Mammals nurse their young, have four limbs, are helpless at birth, have large brains and have hair all over.

They are warm-blooded vertebrates and live in habitats all over the world. Most mammals live on land, but some, like whales, live in water.

Like birds, mammals eat every kind of living thing.

Mammals come in different sizes. The largest are blue whales, which can be over 100 feet

long. The smallest are bats, which can be smaller than 2 inches!