Aggression in pigtailed macaque (Macaca nemestrina) breeding groups affects pregnancy outcome

Area of Science:

• Primate Behavior
• Reproductive Biology
• Animal Welfare

Background:

• Aggressive behaviors are known to influence reproductive outcomes in captive nonhuman primates.
• Understanding these dynamics is crucial for improving breeding program success and animal well-being.

Purpose of the Study:

• To investigate the relationship between specific aggressive behaviors and pregnancy outcomes in a colony of pigtailed macaques (Macaca nemestrina).
• To determine if aggression levels can predict the likelihood of natural birth, intervention-assisted birth, or nonviable outcomes.

Main Methods:

• Behavioral data on 11 distinct aggressive actions were collected over 22 weeks from nine breeding groups.
• Aggression levels were quantified weekly and analyzed using Principal Components Analyses.
• Pregnancy outcomes, including natural births, clinical interventions, and nonviable outcomes, were recorded.

Main Results:

• Pigtailed macaque aggression was categorized into five types: warn, engage, threaten, pursue, and attack.
• Significant differences in aggression levels were observed between breeding groups, independent of group size or stability.
• Higher levels of specific aggression categories were significantly associated with altered probabilities of various pregnancy outcomes, especially when clinical interventions were considered.

Conclusions:

• Aggression levels in captive pigtailed macaques are a significant predictor of reproductive success and the need for veterinary intervention.
• Behavioral monitoring offers a valuable tool for identifying at-risk pregnancies and optimizing management strategies in captive breeding programs.