Ectotherm is a cold-blooded animal. Cold-blooded animals regulate their body temperature by using their external environment; this can includes the sun, warm water, or heated rocks. They are the opposite of endotherms, which induce internal temperature control. Most cold-blooded animals live in areas where the temperature is constant. Ectotherms include amphibians, fish, reptiles, and invertebrates. Turtles are reptiles so they are ectotherms.