Page 118 - Emotions through the eyes of our closest living relatives- Exploring attentional and behavioral mechanisms

Chapter 5
individuals). This housing environment aims to mimic the natural social structure of orangutans in which they form temporary parties but no stable social groups. Some individuals were never housed together to avoid conflict (e.g., the two adult males). Focal‐animal sampling of 10 min sessions was used to score behavioral patterns including social behaviors (e.g., grooming, agonistic interactions, and sexual behaviors), locomotion (e.g., walking and climbing), and food‐associated behavior (e.g., foraging and feeding; ~18.5 hr per focal; see Table S2 for the ethogram). We used all‐occurrence sampling to record all yawning and self-scratching events of group‐ members in the subgroup of the focal animal for 165 hr in total (Altmann, 1974).
Observations were performed by one trained researcher from the visitor’s area in both indoor and outdoor enclosures. Due to the relatively low temperatures during the observation period, the orangutans were kept inside and as such most observations were performed in the indoor enclosures. The indoor enclosures were ~60 m2 in which observation conditions were excellent; the researcher had full view of the enclosure and its individuals as there were no big constructions blocking the line of sight. In addition, because subgroups had a maximum of five individuals, and because yawning and self-scratching could be considered ‘attention‐attracting’ behaviors (Demuru & Palagi, 2012), it was possible for the researcher to record all yawning and self-scratching events.
The following variables were recorded whenever a yawn or scratch occurred: (a) time of occurrence; (b) identity of the expresser; (c) identity of all possible observers (i.e., individuals that were within the same enclosure); (d) presence/absence of a contagious response (i.e., a congruent behavior) within 3 min following the last triggering event (i.e., a spontaneous yawn or scratch. We selected a 3 min window in line with other work, and because a longer window would introduce the chance of ‘self-contagion’, meaning your own yawns or scratches cause you to perform these behaviors again (Gallo et al., 2021)) ; (e) time latency in contagious response measured in seconds (s); (f) duration of self-scratching behavior (short; 5 s); (g) if the observer could see the triggering event or not, based on the facial direction of the observer; (h) estimated distance between the expresser and observer (10 m); and (i) the context in which the triggering event occurred, categorized as ‘tense’ or ‘relaxed’. The context categorization was based on the behavior of the expresser before and after the yawning or self-scratching behavior. Behaviors that indicated tension included display behavior (e.g., charging and shaking of climbing structures), high arousal vocalizations (long‐calls or kiss squeaks), or agonistic behaviors (direct aggression and chasing). Because we rarely observed agonistic interactions, we
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