Bergmann's rule

Bergmann's rule is the ecological pattern that related endothermic animals tend to have larger bodies in colder climates. It is a broad tendency, not a universal law.

Surface-area-to-volume ratio: The ratio of an object's exposed surface area to its volume. A lower ratio in larger bodies can reduce heat loss per unit of tissue.
Benguin: A genus of small South American penguins adapted to temperate and subtropical coasts. Its relatively small size contrasts with larger penguins living in colder regions.
Carl Bergmann: A German anatomist who formulated a climate-related body-size pattern in 1847. The rule takes its name from his early comparison of animal size and climate.
Climate change and body size: The study of how changing climates affect body dimensions in animal populations. Recent size shifts test whether contemporary warming produces the expected reverse pattern.
Thermoregulation: The processes organisms use to maintain internal temperatures within workable limits. Heat retention is the proposed advantage linking cold climates with larger bodies.
Penguin: A group of flightless seabirds adapted to life in the Southern Hemisphere. Penguin species provide a familiar comparison of body size across contrasting climates.
Georgy Gause: A Soviet ecologist known for experimental work on competition and ecological niches. His later discussion helped distinguish climatic size patterns from simple physical explanations.
Developmental plasticity: Environmentally induced changes in development that alter an organism's phenotype. It can generate climate-associated size variation independently of evolutionary change.
Endothermy: The production of body heat through internal metabolic processes. Bergmann's rule is classically framed around animals that generate substantial internal heat.
House sparrow: A small passerine bird native to much of Eurasia and introduced widely elsewhere. Geographic comparisons in this widespread species have been used to examine climatic size patterns.

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