DEPENDENCY OF SURFACE-TEMPERATURE REGULATION ON BODY-SIZE IN TERRESTRIAL MAMMALS

1. Infrared scans were taken of 29 mammal species ranging from 20 g wh ite-footed mouse to 4000 kg African elephant and percent of surface ar ea available for heat exchange determined. 2. An index of vasomotion ( VMI) which reflects the animal's dependency upon and ability to contro l surface temperature was created by combining metabolic output, therm al limits, and effective surface area (ESA). 3. VMI scales positively with body weight by the equation VMI = 0.27717 + 0.27929 log(wt) sugge sting the ability to control surface temperature becomes increasingly more important as surface area to volume ratio decreases. 4. A value f or functional conductance was calculated using part of the same VMI eq uation. Values ranged from 1.453 to 6.15 W/m(2)/C with no apparent cor relation to weight. 5. Functional conductance considers only those sur faces which are available for regulation of heat exchange and is essen tially the same for all animals studied, indicating heat is conducted from bare skin at the same rate in all animals. 6. It is the ability t o change the ESA which causes the VMI to scale by weight.