Caregivers Engaging in Monkey Business: Evaluating the Use of Caregivers as Social Enrichment for Captive Rhesus and Cynomolgus Macaques
Abstract
Enrichment recommendations for captive non-human primates prioritize group-housing to provide them with social enrichment, which is often not possible in laboratory environments, due to infrastructural and experimental constraints. Our objective was to test if caregivers could serve as effective social enrichment for captive rhesus and cynomolgus macaques and to see if there was an effect of the type of social behaviours they employed. Eight female pair-housed macaques (rhesus n=5, cynomolgus n=3) were split evenly into two treatment groups: human behaviour (HB) and monkey-like behaviour (MB). For monkeys in the HB group, caregivers would use only human behaviours while interacting with them. For those in the MB group, caregivers would attempt to replicate macaque social behaviours. Treatment occurred daily at 1pm, when the monkeys would receive fresh produce, and lasted three weeks. The caregiver would attempt to engage with each subject for 6 minutes: 2 minutes during feeding and 2 minutes before and after. Interactions were unstructured, and caregivers would gauge their behaviours based on the monkey’s reactions. Our results showed that monkeys were more likely to engage in interactions before feeding. During interactions, MB monkeys interacted less with the caregivers, showing lower rates of affiliative, submissive, and abnormal behaviour than HB monkeys (P < 0.10). Monkeys from both groups spent most of their time oriented towards the caregivers and at the front of their cages, showed a 2.2 ± 0.69% (7.9 sec, p = 0.058) increase in self-grooming behaviour, and a 3.4 ± 1.1% (or 12.4 sec, p = 0.087) reduction in negative interactions before feeding with their cage-mates. During times when no humans were present, HB monkeys displayed higher rates of certain abnormal behaviours, monkeys from both groups showed a 3.5 ± 1.5 (p = 0.0584) decrease in the frequency of cage-directed abnormal behaviours and a 1.2 ± 0.53 (p = 0.067) decrease in the frequency of stereotypic abnormal behaviours. All monkeys further saw a 12.9 ± 6.1% (7.71 min, p = 0.010) increase in the proportion of time spent interacting positively with cage-mates, including a 10.6 ± 4.78% (p = 0.077) increase in time spent grooming. Conversely, they saw a decrease in time spent interacting negatively, and a 0.54 ± 0.25% (19.44 sec, p = 0.090) decrease in proportion of time interacting aggressively. This contributes to our understanding of enrichment for non-human primates and presents an alternative way of providing social enrichment to macaques in research environments.