what are mammals
Mammals are the only animals that can produce milk. age fotostock/SuperStock. A mammal is an animal that breathes air, has a backbone, and grows hair at some point during its life. In addition, all female mammals have glands that can produce milk. Mammals are among the most intelligent of all living creatures. Mammals include a wide variety of animals, from cats to humans to whales. There are about 5,000 species, or kinds, of living mammal.