Effects of outdoor housing on self-injurious and stereotypic behavior in adult male rhesus macaques (Macaca mulatta).

We examined the effects of outdoor housing on self-injurious and stereotypic behavior in adult male rhesus macaques with a history of self-wounding that were previously singly housed indoors for at least 4 y prior to the study. Baseline behavioral observations were collected over 2.5 mo. In phase 1, animals were relocated outdoors in 1 of 2 experimental conditions, group-housed (n = 8) or single-housed (n = 5), for 6 wk. In phase 2, group-housed animals were observed outdoors for an additional 6 wk. Behavioral observations were done using focal sampling techniques. In phase 1, rates of self-biting and self-directed stereotypies and time spent displaying idiosyncratic self-directed stereotypies decreased significantly when group- and single-housed animals were housed outdoors. Rates of yawning and scratching were significantly decreased for group- and single-housed animals and, for group-housed animals, self-grooming decreased with outdoor housing. In phase 2, rates of self-biting, time engaging in idiosyncratic self-directed stereotypies, and yawning remained significantly lower during weeks 7 through 12 (outdoor housing) compared with those under indoor housing. Rates of scratching and time spent self-grooming decreased significantly during the first 6 wk but then returned to baseline levels. Our findings suggest that self-biting and self-directed stereotypic behavior in rhesus macaques with a history of self-injurious behavior is significantly reduced by outdoor housing regardless of whether animals are socially or individually housed.