THERMAL RELATIONS OF FIVE SPECIES OF TROPICAL LIZARDS

Abstract

The relation of a reptile's body temperature to that of the surrounding environment has been of considerable interest since the work of Cowles and Bogert (1944), and Bogert (1949a). These authors demonstrated that by behavioral methods reptiles were able to maintain their body temperature within a relatively narrow range. Reptiles, in other words, were shown to exhibit a degree of homeostasis in regard to their body temperature. The preferred or eccritic body temperature, was not the same for all the species studied. However, Bogert (op. cit.) demonstrated that lizards belonging to the same genus have similar body temperatures, while there may be marked differences between genera. Virtually all work reported for lizards has been with basking (heliothermic, Cowles, 1940) forms that gain heat from radiant energy. These heliothermic species raise their temperature above that of the surrounding air, and may achieve differences as great as 31 ? C between their body temperature and that of the surrounding air (Strelnikov, 1944; Pearson, 1954). With few exceptions (Inger, 1959; Bogert, 1949b) the species that have been studied are all temperate region forms, and actually the most intensively studied species have been from semiarid regions. In this investigation five Cuban species of the neotropical iguanid genus Anolis were studied in the field to determine their body temperatures and habitat temperatures. Two of the species were also studied in the laboratory to augment the findings in the field. The five species presented an opportunity to study thermal relations in tropical reptiles. As St. Girons and St. Girons (1956) emphasize, little is known about the thermal relations of tropical reptiles. The tropics represent the zone of the greatest abundance of species and individuals of reptiles. This abundance is in part attributable to the narrow temperature fluctuations of the lowand tropics where the temperature extremes of temperate and subtropical semiarid areas are never encountered. These five Cuban species represent an extraordinary example of habitat differentiation between closely related species in contiguous habitats. At the localities studied in central Cuba all five species are present, yet each is segregated in a specific ecological niche. As will be described below, the habitats range from the deep shaded portions of the forests, to the margins of the forests where filtered sunlight is present, to the open exposed habitats of the pastures and savannas.