What Are Marine Mammals?

Steller sea lions Photo courtesy Sue Keller.

Mammals are animals that breathe air through lungs, are warm-blooded, have hair (at some time during life), bear young alive, and suckle their young.

Marine mammals are a diverse group thought to have evolved from terrestrial ancestors to aquatic life through a number of unique physical adaptations. Representatives are found in every ocean, on every continent, and in a variety of ecological roles, including herbivores (manatees), filter feeders (baleen whales), and apex predators (killer whales).

In this website we present information on three groups of Alaska marine mammals: cetaceans (whales, dolphins, and porpoises), pinnipeds (seals, sea lions, and walrus), and marine fissipeds (sea otter and polar bear).

Cetaceans and pinnipeds exhibit extraordinary anatomical and physiological adaptations to a marine existence. Consider the physical demands on a warm-blooded, air-breathing animal living an amphibious or totally marine existence. Marine mammals have adapted to the extreme temperatures, depths, pressure, darkness, and density of the medium they live in.