According to the principle of German biologist Karl Bergmann, warm-blooded animals living in cold climates tend to be ... bigger? or smaller?... than animals of the same species living in warm climates.

It's a fascinating principle of nature first observed by 19th-century German biologist Karl Bergmann. He noticed that for many warm-blooded species, from bears to deer, individuals living in colder, higher-latitude environments tend to have a greater body mass than their counterparts living in warmer, more tropical climates. This pattern, now known as Bergmann's Rule, is a powerful example of evolutionary adaptation.

The scientific reasoning boils down to a simple principle of geometry: the relationship between surface area and volume. An animal generates heat through its metabolic processes, which is related to its total body mass (its volume). It loses that heat to the environment through