Homeotherm

Homeotherm refers to an animal that maintains a relatively constant body temperature regardless of the temperature of its environment. The term derives from Greek roots meaning “the same heat.” Most homeotherms achieve this constancy through endothermy, producing metabolic heat and regulating heat loss to keep body temperature within a narrow range.

Classic homeotherms are the mammals and birds. They use mechanisms such as shivering and nonshivering thermogenesis, insulation from fur or feathers, and controlled blood flow to the skin. Behavioral strategies, including seeking shade or sun, nesting, and huddling, also help maintain a stable temperature.

Homeothermy is commonly contrasted with poikilothermy, in which an animal’s body temperature fluctuates with ambient conditions. Some animals exhibit regional or episodic variations in temperature (heterothermy), such as torpor or hibernation, or regional endothermy in certain aquatic species, which can blur the distinctions between categories.

Maintaining a constant body temperature is energetically costly, but it supports sustained metabolic activity, mobility, and occupation of diverse environments. The distribution of homeothermy is largely associated with mammals and birds, with some variations and exceptions in other groups.