Social hair pulling in captive rhesus macaques (Macaca mulatta)

Area of Science:

• Primate Behavior
• Veterinary Dermatology
• Animal Welfare

Background:

• Alopecia is a common issue in captive nonhuman primates, with diverse potential causes including environmental and behavioral factors.
• Social hair pulling, where one primate pulls another's hair, has been inconsistently classified as grooming or aggression in scientific literature.
• Understanding the specific behaviors contributing to alopecia is crucial for improving the welfare of captive primates.

Purpose of the Study:

• To investigate the characteristics of social hair pulling in group-housed rhesus macaques (Macaca mulatta).
• To differentiate social hair pulling from grooming and aggression.
• To determine the relationship between social hair pulling and the prevalence of alopecia.

Main Methods:

• Conducted weekly 30-minute behavioral observations over one year across seven groups of rhesus macaques (N=319).
• Recorded instances of social hair pulling, grooming, aggression, and dominance behaviors.
• Assessed individual alopecia severity monthly.

Main Results:

• Social hair pulling was predominantly directed downwards in the social hierarchy, unlike grooming which was directed upwards.
• Hair pulling rarely co-occurred with aggression, suggesting it is not a form of aggression.
• A significant correlation was found between the frequency of receiving hair pulling and the severity of alopecia.

Conclusions:

• Social hair pulling is a distinct behavior, separate from grooming and aggression, in rhesus macaques.
• This behavior is a significant contributing factor to alopecia in socially housed macaques.
• Findings highlight the need to address social hair pulling to improve captive primate welfare.