What factors allow opportunistic nocturnal activity in a primarily diurnal desert lizard (Ctenotus pantherinus)?

Most animals show strong 24-h patterns of activity, usually being diurnal or nocturnal. An Australian desert skink, Ctenotus pantherinus, is unusual in being active day and night when all other Ctenotus species are diurnal, making it an excellent model to explore factors that promote night-time activity. We tested whether C. pantherinus 1) selects cooler temperatures than diurnal skinks, 2) shows no difference in mean selected temperature between day and night, 3) has the same metabolic rate during the day and night, 4) selects termites over other prey types, 5) can detect prey using only auditory or olfactory senses, and 6) experiences lower predation risk at night than during the day. C pantherinus shows many features of diurnal skink species, with a high mean selected temperature (36.1 +/- 1.6 degrees C) that is the same night and day, and a 32% lower metabolic rate at night than during the day. C. pantherinus selects termite prey over other insects and can detect prey using only auditory and olfactory senses; models of C. pantherinus experienced less predation at night than during the day. Preference for termites and reduced predation risk at night favour opportunistic nocturnal activity in this predominantly diurnal lizard and may contribute to its wide geographic distribution in arid Australia. (C) 2010 Elsevier Inc. All rights reserved.