Marine mammal Marine mammal Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They do not represent a distinct taxon or systematic grouping, but rather have a polyphyletic relation due to convergent evolution, as in they do not have an immediate common ancestor. They are also unified by their reliance on the marine environment for feeding. Marine mammal adaptation to an aquatic lifestyle varies considerably between species. Both cetaceans and sirenians are fully aquatic and therefore are obligate water dwellers. Seals
The Marine Mammal Center no longer capable of fending for itself. Some animals may have suffered injuries that have left them blind or otherwise disabled. Although their health is stable, they may no longer be able to survive independently in the wild. These too, are considered unreleasable. In these circumstances, the Marine Mammal Center works with the National Oceanic and Atmospheric Administration (NOAA) and the National Marine Fisheries Service (NMFS) to find a permanent home for the animal in an approved zoo or aquarium. In May, 2011, the San Francisco Zoo accepted two such animals, both are male California sea lions; named Silent Knight