Are Penguins Mammals?

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Written by Krishna Maxwell

Updated: September 20, 2022

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Penguins, or Sphenisciformes, are not mammals, but birds. They are different from mammals in that they have feathers instead of hair or fur, and unlike most mammals penguins lay eggs instead of giving live birth. Like all modern birds, penguins don’t have teeth, though most mammals do. They also don’t feed their babies with milk exactly the way mammals do, but more about that later.

Penguins are, like other birds, a type of therapod dinosaur that survived the extinction of other dinosaurs such as Tyrannosaurus Rex. Birds are much younger than mammals as a Class, having appeared on earth around 60 to 70 million years ago compared to mammals’ appearance 210 to 300 million years ago.

Unlike mammals, penguins lay eggs rather than giving live birth.

Why Do People Think Penguins Are Mammals?

People might mistake penguins for mammals because they really don’t look like any other type of bird. Auks look somewhat like them, but auks can fly. Sphenisciformes are bipedal, and they have given up the power of flight. Their wings have developed into flippers that help them swim, which they do as gracefully as other birds fly. They are warm-blooded, and smooth, dense plumage sometimes looks more like sleek fur than feathers. Their chicks often look like they’re wearing dust-colored fur coats, but they are covered with down. The black and white coloration of their plumage may also make people think of a mammal such as a honey badger, a skunk, or even a killer whale.

Emperor penguin fathers do feed their chicks with crop milk when they’re first hatched. This is a substance that resembles cottage cheese and is made of proteins and fats. It’s not regurgitated fish but a nutrient the bird actually produces from a gland in its throat. This still doesn’t make a penguin a mammal.

Only three bird species are known to produce crop milk, and they are the male emperor penguin, the pigeon, and the flamingo. Second, only the father emperor penguin produces it. Mammalian milk is produced exclusively by the mother’s mammary glands.

Another thing that might make people think Sphenisciformes are mammals is that they take great care of their young. Emperor penguins are famous for the extremity of their devotion. The male stands around in subzero temperatures for weeks incubating the egg then keeping the chick from freezing in his brood pouch. He does this until the mother returns from the sea, where she has been feeding. He then surrenders the chick to the mother and goes to the sea himself to feed, as he has not eaten the whole time and is half-starved. He no longer produces crop milk, but he and the mother take turns feeding the chick regurgitated fish and krill. They do this for five months.

Penguins, like many birds, are devoted parents who work together to raise their young. We humans tend to think of this as a human trait, but many species of birds share this behavior. Like humans, the babies of birds are very helpless and require extensive care until they grow enough to survive on their own. Penguins often live in very harsh climates so good parenting is a must if the babies are to survive.

Up Next…

  • Penguin Lifespan: How Long Do Penguins Live? Want to learn more about these odd but charming birds? Look here to learn about their lifespan.
  • 10 Incredible African Penguin Facts We usually think of penguins living on slabs of ice and fending off Killer Whales. Did you know there are hot-weather penguins that live in Africa? Check them out here.
  • King Penguin vs Emperor Penguin: What Are the Differences? What makes up penguin royalty? Find out what makes the difference between a king and an emperor here.


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About the Author

Krishna Maxwell

Krishna is a lifelong animal owner and advocate. She owns and operates a small farm in upstate New York which she shares with three dogs, four donkeys, one mule, and a cat. She holds a Bachelors in Agricultural Technology and has extensive experience in animal health and welfare. When not working with her own animals and tending her farm, Krishna is helping other animal owners with behavior or management issues and teaching neighboring farmers about Regenerative Agriculture practices.

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