Marine Mammals: Lesson for Kids

Instructor: Jenny Homer

Jenny has masters' degrees in public health and public administration.

Would you be surprised to learn that in some ways a group of ocean animals have more in common with humans than they do with fish? These animals are called marine mammals, and we'll learn about them in the following lesson.

What Are Marine Mammals?

When we think of ocean animals, we tend to think of fish. But fish are not the only kind of creatures who call the sea their home. One fascinating group are marine mammals. They are different from fish and share many traits with mammals that live on land. Even so, their bodies are not the same as land animals. Marine mammals are able to spend long periods of time in the water. Some cannot live on land at all, some come out on land once in a while, and others get all their food from the ocean.

In this lesson, we'll first cover the characteristics that land and marine mammals share. Next, we'll discuss five groups of marine mammals.

Characteristics of All Mammals

Mammals can be very small or huge, but they all have certain things in common:

  • Warm-blooded - Their body temperature is at a certain level no matter what the weather is outside. Warm-blooded mammals usually keep their body temperature from about 97 to 104 degrees Fahrenheit.
  • Breathe air through lungs
  • Vertebrates - They have a backbone.
  • Have babies who are born live (not hatched from an egg)
  • Have hair on their body at some point during their lives (even if before they are born)
  • Mothers nurse their babies with milk made in a part of the body called mammary glands. This is why they are called mammals.

Can you think of an animal that's a mammal? People are mammals, as well as dogs, cats, and cows.

Marine mammals have some amazing features that allow them to spend long periods of time in the water. The shape of their bodies makes them better swimmers. Many marine mammals have a layer of fat under their skin called blubber that keeps them warm in the water.

Because all marine mammals need air, they must swim to the surface of the ocean to breathe. That's why you might see a dolphin or whale at the surface of the water; they're coming up for air. When under water, they need air less often and can dive much deeper than land mammals because of how blood and air move through their bodies. They do not need as much freshwater as land mammals.

Five Groups of Marine Mammals

Marine mammals are usually divided into five groups.

  • Dolphins, porpoises, and whales must stay in the water. The blue whale is the largest animal in the world.


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