Are whales fish?
No, whales are not fish. They are mammals: they breathe air through lungs, are warm-blooded, give birth to live young and feed their babies milk.
Fish breathe with gills, are usually cold-blooded and mostly lay eggs. Whales breathe air through blowholes on top of their heads and must surface regularly. Their tails move up and down when swimming, while fish tails usually move side to side.
Whales evolved from land mammals about 50 million years ago. Their closest living relatives are hippopotamuses. Fossils show early whale ancestors with legs that gradually adapted to life in water.
Other marine mammals
Dolphins and porpoises are small toothed whales. Seals, sea lions, walruses, manatees and sea otters are also marine mammals. Like whales, they breathe air and nurse their young, even though they spend much of their lives in water.
Whales are divided into two main groups. Baleen whales, such as blue and humpback whales, filter tiny food through plates in their mouths, while toothed whales, such as sperm whales, orcas and dolphins, hunt fish and squid.
Did You Know?
Whale calves are born tail first, which helps prevent drowning during birth. Their mothers or other whales often push them to the surface for their first breath.