Heat, safety or solitude? Using habitat selection experiments to identify a lizard's priorities

Laboratory experiments with a rock-dwelling nocturnal gecko, Oedura lesueurii, showed that retreat-site selection (and other behaviours) are affected by the interplay between thermal benefits, social advantages and avoidance of predators. Velvet geckos were highly selective in habitat choice: they preferred artificial retreat-sites that mimic the thermal properties of natural rocks in full sun rather than those that mimic rocks in full shade; mature male geckos rarely shared retreat-sites with other adult males; and these lizards strongly avoided retreat-sites covered with the scent of a natural predator (the broadheaded snake, Hoplocephalus bungaroides). After documenting these preferences, we carried out additional trials in which two or more of these factors co-occurred, as is often the case in nature. Social dominance interacted with thermal benefits in determining retreat-site selection, with smaller (subordinate) males forced to use cooler retreat-sites when larger (dominant) males were present. Avoidance of predators was a higher priority than thermoregulation: the lizards would forego a warmer retreat-site with predator scent in favour of a cooler, unscented one. There was also an interplay between social dominance and predator scent: smaller males were forced to use either predator-scented retreat-sites or no retreat-site when larger males were present. General activity levels, and the frequencies of specific behavioural acts, also shifted in response to social and predator-scent cues. Our study emphasizes the complexity of habitat-selection behaviour in these lizards, and clarifies the criteria used in retreat-site selection when (as is commonly the case) the animal must choose between conflicting priorities. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.