Behaviour 2019
Where is lipsmacking oriented at? A study in wild capuchin monkeys (Sapajus libidinosus)
Marina Camargo, Natalia Albuquerque, Ana Clara Varella, Patrícia Izar. University of São Paulo, São Paulo, São Paulo, Brazil

Across a wide range of primate species, a commonly observed behavior is lipsmacking (LS), often described as an affiliative face-to-face interaction. Still, LS lacks understanding especially concerning its function. We studied this behavior in bearded capuchin monkeys, investigating where in the receivers’ body LS is directed at and whether the emitter seeks for eye contact when executing this behavior. We used 94 LS events from naturalistic videos of four focal two-month-old individuals and conducted a frame-by-frame coding analysis of the emitter’s head orientation (towards the infant’s face, head, hand, other parts, not the infant) and active seeking for the face (seeking or not seeking). We found that LS emitters spent significantly more time directed at the infant’s face than at any other direction. Also, seeking behavior lasted significantly longer than not seeking, which indicates that the emitter of LS is motivated to establish visual contact. However, LS did occur towards parts other than the face. These results suggest that, even though the face is critical, the function of LS may not be limited to face-to-face interaction.