On the Physiological Significance of the Preferred Body Temperatures of Reptiles

Abstract

The thermal relations of reptiles have been extensively analyzed in both field and laboratory during recent years (see Schmidt-Nielsen and Dawson, 1964; Brattstrom, 1965; Mayhew, 1968; Templeton, 1970). Although fundamentally Poikilothermie, many of these animals behaviorally achieve some control of their body temperatures during activity. Such behavioral thermoregulation primarily involves basking, postural adjustments, and use of favorable microclimates. This form of regulation is supplemented in certain instances by evaporative cooling (see, e.g., Templeton, 1960; Cott, 1961; Dawson and Templeton, 1963, 1966; Case, 1972; Crawford, 1972), vasomotor responses (see, e.g., Bartholomew and Tucker, 1963, 1964; Bartholomew et al., 1965; Bartholomew and Lasiewski, 1965; Morgareidge and White, 1969a, 1969b; White, 1970; Weathers, 1970, 1971; Weathers and White, 1971; Spray and May, 1972), changes in reflectance (Atsatt, 1939; Norris, 1967; Porter, 1967; Porter and Norris, 1969), and muscular thermogenesis (Hutchison et al., 1966; Vinegar et al., 1970). Combinations of behavioral and physiological responses allow various reptiles during activity under favorable circumstances to maintain body temperature within a preferred range characteristic of the species. This range may be relatively low in animals such as the rhynchocephalian Sphenodon punetatus and the gecko Phyllurus milii (Brattstrom, 1965; Lichtet al., 1966b) to relatively high in various heliothermic lizards (Licht et al., 1966b; DeWitt, 1967; Kemp, 1969).