Size-dependent heating rates determine the spatial and temporal distribution of small-bodied lizards

Abstract

Abstract The rate of heat exchange with the environment is of obvious importance in determining the time budget of behavioural thermoregulation in ectotherms. In small reptiles, heating rate depends mainly on their physical characteristics. We analysed the effect of body size, and the possible joint effects originating from shape and colour differences on heating rate in three small-bodied (0.15-20 g) sympatric lizard species. Heating rate was strongly influenced by body size, while no joint effects with the two other factors were detected. We found that the increase in heating rate with decreasing body size accelerated dramatically below a body weight of 2-3 g. We also analysed associations between body size, seasonal activity patterns and thermal characteristics of the sites where lizards were encountered in the field. Differently sized lizards occurred in thermally different sites and differed in their seasonal activity patterns, both within and among species. Smaller (<2-3 g) lizards occurred in cooler sites and exhibited very low activity during summer. Our results suggest that body size has a considerable influence on the spatial and temporal distribution of extremely small lizards in environments subject to a danger of overheating.