Question: are most animals endotherms or ectotherms?
Answer: Endotherms and ectotherms People, polar bears, penguins, and prairie dogs, like most other birds and mammals, are endotherms. Iguanas and rattlesnakes, like most other reptiles—along with most fishes, amphibians, and invertebrates—are ectotherms. Endotherms generate most of the heat they need internally.