Increased produce enrichment reduces trauma in socially‐housed captive rhesus macaques (Macaca mulatta)

• Published in: American journal of primatology Vol. 81; no. 12; pp. e23073 - n/a
• Main Authors: Wooddell, Lauren J., Beisner, Brianne, Hannibal, Darcy L., Nathman, Amy C., McCowan, Brenda
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01-12-2019
• Subjects: Adaptation; Aggression; Aggressive behavior; Aggressiveness; Animals; Biomedical materials; Biomedical models; Climbing; Corn; Enrichment; environmental enrichment; Food; Food resources; foraging; Foraging behavior; Housing; Incidence; Injuries; Injury prevention; Levels; Mating; Proximity; Psychic assault; Psychological trauma; Public housing; Risk; Risk reduction; Squash; Toys; Trauma; Welfare; wounding; environmental enrichment; foraging; aggression; welfare; wounding
• ISSN: 0275-2565; 1098-2345
• DOI: 10.1002/ajp.23073

Due to primate adaptations for sociality, captive rhesus macaques have optimal welfare and utility as a biomedical model when they can be maintained in outdoor social groups. As a despotic species; however, aggression can result in costly injuries and may result in temporary or permanent removal of specific individuals from social housing. Enrichment items, such as toys, climbing structures, and foraging material, are employed to keep captive animals occupied. We hypothesized that produce enrichment that requires more processing to extract may reduce socially‐derived injuries by keeping animals occupied. We tested the effects of additional weekly produce (corn‐in‐husk, whole melon, or whole squash) on trauma incidence in an outdoor social group of rhesus macaques across two distinct seasons (mating and birthing seasons) at the California National Primate Research Center. Aggression and status behavioral data, food resource use and proximity, and trauma incidence were collected over two 16‐week periods, with eight control and treatment conditions alternating biweekly. Mixed‐effects regression modeling was used to determine the best predictors of trauma risk and severe aggression at the group level and at an individual level. We found that food resource use was an important predictor of trauma risk at both group and individual levels; greater use of food resources reduced trauma risk. Produce enrichment did not; however, reduce severe aggression. We suggest that other captive social groups of rhesus macaques with high levels of trauma may benefit from supplemental produce enrichment that increases animal engagement with food resources.
Count of total trauma per week across all 16 weeks of study for both Spring 2017 and Fall 2018 studies shows that overall, produce enrichment weeks had lower trauma compared to control weeks.
Research Highlights
Housing rhesus macaques in large‐outdoor social groups is ideal for their psychological welfare
Social aggression; however, can cause trauma
Extra produce enrichment that takes time to process decreases trauma in group‐housed rhesus macaques