Originally, people thought that whales were very large fish because their bodies have a similar shape to that of fish. In 1778, Swedish biologist, Linneus, recognized that whales were not fish but mammals. They share some common characteristics of all mammals.
A humpback mother and her calf.
- They are endothermic: Their body-core temperature stays the same, it does not change with the temperature of their environment.
- They breathe air with lungs. Unlike fish, whales do not remove oxygen from the water but breathe air directly. This means a whale must come to the surface of the water at regular intervals to breathe. Whale nostrils, called blowholes, are located on top of the head. When a whale surfaces it exhales the air from its lungs. This is called blowing.
- They give birth to live
young. Mothers (called cows) suckle their young (calves),
on milk secreted by mammary glands.
- They have hair. Although they are not covered in hair or fur like many mammals, whales have some bristles, usually on their heads.
A mother bottlenose dolphin and her calf.
Perhaps, people are so intrigued by whales because they live their whole lives in the water. The only other mammals that spend their entire lives in the water are from the order Sirenia. This order includes three species of manatee and one species of dugong.