Marine mammals are divided into 5 groups: pinnipeds (seals, sea lions, walruses), cetaceans (whales, dolphins, porpoises), sirenians (dugongs, manatees) and some members of the mustelid (sea otters) and ursid (polar bear) families. They have the same characteristics as all other mammals but also anatomical and physiological peculiarities that allow them to live wholly or partly in the water. Most have a thick layer of fat to insulate them against cold sea-water and can go without breathing for several minutes, direct their blood flow solely towards their vital organs (heart and lungs) and slow their heart rate so as to use less oxygen.

Californian Sea Lion (Canada, USA and Mexico)

Wild sea lions consume 7–18kg of food a day. During the breeding season, males fast for several days because they are unable to leave land to go and feed at sea if they want to continue to defend their territories and their mates. In the zoo, sea lions eat part of their food during their show and the rest at the end of it. Their keepers hand out 2–12kg of herrings, mackerels and sprats every day. Quantities depend on the season but also on individuals.

Asian Small-clawed Otter (Asia)

Asian Small-clawed Otters belong to the Mustelidae family. They don’t live in the sea but in rivers and lakes. Several morphological adaptations allow them to move efficiently in water: slender, streamlined bodies, long tails and partly webbed feet. The Asian Otter eats mainly crabs and crustaceans that it manages to extract from narrow cracks thanks to its nimble fingers.