Endothermic Animals

Endothermic animals are commonly referred to as "warm-blooded"

California Sea Lion (Zalophus californianus) Picture
Example of An Endotherm: California Sea Lion (Zalophus californianus) near Channel Islands, California. © Blue Ocean Society

Endothermic animals are those that must generate their own heat to maintain their body temperature. These animals are commonly referred to as "warm-blooded." The term endotherm comes from the Greek endon, meaning within, and thermos, which means heat. An animal that is endothermic is categorized as an endotherm, which primarily includes birds and mammals. 

Endothermic Heating and Cooling

Endotherms generate a majority of their heat in their internal organs.

For example, humans generate about two-thirds of their heat in their thorax and about fifteen percent is generated by the brain. Endotherms have a higher metabolism than ectotherms, which causes them to consume more fats and sugars to create heat. In order to cool down, endotherms may pant causing the water to evaporate and provide cooling. Humans and other short-haired mammals also sweat. 

When endotherms are cold, they shiver which creates warmth by expending energy through its skeletal muscles. Shivering is unique to warm-blooded animals. 

Some endotherms that live in cold climates, like polar bears, have a complex set of arteries and veins that are close to each other in order for the arteries that carries the blood from the heart to warm the veins that are returning blood to the heart.

Endotherms Versus Ectotherms

The opposite of an endotherm is an ectotherm or "cold-blooded" animal.