Theory 34/Geometry & Scale/Thermoregulation
Body Size Is a Heat Leak
The claim
A body's heat loss per unit mass is set by its surface-to-volume ratio, so small animals in cold climates are limited by geometry before they are limited by insulation.
01Mechanism
Heat leaves through the surface while it is generated throughout the volume; as size falls, the ratio rises and no amount of fur fully compensates.
02Prediction
Cold-climate body size should track the ratio across taxa.
03Refutation
Size limits tracking insulation quality would remove the geometric term.