Opponent assessment in lizards: examining the effect of aggressive and submissive signals

During conflict, males often assess their opponent's fighting ability and motivation via dynamic signals. We conducted an interactive video playback study using male Jacky dragons, Amphibolurus muricatus, to determine which signalling strategy was the most effective at deterring aggression and eliciting submission. A 3D computer-animated lizard was used to present aggressive signals (push-up displays) and submissive ones (slow arm-waves). This approach reproduced natural display motor patterns precisely while controlling variation in morphology. Treatments all commenced with the stimulus lizard producing bouts of push-ups, but then diverged after the subject lizard's responses, according to predetermined rules. Lizards attacked the stimulus more frequently when it responded to submission with slow arm-waves, revealing that their behavior during a contest is sensitive to social contingencies. Individuals that signal submission without retreating are likely to incur a receiver retaliation cost. In addition, assessment processes are surprisingly sophisticated, involving the monitoring of both an index signal (push-ups) and a conventional one (slow arm-waves) during a single interaction. Copyright 2008, Oxford University Press.