Behavioral predictors of pairing success in rhesus macaques (Macaca mulatta)

Abstract

Pair housing is one of the most important components of behavioral management for caged macaques; however, it can result in aggression and injury if partners are incompatible. Knowing when to proceed and when to stop social introductions can be challenging, and can have consequences for the partners. We examined whether behavior early in social introductions predicted success (i.e., partners remained co-housed with full contact for at least 28 days) in 724 female-female and 477 male-male rhesus macaque pairs. We took cage-side one zero focal observations on pairs during the first two days of full contact, recording social and aggressive behaviors. The majority of pairs (79.6% of female, 83.0% of male) were successful. The most common behaviors exhibited by pairs during these observations were maintaining proximity, tandem threats, and anxiety. Mounting was also relatively common in male pairs. Grooming and close social contact (e.g., touching) were not common in our study. Several behaviors observed on Day 1 significantly predicted pairing success. For females, these included proximity, tandem threat, rump present, mount, and groom. Day 1 predictors of success for male pairs included proximity, tandem threat, rump present, mount, and social contact. Fewer behaviors predicted success on Day 2. Maintaining proximity on Day 2 predicted success for both sexes, but tandem threat predicted success only for females. Behaviors that predicted incompatibility for females on Day 1 included displace, grimace, threat, bite, and other aggressive contacts. Day 1 predictors of separation for male pairs were displaced, grimace, and abnormal behavior. The only Day 2 behavior that correlated with incompatibility was grimace, which was predictive for males. Interestingly, aggression did not predict incompatibility for male pairs. Identifying behaviors exhibited by monkeys early in the pair introduction that are predictive of long-term compatibility can shape pairing decisions, reducing later stress and potential injury.

Temperament Predicts the Quality of Social Interactions in Captive Female Rhesus Macaques (Macaca mulatta)

“…By doing so, we were able to assess whether pairing female rhesus macaques provides opportunities for positive experiences (and consequently, increase positive welfare) in addition to a reduction in negative ones. Studies that used introduction outcome as the response variable concentrated on whether pair-mates could remain together for a certain period following the termination of the introduction process (e.g., [ 36 , 37 ]). The determination of whether partners can remain co-housed is made according to the judgment of the behavioral management technician who introduces the animals.…”

“…Accordingly, so long as no overt and persistent aggression is observed, social partners tend to be left together even in the absence of affiliative interactions between them [ 45 ]. Moreover, the criterion for success, as it has been used, is somewhat arbitrary and ranges from the ability of partners to stay together in a shared space for a few days [ 36 ] to 4 weeks [ 37 ], and even months [ 46 ]. Therefore, methodical collection of behavioral data at different stages of the introduction process (as well as later, when the pairs have been together for some time) will enable behavioral managers to assess the quality of social interactions on a measurable scale independent of human interpretation.…”

“…The current study sought to build on previous research conducted by us and others [ 30 , 36 , 37 , 38 ] that identified predictors of pair success (i.e., can social partners remain together continuously in a shared space without persistent aggression and wounding). In particular, our recent study [ 36 ] demonstrated that, for female pair formations, three measures, taken from the California National Primate Research Center’s (CNPRC) BioBehavioral Assessment (BBA) Program (see Section 2.4 ) predicted success in pairings.…”

Self‐Injurious behavior in rhesus macaques: Issues and challenges

“…At the same time, there was a concerted effort at all primate facilities to pair‐house research monkeys and reduce the number of animals housed in individual cages. Although not all pairs are compatible, high rates of success were documented at one facility, yielding approximately an 80% success rate for monkeys placed in same‐sex pairings (MacAllister et al, 2020). A similar rate of success at another facility occurred when females were paired with vasectomized males (Ekanayake‐Alper et al, 2018).…”

Video Conference Technology as a Tool for Pair Introduction in Rhesus Macaques

“…In this study, we examined the use of the Zoom video conference app (on tablets) as a potential tool to assess pair compatibility in male and female rhesus macaques prior to relocation for pair introduction. Given that prosocial behavior exhibited early in the introduction can predict pair success [ 21 ], we hypothesized that pairs in which the partners demonstrated affiliative behaviors during the Zoom session would be more likely to be successfully pair-housed than those in which there was no prosocial behavior exhibited.…”