BEHAVIORAL ECOLOGY OF TROPIDURUS-HISPIDUS ON ISOLATED ROCK OUTCROPS IN AMAZONIA

A population of the tropical lizard Tropidurus hispidus, isolated on a granitic rock outcrop in tropical forest of northern Brazil, was stud ied during the 1993 wet season. Four types of observational studies re vealed that lizards are active throughout most of the day. During 10-m inute intervals, individual lizards moved five times for an average of 240 cm and tongue-flicked once. Habitat temperatures vary considerabl y during the day, with rock and air temperatures in sun exceeding body temperatures of lizards during much of the activity period. During mo st of the day, lizards thermoregulate by moving among shady, filtered sun, and sunny microhabitats maintaining body temperatures near 35 deg rees C. Temperatures of lizards active during cloudy periods were sign ificantly lower than temperatures of lizards during sunny periods, ind icating that clouds decrease the ability of lizards to effectively the rmoregulate. Most feeding occurs in the afternoon at edges of rock out crops with ants, insect larvae, termites and beetles dominating the di et. Comparisons with a near-by savanna population revealed differences in body size (males only), activity period (longer on rocks), body te mperatures (higher on rocks), number of prey categories consumed (lowe r on rocks), mean size of prey (larger on rocks), number of prey eaten (fewer on rocks) and microhabitat use (more restricted on rocks).