Ontogenetic shifts in risk behaviours are related to body size and coloration in spiny-footed lizards

Abstract

Ontogenetic colour changes in animals generally involve cryptic juveniles developing conspicuous coloration when they achieve sexual maturity. However, there are several species in which juveniles develop conspicuously coloured tails that become cryptic in adults. In lizards, colourful tails may act as an antipredator mechanism, either by diverting predator attacks from vital body parts to the expendable tail (decoy hypothesis) or, when associated with tail movements, by signalling to the potential predator that it has been spotted and an attack will probably not succeed (pursuit deterrent hypothesis). In both cases, the antipredator function would allow lizards with colourful tails to show more risk-taking behaviours. The aim of this study was to test whether conspicuous coloration was related to risk behaviours in spiny-footed lizards, Acanthodactylus erythrurus, a species with red-tailed juveniles. Behaviour was recorded in free-ranging lizards and several risk-related behavioural indices were calculated. As predicted, risk behaviour and tail coloration were found to be related, as redder (less orange) lizards stayed further from refuge, maybe because redder coloration was associated with a perception of lower predation risk. Coloration was not related to any other behavioural index, including tail displays, but the level of activity was negatively related to lizard size, suggesting a change towards less active behaviour associated with growth, probably because energy and thermoregulatory requirements depend on body size. In conclusion, the link between red coloration and risk-taking behaviour in spiny-footed lizards supports the antipredator function of this coloration that enables more colourful lizards to take more risks when necessary. Moreover, the nonsignificant association between coloration and tail displays is not consistent with the pursuit deterrent hypothesis, thus making the decoy hypothesis more probable.