| Bergmann's Rule |
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allows it to radiate less heat in a cold climate.]] In Zoology , Bergmann's Rule is a principle that correlates environmental temperature with body mass in Warm-blooded animals. It asserts that within a species, the body mass increases with Latitude and colder Climate . Among Mammal s and Bird s, individuals ''of a particular species'' in colder areas tend to have greater body mass than individuals in warmer areas. For instance, White-tailed Deer are larger in Canada than in the Florida Keys . The rule is named after a nineteenth-century German biologist, Christian Bergmann . Bergmann's rule and Allen's Rule are examples of Cline s frequently seen in Mammal s. This rule operates as larger animals have a lower surface area to volume ratio than smaller animals, so they radiate less body heat per unit of mass, and stay warmer in cold Climate s. On the other hand, warmer climates impose the opposite problem: body heat generated by metabolism needs to be dissipated quickly rather than stored within. Thus, the higher surface area-to-weight ratio of smaller animals in hot and dry climates facilitates heat loss through the skin and helps cooling of the body. However, some notable exceptions of species with large mass and small surface-to-volume ratios that reside in warm climates exist, such as the African elephant. In this case, similar thermoregulatory optimizations may be operating, such as mass homeothermy to resist a significant ''rise'' in core body temperature in warm climates. Anecdotally, elephants are more frequently found in the shelter of shade when they are accompanied by calves, which have a significantly higher surface-to-volume ratio, and are much more prone to changes in temperature from radiant sources in the environment. (''For similar arguments with references, see {Link without Title} ''). For , Human Weight . SEE ALSO REFERENCES
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