Marine mammals

Sirenians, the manatees and dugongs, are slow plant feeders found in warm, shallow coastal habitats. Pinnipeds, the seals, sea lions and walruses, bear young on land, but spend most of their time in the ocean. Cetaceans, the dolphins, porpoises and whales that spend all of their lives in the ocean, include both toothed species that are carnivorous predators, and filter-feeding baleen whales that consume huge quantities of tiny plankton. In size, marine mammals range from small seals and porpoises to the largest animal that has ever lived, the blue whale. Many cetaceans and pinnipeds dive to remarkable depths to feed, feats only recently discovered using digital tags that record the animals' movements, direction, and depth over time.

Marine mammals play important ecological roles as both predator (many hunt for fish) and as prey, both for sharks and other, larger marine mammals. Humans have also long hunted marine mammals for food and fur. Although hunting pressures have declined, marine mammals still suffer from low numbers and inadvertent human activities such as certain fishing methods, boating and shipping traffic, and increasing ocean noise.