Bergmann's rule

Berg·mann's rule  (bûrgmnz)

n.

The principle that in wide-ranging, warm-blooded animal species, individuals living in a cold climate tend to be larger than individuals of that same species living in a warm climate.

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[After Carl Bergmann (1814-1865), German biologist.]

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Bergmann's rule  (bûrgmnz)

The principle holding that in a warm-blooded animal species having distinct geographic populations, the body size of animals living in cold climates tends to be larger than in animals of the same species living in warm climates. Animals with larger bodies are generally more massive and thus produce more body heat. They also have smaller surface areas relative to their mass, resulting in a relatively lower rate of heat radiation. The Bergmann rule is named for the German biologist Karl Bergmann (1814-65). Compare Allen's rule.