Relative Effects of Size, Season and Species on the Diets of Some Amazonian Savanna Lizards

Abstract

The foods taken by Ameiva ameiva, Cnemidophorus lemniscatus, Kentropyx striatus, and Anolis auratus in the Amazonian savanna at Alter do Chao depend more on the species of lizard than on lizard size. Lizard size affects the size of food items but this has relatively little effect on the types of foods eaten. The effect of body size appears to be similar for both stationary vegetable foods (fruits), and for the total diet, which consist mainly of invertebrates. The occurrence of vertebrates in the diet of the teiids is much less than for the same species in a seasonally inundated Amazonian savanna. Diet may vary among species of lizards be- cause they differ in size, use different habitats, or because they differ in foraging behavior (Toft, 1985). Competition is often inferred as the ul- timate cause of these differences but evolution- ary hypotheses are difficult to test. Questions about proximal mechanisms are also difficult to analyze statistically. It is possible to test for any difference among the diets of an assemblage of lizards but this question is usually trivial. The null hypothesis is that the lizards have inde- pendently evolved exactly the same diet. This possibility is sufficiently remote that the rejec- tion of the null hypothesis is simply a question of sample size. Questions about communities are more profitably examined as the relative