Links between variation of movement-based visual signals and social communication complexity in Asian agamid lizard Phrynocephalus vlangalii

The social complexity hypothesis suggests that complex social interactions drive the evolution of sophisticated communicative signals. While sound and color signals have been widely studied, the role of social communication on movement-based visual signals remains less explored. In this study, we used the Asian agamid lizard Phrynocephalus vlangalii and investigated how social interactions influence the tail display behaviors in both males and females. Our experiments revealed that males significantly reduced the average tail coil duration during the mating season compared with non-mating season, while females increased both tail display duration and variation of tail coil amplitude in response to the demands of parental care. Additionally, tail display duration in females was positively correlated with reproductive investment. These results highlight the roles of social communication in shaping movement-based visual signals, providing novel support for the social complexity hypothesis from movement-based visual signals.