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

Area of Science:

• Primate social behavior
• Animal welfare science
• Veterinary medicine

Background:

• Captive rhesus macaque social groups exhibit predictable trauma patterns.
• Factors like group composition and dominance hierarchies influence trauma.
• Understanding these dynamics is crucial for improving animal welfare.

Purpose of the Study:

• To investigate how breeding season, matriline number, and matriline size affect socially induced trauma in rhesus macaques.
• To identify specific social and temporal factors exacerbating trauma in captive groups.

Main Methods:

• Analysis of 3 years of veterinary admittance logs from four specific pathogen-free (SPF) rhesus macaque groups.
• Comparison of trauma rates across different seasons, group formation times, matriline compositions, and dominance ranks.

Main Results:

• Trauma rates were significantly higher during the fall breeding season compared to spring and summer.
• The most recently formed group, with more matrilines but fewer related individuals, showed higher trauma rates.
• Lower-ranking matrilines experienced significantly more trauma than higher-ranking ones.
• A negative correlation existed between adult female numbers per matriline and trauma rates within that matriline.

Conclusions:

• Trauma in captive rhesus macaques increases during the breeding season, particularly in recently formed groups with smaller matrilines.
• Reduced social support and rank-related aggression contribute to higher trauma rates.
• Management strategies should focus on ensuring adequate matriline size to reduce trauma and improve welfare.