Heliotherms in tropical rain forest: the ecology ofKentropyx calcarata(Teiidae) andMabuya nigropunctata(Scincidae) in the Curuá-Una of Brazil

Kentropyx calcarata(Teiidae) andMabuya nigropunctata(Scincidae) occur together in lowland tropical forest of the Amazon near the Rio Curuá-Una of Brazil. During the wet season of 1995 these lizards were common at forest edge along narrow roads that transect forest, in treefalls and along streams where sun reaches the ground. Both species are heliothermic, basking to gain heat. Their association with open patches results from high activity temperature requirements in an environment where sun availability is low. Null temperature distributions from forest and treefalls showed that forest does not offer opportunities for heat gain similar to treefalls. Moreover, the large proportion of time spent basking by both species indicates the importance of these patches for thermoregulation.K. calcaratais slightly larger in body length and heavier at a given body length thanM. nigropunctata. Both species are active foragers that seek out prey while moving through the habitat, feeding on orthopterans, roaches and spiders.M. nigropunctataalso eat significant numbers of insects that occur on vegetation, such as hemipterans. Prey size is larger inK. calcarataand associated with lizard body size. Prey size does not vary with body size inM. nigropunctataand prey are typically relatively small. Many of the ecological differences between these two lowland forest species appear to be historical: the ecology ofK. calcaratais very similar to that of other species ofKentropyxand teiids in general and the ecology ofM. nigropunctatais most similar to that of other studied species of south AmericanMabuya.