Active space of a movement-based signal

Richard A. Peters, Christopher S. Evans

Research output: Contribution to conferenceAbstract


The Jacky dragon (Amphibolurus muricatus) visual display is composed of five distinct motor patterns delivered in an obligatory sequence: tail-flicks, backward and forward foreleg waves, a push-up and a 'body-rock'. In contrast to other communication systems, the introductory tail-flick is characterised by reduced signal intensity (average speed) but longer duration than subsequent motor patterns. Playback experiments confirm that duration is paramount for reliable detection, although the movement need not be continuous. This finding can be explained in terms of constraints on receiver attention, which must necessarily be divided among several functionally-important tasks. The tail flick may also reduce energetic costs and be less likely to compromise escape. A final possibility considers the property of active space (the distance over which a signal can be detected), which is determined by signal intensity, the signalling environment and the sensory characteristics of receivers. Here we test whether variation in the active space of display motor patterns may help to explain signal design. If the tail flick is used as an introductory component because it has the greatest efficacy in this role, then we predict that it should be visible over a greater distance and robust to variation in receiver orientation. We present the results of an experimental analysis of the active space of the Jacky dragon display components, examining the response probabilities of receivers to isolated tail-flicks, foreleg waves and the pushup/body-rock motor patterns as a function of angle and distance. The results suggest that these signals degrade predictably, thereby providing potential ranging cues, and are remarkably robust to variation in receiver orientation, so that efficacy is maximized in most potential signalling situations.
Original languageEnglish
Number of pages1
Publication statusPublished - 2007
EventAustralian Society for the Study of Animal Behaviour Conference (33rd : 2006) - Sydney
Duration: 20 Apr 200623 Apr 2006


ConferenceAustralian Society for the Study of Animal Behaviour Conference (33rd : 2006)


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