MAINE SUNDAY TELEGRAM • June 2, 2024
Biologists commonly use comparative techniques to try to understand variation. Bergmann’s Rule says that birds and mammals that live in higher latitudes or higher elevations are generally larger in size than animals from lower altitudes or from temperate and tropical habitats. Allen’s Rule looks at the same gradient and predicts that the smaller body appendages like ears, tails, limbs, or bills should be smaller in arctic or montane species. Both rules can be explained in terms of heat loss. ~ Herb Wilson