3 research outputs found
The structural and motivational role of the unique lipāflip movement in the gelada (Theropithecus gelada) facial display repertoire
ObjectivesHuman language represents an extreme form of communicative complexity. Primate facial display complexity, which depends upon facial mobility, can be used as a model for the study of the evolution of communicative complexity. The gelada (Theropithecus gelada) is the only primate that can produce a lipāflip eversion. This study investigates the role of the lipāflip relative to the baredāteeth display to understand its role in generating communicative complexity.Materials and methodsWe reviewed videos of gelada social interactions. We utilized the facial action coding system (FACS) to define structural component action units (AUs) of each display. We inferred display motivation from the behaviors of the display sender.ResultsThe lipāflip was used only in combination with the essential AUs of the baredāteeth display, serving as an optional structural element added to produce a structural variant. Both the baredāteeth display with and without a lipāflip occurred most frequently with nonaggressive, submissive behaviors. The lipāflip was more frequently preceded by approach than the baredāteeth display, especially in males. The lipāflip was also present in the majority of structurally blended facial displays though the motivation of the nonālipāflip parent display often dominated.DiscussionThe lipāflip may potentially function as an indicator of benign intent after an approach or as an intensifying component of nonaggressive intent. Adaptations to increase facial mobility in geladas via facilitating the lipāflip may promote increased communicative complexity through increased conspicuousness and motivational signaling specification or intensification.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155514/1/ajpa24031_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155514/2/ajpa24031.pd