Whales are the largest animals in world, specially blue whale with his length up to 30m and a weight up to 180 tonnes. But there are many species of baleen whales found in Antarctic waters like the fin, humpback, sei, minke, and the right whale. There are also six species of toothed whales: Sperm, Killer, bottlenose, fourtooth whale and Dolphins.
Baleen of a whale
There are two different ways Baleen whales feed. The first, called swallow feeding, they engulf a mouthful of food and water and then squeeze the water our by contracting the grooves in their throat and raising their massive tongues firmly against the roofs of their mouth. The second ways, only practised by the right and sei whale, they’re used to swim with their heads partly out of the water through a swarm of krill. They have their mouths half-open and skim food from the ocean.
The Baleen whales breed in tropical water in the north. After three months of rich feeding in the south, they migrate back to the temperate waters to give a birth to a single calf, a year after mating. The calves accompany their mothers on the next migration south, living on their mother’s milk. Six month after birth, they are able to feed themselves. Only the calves of the humpbacks and the southern right whales are dependent on their mothers for up to a year.
Balaenoptera borealis grow up to 18.5m in length and weigh up to 29 tonnes. They’re closely related to blue and fin whales, but they’re smaller and more slender. Fin whales are oceanic and make long north-south migrations although they only go as far south as 55°S. They have a lifespan of 70 years and it is thought that they may be monogamous. They were hunted after the other whales were protected, but since 1978 they have been also protected in most parts of the Antarctic.
Southern right whale
Southern right whale
Toothed Whales and dolphins
Most toothed whales are much smaller than baleen whales, only the sperm whale matches them in size. There is a great difference between the feeding habits of the toothed and baleen whales. The toothed whales mostly have quite long jaws, often armed with a row of peg-like or cutting teeth. These teeth are well adapted for seizing or cutting up quite large and active prey, and these species feed mainly on fish and squid. The size of its prey varies with the size of the cetacean.
Toothed whales differ from other mammals in having only one nostril, although two nasal passages are present.
Oscines Orca, also called killer whale, reach a length of 9m, while females reach only 8m. The average weight is 7 to 8 tonnes. Killer whales are found in all oceans, from the tropics to the edge of the polar ice. In Antarctic waters orca whale feed on penguins and seals. They eat also fish, but they prefer warm-blooded prey. Packs of killer whales have been seen to attack fin and other whales larger than themselves, tearing mouthfuls of flesh from their living bodies. They are strong enough to toss a fully grown adult sea-lion up into the air. Orca whales live mainly in small packs, which occasionally merge into large herds. The Antarctic population is estimated at about 200 000. In the Antarctic, whalers have shown little interest in killer whales, although about 900 were taken by Russian ships in 1978.
Southern bottlenose Whale
Southern bottlenose whale
The blunt head of the sperm whale, which makes up one third of its body length, contains a wax-filled "case" on top of its skull. The whale can change the density of this spermaceti wax as it dives, thus altering the whole buoyancy of its body.
They hunt at great depths many species of squid. They reach a speed of 7 to 8 km per hour to depths of 1’000m and below, where they can stay for 45 minutes. In these pitch-black waters they use sonar to locate their luminous prey.
The sperm whales are well organised. Schools of females and young males live in temperate waters all year and are joined by the males during the summer when mating takes place. Each male has a harem of 20 to 30 females. The calves are born after a gestation period of 15 months and are then suckled for one to two years. But during feeding sperm whales are solitary animals.
At the end of the 18th and the first half of the 19th century, large herds of sperm whales were hunted in southern waters. After that the demand on whale oil decreased and the whale fishery collapsed. Interest revived in the 1950s and about 5’000 animals a year were caught from 1950 to 67. Declining numbers stopped hunting in 1979.
Southern fourtooth whale
Berardius arnuxii has an average length of 11m and weight of 8 tonnes. The beaked whales are generally smaller than the bottlenose whales, with a less pronounced forehead. They form large groups, but they’re still difficult to apart them form the bottlenose. Very little is known about them.
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