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Are Whales Fish?

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Humpback Whale underwater portrait
Kate Westaway/Stone/Getty Images
Question: Are Whales Fish?
Whales live in the ocean, can stay underwater for long periods of time and have strong tails to propel themselves. So do fish. So, are whales fish?
Answer: The short answer: whales are not fish. Whales are mammals, just like you and me. All mammals are endothermic (commonly called warm-blooded), give birth to live young and nurse their young, breathe oxygen from air, and have hair (yes, even whales do!).

What Distinguishes Whales From Fish?

If you're still not convinced, here are some specific ways that whales differ from fish.
  • Swimming: Whales move their tails up-and-down, while fish move theirs from side-to-side (this causes the fish's whole body to undulate).
  • Breathing: Whales breathe through their blowholes, which are basically nostrils on the top of their heads. Fish take in oxygen from the water through their gills.
  • Birthing: Whales give birth to live young. Fish lay eggs.
  • Skin: Whales have smooth skin, while fish have scales.
  • Body heat: Whales are warm-blooded (endothermic), while fish are cold-blooded (ectothermic).

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