Peters RA & Evans CS (2003) Introductory tail-flick of the Jacky dragon visual display: signal efficacy depends upon duration. Journal of Experimental Biology, 206, 4293-4307.
Many animal signals have introductory components that alert receivers. Examples from the acoustic and visual domains show that this effect is often achieved with high intensity, simple structure, and short duration. Quantitative analyses of the Jacky dragon (Amphibolurus muricatus) visual display reveal a different design: the introductory tail-flick has a lower velocity than subsequent components, but longer duration. Here we use a series of video playback experiments with a digitally animated tail to identify the properties responsible for signal efficacy. We began by validating the use of the computer-generated tail, comparing responses to digital video footage of a lizard tail-flick with those to a precisely matched 3D animation (Experiment 1). We then examined the effects of variation in stimulus speed, acceleration, duration and period by expanding and compressing the time scale of the sequence (Experiment 2). Results identified several variables that might mediate recognition. Two follow-up studies assessed the importance of tail-flick amplitude (Experiment 3), movement speed, and signal duration (Experiment 4). Lizard responses to this array of stimuli reveal that duration is the most important characteristic of the tail-flick, and that intermittent signalling has the same effect as continuous movement. We suggest that signal design may reflect a trade-off between efficacy and cost.
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