Physiological and ecological consequences of sleeping-site selection by the Galapagos land iguana. ( Conolophus pallidus).

In the coolest season (garua), adult land iguanas were found in sleeping sites that were warmer than the coolest sites available. This may be because the garua season (cool, overcast, and foggy) is a time when environmental conditions mitigate against rapid warm- up in the mornings, so lizards may regulate nighttime body temperatures so that it is easier to warm up to preferred daytime body temperatures. In the warmest season, adult iguanas were found in the coolest sleeping sites available, consistent with hypotheses of voluntary hypothermia, which can be advantageous in energy conservation and in avoiding detrimental effects associated with maintenance of constant body temperatures throughout the day and night. Juvenile iguanas slept in rock crevices regardless of the ambient thermal environments. Such sites are likely to be important as refugia for this life stage which, unlike the adult stage, is vulnerable to predation. -from Authors