What is a whale?

Whale tail
Australia is working to stop the resumption of commercial whaling (Photo: Dave and Fiona Harvey)

Whales belong to a wonderfully diverse group of the most aquatically specialised of the world's mammals called Cetaceans.

These animals range is size from porpoises that are a little over a metre long, right through to the largest animal that lives on earth, the magnificent blue whale which can grow up to 24 metres and can weigh 84 tonnes.

Whales have undergone such extraordinary evolutionary changes in adapting to life in the oceans that it is hard to see what their ancestors might have been. By tracing through the fossil record we can now see that whales have evolved from much smaller land-based mammals that entered the water over 50 million years ago.

The general term 'whale' usually refers to the 'great whales' which includes the largest of the toothed whales, the sperm whale of Moby Dick fame, and all of the large baleen whales that were once hunted almost to extinction.

Cetaceans are divided into two broad groups; those with teeth, the toothed whales, and the filter feeders that catch small prey with special sieves in their mouths called baleen, the baleen whales.

Toothed whales

Four species of toothed whales are found in Antarctica. Except for the sperm whale, they are much smaller than the baleen whales and weren't widely hunted. The other species are the southern bottlenose whale, the orca (killer) whale and the southern fourtooth whale. They all have teeth which enables them to feed on larger prey such as fish and squid. Killer whales also eat penguins and seals, typically hunting in packs.

Baleen whales

Six species of baleen whales are found in Antarctica, including the huge blue whale. Other baleen species are the fin, southern right whale, sei, minke and humpback. The name baleen refers to a hug, hairy plate in the whale's mouth, which acts as a sieve. This plate enables these whales to sieve or filter krill, plankton and crustaceans out of sea water.

Whale migration

Many Southern Ocean whales are migratory, heading to tropical waters during the Antarctic winter. Calves are born in these warmer waters, as the new born young would not survive in cold seas. The whales return south in the austral spring, following the receding ice edge; an area of high biological productivity, which provides a rich feeding ground. A young calf will accompany its mother for several years on the annual migration and females will not mate again until their calf is independent.

Whale exploitation to protection

The devastating exploitation of whales for the richness provided by their oils and other products led to much of the exploration of the globe by sea-faring nations.

Over 1.3 million whales have been taken from Antarctic waters this century. Although greatly reduced in numbers, six species of whales still live in Antarctic waters. It is estimated that there were over 225 000 blue whales before their exploitation; today there are less than 2000.

The whale then became the icon of the modern conservation movement as the plight of these animals was recognised. We now recognise and value the role these creatures play in healthy marine ecosystems and millions of people now have the memorable opportunity to see a whale 'up close and personal' as part of the new whaling industry; whale watching.

This page was last modified on 26 April 2012.