Appendix 2: Ethogram

This ethogram was developed during a pilot study on Cayo Santiago in the summer of 1996 and owes much to previously published ethograms by Altmann (1962), Hinde & Rowell (1962) and Bernstein & Ehardt (1985b) for affiliative and agonistic behaviour, Dixson (1998) for sexual behaviour and van Hooff (1962) and de Waal & Luttrell (1985) for descriptions of facial and gestural signals.

1. Affiliative activities or interactions

Affiliation has been observed in different behavioural contexts, but only the first three listed below have been systematically analysed.

(i) Activities

Sharing spatial proximity: All neighbours within the 5m radius were identified with their exact distance (in m) towards the focal female including their activities at a time. These data, in contrast to all others, are based upon point samples (see Methods).

(ii) Interactions

Grooming: Picking through fur or over the skin of another individual, using hands and/or mouth. This behaviour was not scored unless a minimum duration of 5 seconds was achieved.

Friendly approach: Approach of an individual ranging from body contact up to 2.0m, the approaching individual had to remain within the 2.0m range for at least 5 seconds. This approach was followed either by an affiliative interaction or by sitting close to each other (sharing spatial proximity).

Co-feeding: Sharing a high quality food resource by tolerating each other in body contact while feeding chow on a chow container.

Co-drinking: Sharing a limited resource by tolerating each other in body contact while drinking from a water tank.

Lipsmack: Facial expression produced by protruding and rapidly moving the lips up and down, without opening the mouth. Most often given during initiation or maintenance of peaceful contact.

Girney: Soft, low-pitched, quavering and rather nasal vocalisation during the initiation and maintenance of affiliative interactions.

Low grunt: Low amplitude, pulsed, hoarse and breathy call, typically given when one individual approached or is approached by another.

2. Agonistic interactions

This section summarises different agonistic interactions, such as agonistic approaches, non-physical or physical aggression and submissive agonistic interactions. Patterns of aggressive behaviour are presented in the order of increasing intensity, acts with higher intensity were often used in conjunction with less severe gestures. Thus, in prolonged bouts only the kind of aggression with the highest intensity was used for the analyses. Aggression is distinguished as non-physical (lacking body contact between opponents) and physical events (with body contact between opponents). If physical as well as non-physical aggression was exhibited in the same bout only the physical aggression was counted. The term fight was used to describe prolonged incidents involving bidirectional grabbing and/or biting.

(i) Agonistic approaches

Approach-avoid: Approaches directed towards a recipient, who left when the approaching individual reaching a distance between 1 and 2 m. This response was interpreted as a choice to leave in order to avoid a conflict.

Approach-displace: Approaches directed towards a recipient, who had been displaced by the approaching individual reaching a distance closer than 1 m. This response was interpreted as the leaving animal was forced to leave.

(ii) Non-physical aggression

Stare: fixed staring towards a recipient combined with brow-raising and ears flattened back.

Head-bobbing: includes stare while the head is moving forward.

Open mouth threat: open mouth without seeing the teeth usually combined with stare and head-bobbing.

Slapping on the ground: slapping the ground with one hand, accompanied with one type of aggression mentioned before.

Vocal threat: hoarse, low-pitched pulsed call, produced with rounded and protruded lips, often directed several times in quick succession, accompanied with stare and open mouth threat, intensity varies from grunts to barks, sometimes as an aggressive scream.

Lunge: rapid aggressive movement toward another individual at a close distance, usually accompanied by a vocal threat.

Charge: pursuit of an individual for less than 5 metres, recipient may avoid, fear grin or flee.

Chase: running pursuit of an individual for more than 5 metres, assumes that the recipient flees.

(iii) Physical aggression

Push: manual contact aimed to remove the recipient out of way, including pushing the recipient or pulling its tail.

Hit: slapping the recipient.

Grab: aggressive manual contact, likely to cause discomfort without injury to the victim.

Bite: single bite, with or without holding down of recipient.

Attack: sustained and/or repeated bites lasting for more than 5 seconds, often involving head-shaking or slashing with the canines and typically performed whilst pinning down the victim.

(iv) Agonistic interactions (submissive response)

Fear grin: Facial display in which the lips are retracted so that clenched teeth are exposed, given in response to another animal.

Scream: Loud, highly pitched, often harsh sounding calls of prolonged duration or less intense as a squeal.

Flee: Rapid withdrawal from another individual.

3. Interventions in conflicts (Coalition formation)

A coalition is formed when an animal intervened in an ongoing dyadic conflict between two parties in order to support one of them. Depending on the role in this interaction, one distinguishes between the supporter, who intervenes and supports one party, the recipient, who receives the support, and the target, against whom the coalition was formed. Since support in favour of one party is simultaneously targeting the other party, coalitions are triadic interactions involving a supporter, a recipient and a target. This behaviour pattern will separately analysed, as it simultaneously contains a co-operative interaction (support in favour of a recipient) and a competitive interaction (support against a target). Instances where two individuals simultaneously and jointly commence aggression against a third were not considered (more details in Methods).

4. Other activities or interactions

All behavioural pattern listed below are rather neutral activities or interactions with respect to the topic of interest.

(i) Activities

Locomotion: Travelling over longer distances e.g., as a consequence of group movement.

Rest: Stationary and clearly relaxed, with eyes open.

Sleep: Stationary with eyes closed, slow and regular breathing.

Forage: Preparing or ingesting any naturally occurring food item, including vegetation, digging and eating soil from habitually used dips in the ground, searching for and consuming small invertebrates. The type and part of the matter ingested would additionally be specified.

Drink: Drinking water from a fountain or pool, or licking rainwater from leaves or small crevices. The source was specified.

Self-scratching: A usually repeated movement of hand or foot, during which the digital tips are rapidly raked across the individual's hair or skin. This behaviour may indicate insecurity.

Yawn: Performed in a variety of contexts, including when resting or falling asleep, in tense situations.

Self-grooming: Picking through the own hair or skin. This behaviour was not scored unless a minimum duration of at least 5 seconds was achieved.

(ii) Interactions

Muzzle up: Puckering facial expression made by males when approaching and soliciting copulation from females.

Genital inspect: Olfactory, oral or manual examination of another individual's genital area.

Sexual present: A display in which a standing female presents her hindquarters to a male.

Sexual mount: Alignment of the male's hindquarters with the haunches of the female, and with the actor's feet either grasping the recipient's calves or remaining on the ground.

Present: Orienting the hindquarters toward another individual. Recipient can often be used to distinguish submissive and affinitive versions from sexual presents, together with the context in which the act is performed.

Ignore: To fail to respond to another’s affiliative or agonistic overtures in situations where the actor appeared fully aware of the latter.

Social play: Interaction as chasing games, chase or fight, but during relaxed circumstances, lack of ritualised agonistic signals, often involving a play face.