The Effect of Auditory Enrichment on Abnormal, Affiliative, and Aggressive Behaviors in Laboratory-Housed Rhesus Macaques (Macaca Mulatta)
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Research has shown that environmental enrichment can reduce abnormal behaviors in captive primates. However, auditory enrichment has generated mixed results. The purpose of this study was to determine if two types of auditory enrichment, white noise and designer music, were effective at reducing aggression and abnormal behavior, while also increasing affiliative behaviors in laboratory-housed rhesus macaques (Macaca mulatta). Forty laboratory-housed rhesus macaques at the Oregon National Primate Research Center were observed for 19 days over a 4 week period. During the first week, subjects were observed with no music to acquire a baseline level of behaviors (Phase 1). During week 2 subjects were exposed to white noise for three hours a day for five days (WN Phase). During week 3, designer music was played for three hours a day for five days (DS Phase). Observations continued into week four to determine if changes in behavior were residual (Phase 4). Results show that white noise was able to significantly increase affiliative behaviors, such as rates of social play and grooming. However, the white noise had minimal effect at reducing aggression or reducing the expression of abnormal behaviors. Designer music was found to decrease aggression but this was not correlated with the TEST period when the music was played. The designer music was found to significantly reduce abnormal behaviors and also significantly increase rates of social play and time spent in active exploration. Importantly, these behavioral changes were significant during the TEST period when the designer music was being played to the animals. The designer music was also effective at significantly reducing abnormal behaviors in those animals with adverse early rearing conditions (e.g., nursery-rearing). This study finds that auditory enrichment, specifically designer music, is an effective enrichment strategy to reduce abnormal behaviors and increase affiliative behaviors in laboratory-housed rhesus macaques.