Trauma rates and patterns in specific pathogen free (SPF) rhesus macaque (Macaca mulatta) groups

Abstract

There are some predictable patterns of trauma in captive rhesus macaque (Macaca mulatta) social groups. Several factors have been documented to contribute to these patterns, including group formation of unrelated animals, and the establishment of dominance ranks. Here, we report on how socially induced trauma in groups of rhesus monkeys is influenced by the breeding season, numbers of matrilines per group and matriline size. We analyzed 3 years of data collected from veterinary admittance logs for four groups in our specific pathogen free (SPF) breeding colony. Since the groups differed in time from formation, both the numbers of matrilines and the composition of those matrilines were different. Across the four groups, trauma rates were significantly higher during the fall breeding season than the spring and summer months when births occur. The group that was formed most recently, comprised of the greatest number of matrilines but fewest related animals, showed significantly higher rates of trauma than the older social groups. Further, the middle and lowest ranking families received signifincantly higher rates of trauma than the highest ranking families, suggesting a rank-related phenomenon. Additionally, there was a significant negative correlation between numbers of adult females in a matriline and rates of trauma observed in each matriline, but the numbers of adult females are significantly higher in the top ranked families compared to all of the other matrilines. These findings suggest that trauma rates increase during the breeding season and may be exacerbated in recently formed breeding groups that have smaller matrilines and reduced opportunities for social support to mitigate rank-related aggression. Management practices should be devised to ensure adequate matrilineal size to decrease rates of trauma in captive rhesus macaque groups.

Sex and season predict wounds in zoo‐housed Japanese macaques (Macaca fuscata): A multi‐institutional study

“…The authors also report that wounding did not increase during the breeding season as had been previously reported under free‐ranging conditions (e.g., Drickamer, 1975), but instead increased during the birth season. In addition to seasonality and sex, other predictors of wounding in captive groups of rhesus macaques have included sex ratios and conflict intervention behavior (Beisner et al, 2012), and cohesive matrilineal structures (Beisner, Jackson, Cameron, & McCowan, 2011; Stavisky, Ramsey, Meeker, Stovall, & Crane, 2018). These studies contribute to our understanding of the factors that influence wounding in related macaque species, but as of yet, there are no published studies on factors influencing wounding frequencies in our species of interest, Japanese macaques.…”

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

“…Further, because the sex ratio changed (from 2.6 to 6.6 females per male) between the two studies, the effects of season and sex ratio are confounded in these analyses. We suspect; however, that the change in sex ratio may have had a larger effect on trauma than season because our group‐level analyses showed that total trauma was more frequent during the spring birth season than the fall mating season, which is in contrast to the expected increase in aggression and/or trauma due to mating season competition (Stavisky et al, ; Wilson & Boelkins, ).…”

“…Furthermore, although foraging enrichment may alter aggression frequencies, the impact on socially inflicted traumas is unclear because the rates of aggression do not necessarily predict rates of trauma (Beisner, Wooddell, Hannibal, Nathman, & McCowan, ; Pomerantz & Baker, ; Ruehlmann, Bernstein, Gordon, & Balcaen, ). Rather, trauma can be mediated by other internal (e.g., policing, sex ratio: Beisner, Jackson, Cameron, & McCowan, ; matrilineal fragmentation: Beisner, Jackson, Cameron, & McCowan, ) and external (e.g., season: Stavisky, Ramsey, Meeker, Stovall, & Crane, ) factors. Therefore, the effect of foraging enrichment on trauma outcomes needs to be directly tested.…”

Effects of medroxyprogesterone acetate on social behavior in female rhesus macaques (Macaca mulatta) depend on male breeding season introductions

“…Furthermore, social group instability can sometimes lead to matrilineal overthrows (in which related females fight and reverse rank with another group of related females) that can result in severe physical trauma and, in some cases, the death of members of the deposed matrilines 18,19 . Rhesus aggression and wounding are more frequent and more intense in the breeding season with increases in competition for access to breeding partners 20,21 . Coincident with breeding season is the introduction of new males to female social groups in some years, because females are more receptive to the presence of the unfamiliar males at that time 22,23 .…”

“…18,19 Rhesus aggression and wounding are more frequent and more intense in the breeding season with increases in competition for access to breeding partners. 20,21 Coincident with breeding season is the introduction of new males to female social groups in some years, because females are more receptive to the presence of the unfamiliar males at that time. 22,23 Therefore, understanding the impacts of MPA treatment on female rhesus social behavior, particularly during introductions of males during the breeding season, is important for maintaining the stability of matrilines in large captive breeding groups, and for mitigating rates of aggression and wounding, which are common concerns among those managing breeding colonies of rhesus macaques.…”