|
Life in the Southern Ocean
Factfile |
 Life in the Southern Ocean |
 |
Seals
The seal population in the Southern Ocean has recovered well following years of sealing. Six species of seal inhabit the Antarctic and four of these, the Crabeater seal, the Weddell Seal, the Ross Seal and the Leopard Seal are native to Antarctica itself, breeding on the surrounding ice. The other two, the Elephant Seal and the Fur Seal use the waters for feeding, but breed in surrounding islands like South Georgia. This part of the world, despite the cold, has such a plentiful food supply for seals that over half the world’s seals live in the Southern Ocean.
Seals are mammals. They spend most of their time in the ocean, coming to the surface to breathe, or to the ice for a rest. They must, however, return to land, or more commonly ice, to breed. Pups are usually born in late winter. Like whales, seals have very good insulation, in the form of blubber, to keep them warm in the cold environment. All seals have flippers to help them swim. Most seals use their back flippers, but Fur Seals use their front ones instead. This is because they are part of the sea lion group. Consequently they have ears as well, unlike other seals.
Crabeater seals - CMEM(M) Pete Morewood
Crabeater seal – These seals are by far the greatest in number, with a population of over 15 million. They tend to live on the pack ice either on their own or in twos or threes. The crabeater seal does not eat crabs; instead it has specially developed teeth which strain the water for krill. Despite these seals being up to 2.4 metres (8 feet) long, they are readily hunted by killer whales.
Weddell seal – The Weddell seal was named after the British Whaling Captain James Weddell. They are the most easily seen seals, as they live in groups of several hundred on the fast ice near to the water. Male Weddell seals can be up to 3.3 metres (11 feet) long and weigh around 450 kg (990lbs). They are very good divers and can remain under the water for over 1 hour. This gives them plenty of time to hunt the fish they eat. In the winter, these seals can survive below the ice, as their teeth enable them to keep air holes open in the ice for breathing.
Ross Seal – Ross seals (named after Sir James Ross) are the least common of the seals and no one knows exactly how many of them there are. The main reason for this is that they like to live further up the pack ice and therefore further away from the coast. Ross seals can be up to 3 metres (10 feet) in length. They mainly feed on squid and octopus, but also eat fish.
Leopard seals – These have very different feeding habits to the other seals. They have very complicated teeth which, as well as enabling them to strain for krill, can kill fish, penguins and young crabeater seals. In fact their diet is a mixture of these, with squid as well! Leopard seals live on the pack ice, but are quick swimmers and therefore the penguin’s greatest threat.
Southern Elephant seal
Elephant seal – The elephant seal, as the name suggests, is the largest of the seals. Males can be up to 4½ metres (15 feet) long, and weigh 4 tonnes. They breed differently to the other seals, as one male will breed with approximately 70 females. The males can be very aggressive towards other males and so nasty fights occur. Elephant seals live mainly in the water, with blubber up to 15cm (6inches) thick to keep them warm. They mainly eat squid, but also fish.
Fur seal – These were the most popular seals with the seal hunters and consequently had the lowest numbers. The population has now recovered extremely well, though. Adult fur seals are often longer than 1.8 metres (6 feet) and are the only eared seal in Antarctica. Also unlike the other seals, it has a fine hair covering that act as insulation. Fur seals mainly eat krill but supplement this with fish and squid.
|
|
|
|
|
|
|
|
|
|
