-  behaviour
 -  species
 -  whales, not fish

Whales, the largest animals on earth, belong to a family of mammals known as cetaceans. Unlike fish, whales are warm-blooded, breathe air and give birth to live young. Scientists believe that they evolved from land mammals with four legs, though they are now supremely adapted to underwater life. They have excellent hearing and are two to three times more efficient than land mammals at using oxygen in inhaled air. Whales have collapsible ribcages which assist them with deep diving, and they have layers of insulating fat, called blubber, to protect them from the cold.

Humpback whale. © Newman/Greenpeace

Whales are difficult creatures to study because they are long-lived, reproduce slowly and most are highly migratory. Pacific Gray whales, for example, migrate from Alaska to Mexico every year, traveling about 20,000 kilometres annually. Most whales live to approximately 40 years of age, though others, such as the Fin, can live to be 90. Bowhead whales may be especially long-lived. In 1993, a large male killed by the Alaskan Inuit was found to have been carrying in its flesh a stone harpoon point. Since this kind of harpoon is not known to have been in use after 1900, it suggests that some individual Bowhead whales may live up to 100 years of age.

Since it is very difficult to count whales accurately and population changes occur very slowly, it is impossible to tell if a population is growing or shrinking in the course of a few years' study. In fact, the size of some populations of whales is known no more accurately than plus or minus 50 percent.

What is known, however, is that whales can be found in all oceans of the world, and under the right circumstances, they can be seen from almost any coastal country. Whale watching has become a popular pastime in more than 87 countries,- the unique behaviours and characteristics exhibited by whales make them fascinating to observe in the wild.

Quick facts about whales:

There are two main types of whales: toothed whales and baleen whales. Toothed whales include the Sperm whale and many small species such as the Narwhal and Beluga. The others are baleen whales, which have hundreds of comb-like plates made up of stiff hairs instead of teeth. These form a sieve that filters food out of the seawater. Most large whales feed predominantly on tiny shrimp-like creatures such as krill. The Blue whale, is the largest animal to have ever lived on the earth, and is typically 25 metres long.

Baleen detail of a Gray whale underwater. © Nolan/Innerspace Visions

• Whales have mammary glands with which they feed their young. A Southern Right whale calf can drink up to 200 litres of milk every day.
• Whales, like humans, have a four-chambered heart.