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Marine Mammals
 Marine Mammals

Mammals are probably the most familiar group to you — because humans are mammals! We mammals have a few things in common.

Below, you will see some of the marine mammals that Signals of Spring - ACES scientists are tracking. All marine mammals are protected by the Marine Mammal Protection Act of 1972.

The major groups of marine mammals are:

All mammals:

  • give birth to live young. Baby mammals develop inside the mother.
  • nurse their young. Mother mammals produce milk.
  • are endothermic, sometimes called "warm blooded." This means that they can maintain their body temperature separately from their environment. Mammals keep themselves warm, unlike a lizard, for example, that must bask in the Sun to get a warm body temperature.
  • have hair, which can either be full like a polar bear or just a few hairs on the chin like a dolphin.

Cetaceans (Suh-TAY-shuns): Whales, Dolphins, and Porpoises

two photos of whale blowholes

These marine mammals have sleek, bullet-shaped bodies, and a strong tail that propels them to swim. Most have a long 'nose' area, or rostrum, and a dorsal fin on their back. Cetaceans move their tails up and down to push themselves through the water. Fish, in contrast, move their tails from side to side.

Cetaceans must breathe voluntarily — unlike humans who breathe without thinking about it. To breathe, cetaceans come up to the ocean's surface and breathe through a special hole on the top of their head called a blowhole.

photo of two dolphins swimming

Unlike most mammals, cetaceans do not have much hair. Instead they have layers of fat under their skin called blubber. This blubber keeps the animals warm, helping them regulate their body temperatures.

There are two major groups of cetaceans. The first is the toothed whales. They include the dolphins and porpoises, and as well as the beluga, orca, and sperm, and other whales. Most toothed whales eat fish or squid and use their teeth to rip apart their prey.

photo of a Brydes Whale

Cetaceans in the second major group have large 'toothbrush-like' plates in their mouths called baleen and are known as the "baleen whales." The baleen allows these animals to strain their food out of the water. Their diet tends to include smaller prey such as krill, a shrimp-like animal.


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Pinnipeds: Seals, Sea Lions, and Walruses

two photos of Harbor Seals

Pinnipeds are interesting marine mammals because they must come on land to give birth to and nurse their young. While they use both land and sea habitats, they are much more agile in the water. Pinnipeds have front and hind flippers. They use their long front flippers to propel themselves and steer through the water.

There are three main groups of pinnipeds: true seals, eared seals, and walruses.

photo of Seals

True seals move on land by flopping around on their bellies.

Eared seals, a group which includes the fur seals and the sea lions, have an ear flap on the outside of their bodies. They can also use their longer flippers to walk on land.

photo of a Walrus

Walruses are distinguished by their long tusks. They use these tusks to help dig up shellfish from the sea floor.


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Polar Bears

Most members of the bear family are land dwellers, but polar bears spend most of their lives at sea. The habitat of these carnivores includes land, sea and most importantly, ice.

Polar bears have coarse, hollow fur that traps heat close to their bodies, helping them to survive in their cold Arctic environment. Their white color camouflages them as they stalk their favorite prey — seals.

Polar Bears:

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