Habitat: Polar waters and tropical seas.
Geographical spread: The oceans of the world, with the principal populations in the southem hemisphere. The Blue migrates between the Arctic and Antarctic where it feeds in the summer, to subtropical waters where it breeds.
Current population: By 1965 it is estimated that there were 6,000 Blue Whales left. The total population is not known today but is believed to still be in the low thousands.
Status: The IUCN list the Blue Whale as endangered.
Size: Head to tail length 27m. The Blue Whale is the largest animal ever to have lived on earth.
Weight: 150 tonnes.
Average life expectancy: 80 years.
Normal diet: Feeds predominately on krill, a small shrimp-like crustacean which occurs in huge numbers in polar waters. Like all Baleen whales, the Blue whale has baleen plates, through which krill is strained. The baleen plates are fringed with b ristles and the organisms are dislodged from the baleen by the tongue.
Normal lifestyle: Blue whales are migratory and travel 1000s of kilometres between their summer and winter grounds. Blue whales mate in the warm waters of the tropics and then migrate to the polar feeding grounds where they feed for 3-4 months on the rich supply of food. They then migrate back to the tropics segregated by sex and age, the older and pregnant whales migrating first, with the sexually immature whales bringing up the rear. As this migration takes the Blue whale away from its feeding ground, they eat virtually nothing for at least 4 months and live on body reserves. Females give birth in warm tropical waters because the young only have a thin layer of blubber to keep them warm. Females give birth to a single calf about 23m (7ft) long and weighing 2 tonnes. The calves are suckled for 5-7 months and follow their mothers on the spring migration towards the polar seas. Once weaned the calves feed on krill and follow the nommal cycle of migrations independently.
Previous geographical spread: Not relevant.
Reasons for decline: As soon as man developed a device (the harpoon gun, 1864) capable of killing such a huge animal, Blue whales have been exploited. The whaling industry took off in leaps and bounds, Blue whales were hunted and stocks exhausted in the northem hemisphere, so whalers moved on to the southem hemisphere populations. In the summer season of 1930/31 29,000 Blue whales were killed. Whales are wanted for their oil which is used in edible foodstuffs among other things and the Blue whale was particularly attractive to whalers because of its huge size. Scientists began to warn about the danger of killing in such huge numbers but whaling nations paid no attention and soon Blue whale numbers were reduced from 200,000 to a thirtieth of thei r original abundance. In the peak years of Antarctic whaling between 1927 and 1936, Blue whales formed 80% of the catch. When Blue whales were given total protection from hunting in the southern hemisphere in 1965, there were about 6,000 left. The Intern ational Whaling Commission (IWC) was formed in 1946 and the International Whaling Convention adopted, with the aim of regulating whale catches and conserving whales. Hunting however was not banned until the Blue whale was on the point of extinction. Japa n remains the principal whaling country and the main market for whale meat.
Current threats: Decreases in Blue whale numbers led to an increase in other krill eating predators such as Crab-eating seals, Antarctic fur seals, Penguins and other seabirds, these are bound to provide unwanted competition for an already deplete d Blue whale stock.
Conservation projects: The Indian Ocean north of 55 S became a designated whale sanctuary in which all commercial whaling is banned in 1982. This was not formally accepted until 1992. In 1992 France proposed the same status for the entire Southern Ocean south of 40 S. These two huge sanctuaries should protect the Blue whale throughout its annual cycle, by covering both their breeding and feeding grounds.
Special effects: There are 2 subspecies; the Blue whale fB. m. musculus) and the Pygmy blue whale (B. m. brevicauda). The Pygmy blue whale is 24m long, weighs 70 tonnes and lives for 65 years. It is found in the S Indian Ocean and the S Pacific.
File last modified Thursday, October 3, 1996