A series of simple heat-transfer models (termed the basic, conduction, physiological, and wet-skin models) is derived to examine a large number of behavioral and physiological mechanisms that are used by terrestrial ectotherms to control body temperature (Tb; table 1). The models reaffirm two generalizations: (1) in environments where solar radiation is available, behavioral mechanisms may provide a range of Tb's that is many times greater than the range in Tb's that results from physiological adjustments; and (2) among behavioral mechanisms, the times of seasonal and daily activity appear to be the most critical in determining Tb. Furthermore, microhabitat selection is more important than postural adjustments for controlling Tb. The models calculate Tb as the sum of air temperature (Ta) and the body-air temperature difference (Td). The direct effects of body size are expressed as functions of Td. Many behavioral mechanisms can then be expressed as some fraction of Td. The models (eqs. 3, 6, 8, 11), in combination with table 2 and the Smithsonian tables (List 1966), allow one to quickly estimate the effects of many environmental variables and behavioral and physiological mechanisms on Tb.
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