Although dolphins swim with the fish, they are classified as mammals, meaning they are vertebrates -- or organisms with a spine -- that belong to the class Mammalia. The bottlenose dolphin, with a sleek, silvery body, is probably most familiar, but the killer whale, or orca, is actually a dolphin, too. Dolphins live in schools of up to 12 members and are viewed as highly intelligent creatures.
Characteristics of All Mammals
All mammals are vertebrates and warm-blooded. Mammals give birth to live babies and nurse their young. They breathe air and have some hair on their bodies.
Like any other mammal, dolphins regulate their own body temperature and surface frequently in order to breathe air. A dolphin's blowhole acts like a nose and allows the animal to surface for air. Although they look smooth, dolphins have a small amount of hair around their blowholes. Female dolphins give birth to live young and have mammary glands for lactation.
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