# Mammals

Mammals have several unique characteristics that differentiate them from other types of animals. Most mammals have hair or fur covering their bodies. They are also capable of regulating their body temperature. A mammal's metabolism controls heat production, and sweat glands help cool the body, enabling the mammal to maintain a constant body temperature over a wide range of environmental temperatures. One other difference from other types of animals is that mammals give birth to fully formed babies, and female mammals produce milk to feed their young.

Most mammals walk on four legs: only humans consistently walk upright on two legs. Aquatic mammals have flippers, or fins, for swimming rather than legs. Common mammals include primates, such humans and monkeys, marsupials, rodents, whales, dolphins, and seals.