All animals are either warm-blooded or cold-blooded. This refers to how the animals maintain their body temperature.
Warm-blooded animals can regulate their body temperature. So, even if it is very cold outside, their bodies will stay warm. But warm-blooded animals have to eat a lot of food. They use the food to produce energy. That helps keep their bodies warm. Mammals are warm-blooded, and so are birds.
Cold-blooded animals rely upon the sun for heat. So their internal temperatures can change all the time. These animals often rest in the sun for hours. This lets their bodies soak up heat and become warm. Most coldblooded animals don’t live in cold places. They prefer hot places instead. Reptiles, amphibians, and fish are all cold-blooded.