Affiliative Behaviors (from Hall 1966 unless otherwise noted)
- Allogroom, both genders and all ages groom other group members (Nakagawa 1992)
- Commonly observed, similar to that of baboons
- Peak activity in morning, though observed throughout the day's resting period
- Approaching, followed by close sitting is often an invitation for grooming
- Males rarely groom or receive grooming
- Groom c. 96% less frequently than females
- Receive < 10% of all grooming observations
- Infants groomed by nearly all adult females
- Co-sleep
- "Kiss"; observed in wild and individuals in managed care
- One individual approaches another, stretching the head forward so that its mouth touches that of the other
- Sometimes precedes grooming
Play (from Hall 1966 unless otherwise noted)
- Infants (aged 3 to 12 months) and juveniles
- Frequently play for long periods, up to 30 minutes; no parallel in other terrestrial monkey
- Prevalent during morning (up to 10:00)
- Often in groups of 6 or more juveniles
- Bounce, chase, and wrestle; on the ground most often
- Bounce alone or as an invitation to chase
- Up and down, in the same spot; hopping quickly from hands to feet and back, continually; limbs held straight
- Often with apparent high-speed enthusiasm
- Alone; may run, full speed toward a bush, throwing the body sideways before making contact with the hands and feet; catapulting off and galloping away
- Full speed sprints over open ground
- Spar and wrestle; opponents stand on hind legs and face one another
- Grapple with hands around shoulders and arms
- Slap with hands
- Mouth held open
- Mock-biting
- Few observations of playing with or manipulating non-food objects
- Adult females occasionally play with juveniles or their infants
Aggression (from Hall 1966 unless otherwise noted)
- Rare, only 49 episodes observed during the course of one 627 hours observational study
- Aggression by one most often met by the rapid retreat of another
- Followed by counter-threat on occasion
- Chase distances typically < 50 m
- Physical contact uncommon
- c. 20% of aggressive interactions; brief biting without inflicting visible wounds
- Little or no vocalization during aggression
- Associated most commonly with 3 social situations
- Rough play by a juvenile or young adult with an infant; mother directs threat-attack
- Feeding areas with dense, clustered foods or those with a sought-after food resource (e.g. mushrooms)
- Reproductive interest and/or copulation
- Male may threaten others that come near a female of interest
- Group members (adult females and some young adults) harass the adult male during copulation attempts; including open-mouthed threats, lunges, and hitting or touching the male's face (Carlson and Isbell 2001; Hall 1966)
- Threat displays
- Yawn; known as a threat-yawn, displays large canine teeth
- Stare; fully facing opponent with a directed prolonged gaze, mouth held open with head slightly lowered
- Slap; strike out with a hand toward another
- One or two quick movements, most often
- Striding quickly toward another
- Fighting brief
- Bite, typically a brief nip
- "Surprise" attack; individual pounces on the back of another and delivers a quick bite
- Grapple
- Male group leaders rarely initiate attacks on group members