Structure and function of visual displays produced by male jacky dragons, Amphibolurus muricatud, during social interactions.

Many lizards produce visual displays to mediate social behavior. However, most studies have focused upon displays used by iguanid lizards. We investigated and quantified the displays used by jacky dragons, an agamid lizard from southeastern Australia. By establishing male jacky dragons within individual territories and conducting experimental presentations of male and female intruders, we were able to demonstrate that territorial male Amphibolurus muricatus utilize a fixed action pattern display comprising discrete motor components to indicate territoriality and aggression. Displays directed to intruders contain an extra introductory component and modifying postural elements, whereas non-directed displays given in the absence of intruders lack these features and appear to be used to advertise territory ownership. Although the sequence of display components remained the same across non-directed, male-directed and female-directed displays, resident males differed in pushup duration and the number of pushups per display in relation to individual body size. This display variance might function to provide an honest signal revealing the body size or the physical condition of each individual, permitting opponents to assess each other effectively through their displays. Visual signals produced by intruding lizards were qualitatively distinct from the displays given by residents, and appear to indicate submission. However, male and female intruders differed in the frequency with which each type of submissive gesture was performed, implying that this might convey intruder sex.