Dragon wars: Movement-based signalling by Australian agamid lizards in relation to species ecology

Abstract

It is evident that the environment has the potential to affect animal communication strategies. Species from diverse taxonomic groups using signals from different modalities are known to generate signals that suit the structure of their habitat in order to maximize efficiency. Studies of acoustically communicating species dominate the literature, but visual signals are also tailored to local conditions. There is now increasing evidence that dynamic visual signals, in the form of movement-based displays, are also influenced by habitat characteristics. Australia's dragon lizards (Family: Agamidae) employ such dynamic signals in a variety of contexts but are particularly common in territory defence. With a few notable exceptions, the signalling behaviour of this group has been relatively overlooked, and the knowledge that does exist is contained in scientific papers focused on other topics or unpublished accounts from herpetologists. In this review, we collated information on the signalling behaviour of these animals and determined that 34 of the 78 species use movement-based signalling. This number is likely to be an underestimate, as knowledge of the signalling behaviour of many species is lacking. The richly contrasting environments of Australia inhabited by these lizards provide considerable variation in ecological context, so our second objective was to place known signalling behaviour in the context of species ecology. After controlling for phylogeny, we found that broad habitat classifications do not strongly influence the likelihood of motion signalling, and specific motor patterns are not more likely to occur in particular microhabitats. We conclude by suggesting that fully understanding the motion signalling behaviour of Australia's agamids will require documenting the displays of species for which there are no data, while taking into account the high variability existing within motor patterns and considering in detail the environmental context under which signalling takes place.