Variation in field body temperature and total evaporative water loss along an environmental gradient in a diurnal ectotherm

Abstract

The maintenance of optimal body temperatures has profound consequences on all aspects of ectotherms life history, like fitness and performance, and has been the subject of research for decades. In contrast, for reptiles, comparatively less is known on the potential effects of water balance on physiology, ecology and behaviour. In recent years, several recent studies are pointing out the importance of studying thermoregulation and water balance within the same framework. Here, we used a Mediterranean lizard, Psammodromus algirus, to investigate how field body temperature and water loss rates may vary among populations, between sexes and along an altitudinal gradient. We found little variation in field body temperatures among populations, while within each population, field body temperature may change daily, seasonally and differ between sexes. On the contrary, water loss rates decreased with elevation and showed no seasonal trend or difference between sexes. Microclimatic data indicated that highland lizards experienced more fluctuating conditions, a factor that may explain their lower water loss rates. Other factors, like inter-population differences in ectoparasite intensity, might also contribute in explaining the observed patterns. We present here the first data for a lacertid lizard on the inter-population variability and sexual difference in water loss rates and point out that water balance may play a fundamental role in regulating lizard activity during the hottest and driest period of the year.