Seals

Elephant and leopard seal
          Seals are well adapted to cold Antarctic waters. Some have layer of dense fur and others a layer of blubber beneath the skin, which is equally effective in the air or under water. Seals are divided into two main types: The true of "earless" seals, which evolved from otter-like ancestors. The otariids is the other type, which includes fur seals and sealions. They have visible earflaps, and use all their limbs for locomotion on land , which they do very well

Elephant and leopard seal
          Leptonychotes weddelli commonly weight up to 400kg and measure 3m. With their living on or under the fast-ice near the Antarctic coast all year round, they are the most southerly occurring mammal in the world.

          They feed mainly on fish, squid and crustaceans. Their large eyes are well adapted to the low light on dives to depths to 600m or more. Like whales and dolphins, they use sonar to locate their food and to find their way back to holes in the ice. The weddell seals spend much of the winter underwater, breathing at holes in ice which keeps open with its teeth. For this reason they live only up to 18 years, the teethes become worn down.

          During September and November, groups of half a dozen pregnant females and one male gather on broken ice to give birth. The pups weight 25kg at birth, double their weight in then days, and start swimming within a month. They reach sexual maturity at three years

Ross seal
          Ommatophoca rossii is the smallest with a length of 2.3m and weight up to 200kg. They have a dark uniform which is grey along the back and the flanks and silver grey to white underneath. They also have large eyes and a small head. Their long rear flipper makes up more than 20 per cent of their body length.

          Very less is know about Ross seal, because they are living in the thickest areas of the pack-ice. They live singly or in small, widely scattered groups and feed of squid, fish and krill.

Crabeater seal
          Lobodon carcinophagus grow up to 2.7m long and have a weight of over 250kg. With a world population estimated at 40 million, this seal is one of the world’s most abundant large mammals. Crabeater seals are now the single biggest consumers of krill, accounting for 63 million tonnes a year. This is more than all the remaining baleen whales put together. Their numbers have increased enormously in the last 50 years as whales were hunted almost to extinction. For whales to make a comeback the crabeater population may have to fall, but it is not clear how this could happen.

          The crabeaters have remarkable five-pointed teeth, the upper and lower rows of which interlock to form a strainer, so they can retain the krill while allowing water to be expelled. They are mostly dark grey, but in summer the coat can bleach almost to white.

          Because crabeaters seals inhabit the pack ice little is known about their behaviour. Pups are maybe born on the pack-ice in the spring. The mother suckles the pup for four weeks, during which it grows rapidly from 20 to 113kg in weight. During this period, the male rigorously defends an area of 50m around them, and there are frequent competitive fights with other males. Even the females are aggressive during this time. There is some evidence that they may be monogamous, although this is rare in seals.

Leopard seal
          Hydrurga leptonyx is 3m long and weight about 350kg, the females are usually larger. they are build for speed to hunt penguins, fish, squid or young crabeater seals. But they also eat Krill with similar teeth than crabeaters. Leopards have a massive lower jaw to trash the penguins against the water before eating.

          Little is known about their reproductive behaviours except that they feed from the pack-ice in mid-summer, and the young take part in their annual northward migration.

Southern Elephant seal          Mirounga leonina are the largest seals which breed on the all the Subantarctic islands. Adults males are 6-7m long and weight up to four tonnes. Females are seldom more than 3.5m long and may weight 1 tonne. The males fight for control of harems of up to 50 females when they haul out on the beaches in September to give birth to their pups.

          The females fast for 30 days while suckling their pups. By then the pup is big enough to fend for itself at sea but its mother will normally have lost about 200kg in weight. The dominant "beachmaster" males may spend 90 days ashore without food, defending their territories sometimes to death and breeding with as many females as possible. After a few months at sea to regain condition, both males and females return to their beaches in March to moult.

          Their size may be related to their feeding habits. Elephant seals take large fish and squid, and probably they have to dive deep for them. The bigger the seal, the greater the economies in diving and hunting at depth.

Antarctic fur seal          Arctocephalus gazella is very nimble on land, compared with other Antarctic species. They can run and walk, even over quite steep ground. Males are 2m long and weight over 100kg. They are stoutly built, with a heavy neck and shoulders. The females are only 1.5m long, maneless and weight less than 50kg.

          Antarctic fur seals breed in the late spring and early summer south of the Antarctic Convergence. Males have harem of 4-5 females. The females remain with their pups four eight day, suckling at six-hourly intervals. Then they have to go back to the sea to feed on a diet of fish or crustaceans to synthesise more milk. During these three to six days the pups find sheltered corners to hide. They greeting their mothers noisy with dog-like barking and whimpering on return. The pups which weight 5.9kg at birth take much longer to wean up, about 115 days.

          During this period the males spend most of their time defending their territorialboundaries, losing weight at the rate of 2 kg per day. If they fight. the males slash at each other with their sharp canines with which they capable of inflicting severe wounds. At the end of April they disappear to the open sea until the next breeding season.

Phytoplankton, krill, fish

Whales