Ecophysiological comparisons between two large Saharan lizards, Uromastix acanthinurus (Agamidae) and Varanus griseus (Varanidae)

Abstract

Physiological responses to environmental and experimental stimuli were measured in the herbivore Uromastix acanthinurus and the carnivore Varanus griseus. Differences in the thermal scales of the two species circumscribe their distribution within different desert habitats and their seasonal cycles of activity. Seasonal variations in the condition indices used are more pronounced in U. acanthinurus than in V. griseus. The water turnover rates of U. acanthinurus and V. griseus are very low and their variations are largely due to differences in behaviour, diet and seasonal conditions, but habitat separation occurs only in U. acanthinurus. The two species have a functional nasal gland. Nasal salt secretions (KC1 for U. acanthinurus, NaCl for V. griseus) are related to their diets, although U. acanthinurus can tolerate a higher plasma level of Na+ during the dry season.