Aggression Dynamics and Hormone Fluctuations in Black and White Ruffed Lemurs (Varecia variegata)

Black and white ruffed lemurs (Varecia variegata) are critically endangered primates from the Northeastern rainforests of Madagascar. This species shows clear female dominance in both feeding and social contexts. In captivity, this dominance hierarchy can lead to heightened aggression between females during the breeding season, which can result in animal separation or group reconfiguration. The objectives of this study are to determine the scope of this species-specific management strategy throughout AZA-accredited zoos, determine the influence of two types of feeding enrichment on aggression levels, and determine the effect of aggression on stress levels by measuring fecal glucocorticoids (fGC). Understanding aggression and its potential effects on stress levels can help animal managers keep multi-female groups together long-term, which promotes natural grouping configuration and social interactions. The multi-institution survey had a 90.9% response rate, with 70% of zoos reporting heightened aggression in their groups. A total of 52 hours of behavioral data were recorded by live observation and video at the Saint Louis Zoo and fecal samples were collected from all females daily. Study groups included a multi-female family group (3 females and 3 males) and an unrelated group consisting of 1 female and 2 males. Aggression rates were higher when food was presented in more complex enrichment feeders (males and females: n=802 interactions, p<0.10, exact sign test; females only: n=604 interactions, p<0.05, Wilcoxon signed-rank test), which is contrary to a previous study for this species. Furthermore, the breeding female living in the multi-female group shows significantly higher fGC than the female housed with only males (*n=179, p<0.001, exact sign test). Potential management strategies and future research can be suggested from these results.