Factors affecting retreat-site selection by coppertail skinks (Ctenotus taeniolatus) from sandstone outcrops in eastern Australia

Coppertail skinks (Ctenotus taeniolatus) are medium-sized diurnal lizards that are widespread in eastern Australia. Field surveys on sandstone outcrops in the Sydney region showed that these animals use available rocks non-randomly: coppertails were found under large, sun-exposed rocks on deep soil. Choice trials in the laboratory documented selection of retreat sites that were warm, with substrate preferences shifting in a diel cycle. Lizards selected retreats with rock substrates during the day but with sandy substrates at night. Rocky retreats attain higher temperatures during daylight hours, but burrows in sand beneath rocks may provide greater protection against ingress by nocturnal predators. During fieldwork we rarely found lizards under rocks with either ants or centipedes, suggesting that coppertails may avoid these predatory invertebrates. Tongue-flick trials showed that the lizards could discriminate among common ant species based on chemosensory cues, but apparently could not detect centipede chemical cues. In experimental trials, the lizards did not avoid retreat sites scented by either ants or centipedes. Our data thus suggest that retreat-site selection in coppertails is driven by abiotic cues (rock size, sun exposure and substrate type) that may confer fitness benefits in terms of thermoregulation and predator avoidance, with biotic cues playing a less important role.