Ecology of the Gecko Gymnodactylus geckoides amarali in a Neotropical Savanna

Abstract

We describe the ecology of the gecko Gymnodactylus geckoides amarali in the Cerrado of central Brazil and using published data, compare it with the conspecific Gymnodactylus geckoides geckoides from the Caatinga of northeastern Brazil. Gymnodactylus geckoides amarali is rupicolous, living primarily in rock crevices in “campos rupestres” (rocky fields), which are highly patchy in Cerrado. Field body temperatures were low and associated with environmental temperatures, suggesting thermoconformity. Termites were the most important food item, and consumption was greatest during the dry season. We suggest that access to termites is facilitated by the shallow soils used by G. g. amarali and by its well-developed chemosensory apparatus. Reproduction was concentrated in the dry season, a pattern known for very few Cerrado squamates, possibly because of the higher availability of termites during that period. Clutch size was significantly correlated with female size, a pattern unknown in any other gecko, and there was no association between egg size and female size. Gymnodactylus geckoides amarali produced larger clutches of smaller eggs relative to G. g. geckoides, presumably because of the high climatic unpredictability of the Caatinga. We detected a significant sexual dimorphism in both body size and shape: females were larger and had smaller heads than males. We suggest that large female size is likely a plesiomorphic character of gekkonids and that large head size in males results from sexual selection theory.