Human-directed contra-aggression training using positive reinforcement with single and multiple trainers for indoor-housed rhesus macaques

Abstract

The objective of this study was to improve human–animal management relationships by testing the effects of positive reinforcement training (PRT) on reducing human-directed aggression in rhesus monkeys ( Macaca mulatta). Contra-aggression uses a combination of positive reinforcement training techniques designed to actively reduce instances of aggressive behavior. Additionally, this study looked at how much post-training generalization occurs between the staff who trains an animal and non-training staff interacting with trained animals. Three training treatments were applied: a non-training group (controls; N = 5), monkeys conditioned by a single trainer (ST; N = 5), and monkeys conditioned by multiple trainers (MT; N = 5). Each macaque received two tests (human-intruder, husbandry-response) to evaluate behavioral changes prior to training, when training ceased, and after a 6-week non-training period. The tests assessed the level of training generalization to human interaction. There was no marked improvement in animal progression through the training plan from single to multiple trainers ( P = 0.927), which is inconsistent with current training philosophy; however, both single and multiple trainer groups showed a significant reduction of aggression (ST: P ≤ 0.001, MT: P < 0.001) during training. The two tests showed a marked reduction of aggression outside training sessions in the training groups (human intruder: P ≤ 0.001; husbandry response: P = 0.01); however significance was not achieved in the non-training group. These preliminary results indicate that contra-aggression training and PRT in general can reduce aggressiveness in nonhuman primates, and such reduction could enhance their well-being during routine research and medical procedures.