Self-aggression in macaques: Five case studies

Spontaneous self-aggressive behaviors were observed in five adult male rhesus monkeys (Macaca mulatta) housed at a university facility. All were individually caged, were free of intercurrent disease, and were being utilized in ongoing research studies. The self-aggressive behaviors observed included self-biting, self-clasping, self-slapping, self-rubbing and threatening of body parts. In several cases, wounds were inflicted and medical treatment was required due to the severity of the lesions. A review of the animals' clinical histories revealed an increased level of self-aggressive behavior in four of five monkeys during such stressful or stimulating conditions as movement of the animal to a new cage, movement of animals out of the room or escape of other monkeys from their cages. The frequency with which these behaviors occurred was quantitated experimentally. The results revealed an increased level of self-aggressive behavior in two of these animals during the videotaped sessions in response to aggressive contacts with the investigator. In contrast, one monkey exhibited self-aggressive behavior both clinically and experimentally in the absence of environmental stimuli or human contact. Clinical management of self-aggressive monkeys included housing monkeys only with physically smaller primates, decreasing the level of environmental stimuli, and drug therapy. Haloperidol was used with success in one animal that exhibited severe self-aggressive behavior.