concept

Gigantothermy

The temperature stability a very large body gets from geometry alone, without raising its metabolic rate. Surface area grows as the square of length while volume grows as the cube, so the bigger the body the lower its surface-to-volume ratio, and the slower its core responds to anything happening outside. A leatherback turtle can swim in near-freezing water where its smaller relatives cannot; large sauropods presumably did the same. It is why a multi-tonne animal can ignore an hour of cold - and equally why it cannot ignore a long chase.