The Blue whale

The Blue whale is, and always has been, the largest animal ever to exist on earth. This whale can grow to a length of 33m (110ft) and weigh 190 tonnes but on the average it is much smaller. The Blue whale is called a "rorqual" a Norwegian word for "furrow" and refers to the pleated grooves running from its chin to its navel. The throat grooves, in addition to streamlining the shape of the whale, allow the throat area (cavum vent-rale) to expand tremendously during feeding, and can hold 1,000 tons or more of food and water when fully expanded. By taking tonnes of water into its mouth and filtering out the fish or krill with its baleen plates a medium-sized Blue whale can eat over 4 tons of krill a day.

The head of the Blue whale forms up to a quarter of the total body length and compared with other rorquals is very broad. It has twin blowholes with exceptionally large fleshy splashguards to the front and sides. The dorsal fin is small and triangular with a tip which may be rounded or pointed. It is set three-quarters of the way back and can be moderately falcate. The baleen plates in the mouth of the Blue whale can be 90cm-1m (35-39in) in length the longest of all the rorquals but not the longest of all whales.

The underside of the whale is yellow or mustard-coloured and is not a natural pigmentation but is caused by the presence of algae, called diatoms, which attach themselves to the whale's body. This is most commonly observed in animals living in cold waters near the poles. It has broad flukes with slightly concave or straight trailing edges and a small notch in the middle. The flippers are long and slender and about one seventh of body length.

The blow is spectacular, rising to 9 metres (30ft) high it is a slender, straight column. Breathing sequence usually involves 2-6 minutes at the surface, blowing once every 10-20 seconds, followed by a dive for 5-20 minutes. The fin is visible briefly before the whale arches its back in preparation for the dive. Its tail stock may arch and its flukes may be visible but often they simply sink below the surface.

Blue whales rarely ever breach clear of the water. Juveniles have been observed breaching and landing on their sides or stomachs. Some individuals are easy to approach while others can be difficult. The whale can accelerate to speeds of over 30km/h (19mph) when chased, but usually much slower, and can dive to depths of 150m (490ft) or more.

Most Blue whales live in the Southern Hemisphere while smaller populations inhabit the North Atlantic and North Pacific. They migrate long distances between low latitude winter mating grounds and high latitude summer feeding grounds and are often seen in parts of California, Gulf of California (Sea of Cortez), Gulf of St. Lawrence, Canada and the northern Indian Ocean. Before mans intervention there were 228,000 Blue whales swimming the oceans of the world. Between 1904 and 1978, whalers scoured the seas for this huge cetacean, most were taken in the southern hemisphere, many against the law. Current figures suggest that a mere 11,700 animals are left. As the population figure suggests, it was ruthlessly and relentlessly slaughtered for every reason imaginable, almost to the point of extinction. Now on the endangered list, the Blue Whale is protected (since 1967) worldwide by international law. It is not to be hunted by anyone for any reason at all. Suggestion are that some populations may never recover.