindividual distance decreased from 0.82 m to 0.69 m when more suspended log substrates were available but spatial density was constant. These results indicate that changes in preferred substrate availability may significantly affect social spacing in a captive primate social group. The importance of species substrate preferences should be considered to enhance group cohesiveness when captive enclosures are designed for nonhuman primates.