Efficiency of aggressive and submissive visual displays against environmental motion noise in Jacky dragon (Amphibolurus muricatus)

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Despite variations of environmental noise, signals are designed to be effective and conspicuous over an appreciable distance. In particular, visual signals must be perceptible against interference caused by natural elements, such as windblown vegetation. We examined the efficiency of aggressive and submissive displays to elicit behavioural responses from observers in the Jacky dragon (Amphibolurus muricatus) across relative environmental noise. Both displays have been reported to play an important role during social interactions in this species. We conducted two video playback experiments that utilised a high-resolution computer-generated lizard animation to produce social displays that were embedded within simulated windblown vegetation. First, we compared the efficiency a full aggressive display action pattern (comprised of a tail-flick, backward-forward arm wave, and push-up body rock) to a slow arm wave submissive display, against identical background of windblown vegetation. Second, we compared the tail-flick (alerting component) to the slow arm wave across three varying natural conditions, in which the vegetation behind the displays acted as simulated noise: calm, typical, and windy. We found that aggressive displays were more efficient to elicit an observer's response than submissive signals. Furthermore, the tail-flick display is more efficient than submissive displays across a range of natural variation in windblown vegetation movement, but both signals remain efficient in the face of environmental motion noise. Our results suggest that constraints from the environmental background scene play may have a critical role in the evolution of signal design used in Jacky dragon communication.