ENDOTHERM ENERGETICS - FROM A SCALABLE INDIVIDUAL-BASED MODEL TO ECOLOGICAL APPLICATIONS

We outline a computer model of heat and mass transfer through flesh, f at and porous fur for endotherms of any dimensions. We then validate i t with a series of laboratory studies. Finally, we explore application s of the model to Bergmann's rule, predicting the mouse-to-elephant cu rve, climate-disease-toxicant interactions, animal 'design' via geneti c engineering and energetic constraints on community structure. As a f irst test of the model we present calculations and metabolic chamber m easurements for mammals ranging in size from mice to Holstein calves. We then compare simultaneous measurements on deer mice, Peromyscus man iculatus, of oxygen consumption, doubly labelled water turnover and fo od consumption with calculations of metabolic rate using body temperat ure radio-telemetry as input to the endotherm model. The endotherm mod el derived in the Appendix requires data on allometry (body dimensions , surface area), fur properties, core temperature, air and radiant tem peratures and wind speed. The model is useful for calculating energeti c expenditure in different microclimates without the need for extensiv e physiological measurements in the laboratory. Model predictions of m etabolic rate at 12-degrees-C and at 22-degrees-C were well correlated with each of the three empirical estimates. The model shows that the posture an animal assumes can influence measurements of metabolic rate . Model calculations of metabolic rate using postures ranging from a c urled-up ball-like geometry to a sprawled-out, cylinder or ellipsoid g eometry bracket all three sets of simultaneous empirical data taken on the same animals. Applications of the model show that it can be appli ed in a wide variety of circumstances to gain insight into physiologic al and ecological problems.