Implications of climate change for basking behaviour in a cool-climate lizard previously considered as nocturnal (#314)
Global analyses of the vulnerability of lizards to climate change often consider species by their activity period (diurnal versus nocturnal). For robust conclusions, such analyses depend on accurate information about activity periods. In the past, the viviparous, rock-dwelling gecko Woodworthia “Otago-Southland” from southern New Zealand (formerly Hoplodactylus maculatus) has often been categorized as nocturnal as it forages extensively at night. However, our group’s studies show this description to be incomplete. Field observations using time-lapse photography confirm extensive basking in direct sunlight, especially by females (Gibson, Penniket and Cree, BJLS in press). Laboratory studies confirm that basking is context-specific (dependent on the thermal benefits) and practised more by pregnant females than by non-pregnant females or males. When only a narrow shaft of radiation is available, pregnant females often bask “on toes”, raising the surface temperature of the abdomen, above the developing embryos, to 30°C or more while the body extremities remain much closer to the ambient temperature of 16°C. This species therefore exhibits diurnal and nocturnal behaviours in both field and laboratory situations, and it should be classed as diurno-nocturnal. Diurno-nocturnality is likely to be widespread amongst viviparous New Zealand geckos traditionally classed as nocturnal. If climate change leads to warmer air temperatures with no reduction in solar radiation, then basking by Woodworthia “Otago-Southland” (with its attendant risks of predation) may decline, leading to more exclusively nocturnal emergence. Further warming could be followed by a declining use of superficial rock slabs as retreats. However, if climate change leads to warmer temperatures but increased cloud cover, then effects on basking behaviour and on use of superficial retreats are more difficult to predict.