Evaluating Temperature Regulation by Field-Active Ectotherms: the Fallacy of the Inappropriate Question
Vol. 142, No. 5 The American Naturalist November 1993 EVALUATING TEMPERATURE REGULATION BY FIELD-ACTIVE ECTOTHERMS: THE FALLACY OF THE INAPPROPRIATE QUESTION *Department of Biological Sciences, Barnard College, Columbia University, New York, New York 10027; $Department of Zoology NJ-15, University of Washington, Seattle, Washington 98195; $Department of Biology, University of Massachusetts at Boston, Boston, Massachusetts 02125 Submitted March 16, 1992; Revised November 9, 1992; Accepted November 20, 1992 Abstract.-We describe a research protocol for evaluating temperature regulation from data on small field-active ectothermic animals, especially lizards. The protocol requires data on body temperatures (T,) of field-active ectotherms, on available operative temperatures (T,, "null temperatures" for nonregulating animals), and on the thermoregulatory set-point range (pre- ferred body temperatures, T,,,). These data are used to estimate several quantitative indexes that collectively summarize temperature regulation: the "precision" of body temperature (vari- ance in T,, or an equivalent metric), the "accuracy" of body temperature relative to the set-point range (the average difference between 7, and T,,,), and the "effectiveness" of thermoregulation (the extent to which body temperatures are closer on the average to the set-point range than are operative temperatures). If additional data on the thermal dependence of performance are available, the impact of thermoregulation on performance (the extent to which performance is enhanced relative to that of nonregulating animals) can also be estimated. A sample analysis of the thermal biology of three Anolis lizards in Puerto Rico demonstrates the utility of the new protocol and its superiority to previous methods of evaluating temperature regulation. We also discuss several ways in which the research protocol can be extended and applied to other organisms.
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