A hooded seal mother nurses her pup for only three to five days
True seals are built for the long haul at sea and are clumsy ashore, bouncing along in a motion nicknamed galumphing. Mothers fast while nursing, pouring fat-rich milk into their pups, then leave. Hooded seals wean in under a week, and the abandoned pups live off their own blubber for weeks.
Earless seals, or phocids, form the family Phocidae, one of three pinniped groups. They have simple ear holes instead of external flaps, and most live in polar, subpolar and temperate seas; the monk seals are the tropical exception, and the Baikal seal is the only one confined to fresh water. Sizes span from the ringed seal, about 1.17 metres and 45 kilograms, to the southern elephant seal, up to 5.8 metres and 4,000 kilograms, the largest of all carnivorans.
Where sea lions are agile sprinters, phocids are economical cruisers able to forage far from land. They swim by sweeping the rear body side to side, steering with the front flippers. Because those hind flippers are fused toward the pelvis and cannot turn forward, seals on land wriggle with belly muscles; the polar explorer Edward Wilson called it lolloping. Their bodies are more streamlined for water, with retractable nipples and internal genitals. When diving, air is pushed out of the lungs into upper airways where gas cannot readily enter the blood, protecting against the bends, and blood sinuses in the middle ear swell to balance pressure.
Communication differs within the family. Northern phocine seals do not bark; they slap the water and grunt, and some clap underwater, apparently in both displays and confrontations. Southern relatives are vocal: elephant seal bulls roar on beaches, and Weddell and leopard seals sing beneath the ice.
Breeding is a race against the clock. Pregnant females fatten at sea, then come ashore or onto pack ice, often hundreds of kilometres from their feeding grounds, and fast while nursing. Lactation lasts five to seven weeks in monk seals. Orphaned mothers sometimes adopt pups, while milk thieves that raid sleeping females can starve the rightful pup. Weaned pups fast for weeks or months, among the longest fasts of any mammal. The earliest known fossil, Noriphoca gaudini, comes from Italy around the Oligocene-Miocene boundary.
Source: Earless seal
