Signal Competition in Dynamic Visual Environments: Relative Conspicuousness of Social Displays in the Jacky Dragon (Amphibolurus muricatus)

Abstract

Selection for conspicuousness has been an important force on visual signal design. Although signal efficacy has been extensively studied in acoustic systems, few studies have examined this attribute in dynamic visual signals. Here, I simulated signal competition between Jacky lizards (Amphibolurus muricatus) by presenting the motor patterns (tail-flick, push-up body rock, and slow arm wave) in isolation that are typically used in social communication. Phase 1 used four digital video playback systems to present simultaneous animated display combinations on opposing monitors to a subject that was situated in the middle, and measured orientation towards the monitors and latency to respond. Phase 2 maintained the same set-up and simultaneous display combinations, but tested signal conspicuousness across three levels of visual noise (calm, typical, and windy) simulated by the movement of windblown vegetation in the background. The results suggest that the most conspicuous visual display is the tail-flick, followed by the push-up body rock, and the slow arm wave is the least conspicuous. Moreover, this relationship is robust across the full range of environmental wind conditions. No significant side biases in orientation to displays were detected, which suggested no lateralization in perceptual processes. Jacky lizard display motor patterns which address distinct functional requirements: the tail flick is an ideal alerting component, with high efficacy over a range of signaling conditions. The push-up body rock, which is used only in aggressive displays, has a more restricted range, and the submissive slow arm wave is likely designed to appease nearby dominant males.