Measurement and Application of Operative and Standard Operative Temperatures in Ecology

Operative and standard operative temperatures (Tc and Tcs, respectively) are thermal indices that allow single-number representations of the complex thermal environment. They can be measured directly using various physical models of the animal of interest. These models explore the thermal environment at the same spatial scale that the animal experiences, and can be replicated relatively easily to measure conditions at multiple sites. Thus, they offer a complementary approach to elaborate computer models, and have proven valuable in integrating biophysical and population ecology This workshop paper is primarily a summary and critical review of the uses and measurement of Tc and Tcs. I first review the principles behind Tc and Tcs. I then describe the various methods used to construct Tc and Tcs “thermometers,” and discuss their relative merits for various classes of animals and types of studies. Finally, I review typical applications. The most important is in mapping the nanoclimate experienced by small animals and in defining indices of thermal quality of home ranges based on such maps. Others include use as null models in physiological studies, and use as single-number descriptors of complex thermal environments in behavioral, physiological, and energetics studies.