RESUMO
Lizards that inhabit high-latitude alpine zones are exposed to extreme temperatures and long winters and most are diurnal heliotherms. Yet some poorly known nocturnal species exist in such locations, including several viviparous geckos from New Zealand. We studied the orange-spotted gecko (Mokopirirakau 'Roy's Peak'), a cryptic, nocturnal and viviparous lizard known only from the alpine zone (1150-1800 m a.s.l.) in the South Island (~44°S). Our field study investigated (1) the influence of female reproductive condition and sex on daytime body temperatures, including relationships with microhabitat rock temperatures, (2) the influence of temperature and other weather conditions on gecko emergence by night and day, and (3) the thermal microclimates available year-round to orange-spotted geckos. Building a better understanding of these lizards aids in species conservation efforts, for example in developing monitoring programmes, and provides insights into the evolution of thermal mechanisms in cold environments. Reproductive females maintained higher daytime body temperatures than non-reproductive females and males, suggesting pregnancy-related thermophily. On summer days, all reproductive groups reached similar body temperatures to New Zealand geckos from lower elevations, suggesting similar thermal preferences. Using trail cameras, we obtained evidence of geckos openly basking during the day (previously undocumented for this species) when temperatures of exposed lizard models (=Texp) were 3.2-39.3 °C. We also observed emergence at night at low Texp (-0.8-14.6 °C), when some Tbs were probably 0-6 °C. Diurnal activity increased as Texp rose to peak at ~30 °C before dropping again at higher temperatures, whereas nocturnal activity unexpectedly decreased with increasing Texp. Our study provides evidence of diurnal activity in a 'nocturnal' gecko that may be essential to squamate viviparity at high-latitude, high-elevation sites. It also suggests remarkable capacity for locomotor activity at extremely low Tb.
