Experimental analyses of an agamid lizard display: signal efficacy depends upon duration

Many animals 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 revealed that introductory tail-flicks have lower velocities than subsequent components, but longer durations. In a series of video playback experiments with digitally animated tails, we explored tail-flicks efficacy in terms of the trade-off between intensity and duration. We began by validating the use of the animated tail by comparing responses to digital video footage of a lizard tail-flick with those to a precisely matched 3D animation. We then examined the effects of variation in stimulus velocity/acceleration, by expanding and compressing the time scale of the sequence. Results identified several variables that might mediate recognition. Two follow-up studies assessed the importance of tail-flick amplitude, movement speed, and signal duration. Lizard responses to this array of stimuli reveal that duration is the most important characteristic of the tail-flick, an that intermittent signaling has the same effect as continuous movement. We suggest that signal design reflects a trade-off between efficacy and cost.1 page(s