They share five characteristics with other mammals. Mammals are warm-blooded. That is, they maintain a high and constant body temperature independent of the surroundings. Mammals give live birth. Baby whales, called calves, are born in the water.
Mammals nurse their young.
A mother whale's milk is rich in fat, so the calves develop a thick layer of blubber. Mammals breathe air. Whales breathe air through nostrils called a blowhole, located on top of the whale's head. When it needs oxygen, a whale surfaces, thrusts its blowhole clear of the water, exhales, and takes a deep breath of air into its lungs. Mammals have hair.