Effects of positive reinforcement training on infant behavioral development in nursery-reared rhesus macaques (Macaca mulatta) (2009)

Brunelli, R. L., Gottlieb, D., Holcomb, K. et al.

Abstract

At the California National Primate Research Center, one key to long-term success of macaque breeding colonies is to develop effective infant-rearing strategies that minimize the emergence of behavioral pathologies, which can be one indicator of welfare. Positive reinforcement training (PRT) is often used for husbandry and exhibition, but few quantitative studies have evaluated its potential as environmental enrichment for increased welfare. Our study objective was to investigate PRT in nursery-reared infant rhesus macaques to assess whether it could be used to normalize development. Ten infant monkeys were trained from age 3 through 112 days, for 40 minutes total per week each. Ten nontrained infants were observed as controls. One-zero focal observations were performed during nontraining periods and one month following the cessation of training, and follow-up focals from age 8–9.5 months. Biobehavioral assessment of temperament was also conducted. Data were analyzed using a random-intercept negative binomial regression model. Trained animals showed a higher level of tactile/oral behavior later in development than early [β = 1.25, p = 0.085], but not control animals. Both trained and control groups showed a significant increase in motor stereotypy across developmental stages. But, later in development, trained animals showed significantly less motor stereotypy than control animals [β =0.516, p=0.095], which was not found earlier in development. Our results show that PRT has the potential to normalize certain aspects of development in nonhuman primates.