ABSTRACT
Marine mammals are species that utilize the ocean environment for all or part of their life cycle. This includes whales, dolphins, porpoises, seals, sea lions, sea otters, walruses, polar bears, manatees, and dugongs. Land mammals began to live in the ocean over 50 million years ago. Remarkably, new species are still being discovered, both through direct observation and genetic analyses. Advances in research techniques continue to expand our understanding of the unique life histories of marine mammals.
