Blue Whale - Photo: unknown

Blue Whale – Photo: unknown

Latin name: Balaenoptera Musculus

Longevity: Approximately 80 years.

Estimated Current Population: < 5,000 animals.

CITES Clasification: Endangered.

The Blue Whale is found throughout every ocean in the world, from the equator to the polar regions in both the Southern and Northern Hemispheres. They migrate to polar waters in summer for feeding and return to warmer seas in winter for breeding – thus covering thousands of kilometres every year. The subspecies, the Pygmy Blue Whale (Balaenoptera musculus brevicauda) is found mainly in the Southern Hemisphere.

Classification

Linnaeus classified the Blue Whale in 1758, calling it Balaenoptera musculus, meaning ‘Little Mouse’. The name Balaenoptera musculus musculus is given to Blue Whales inhabiting the Northern Hemisphere, whilst those occupying the Southern Hemisphere are known as Balaenoptera musculus intermedia. In 1963 a smaller subspecies, Balaenoptera musculus brevicauda (Pygmy Blue Whale) was recognized.

Local Names

Sulphurbottom (referring to the yellow-brown appearance of algae on the skin after the whales have inhabited polar waters); Sibbald’s Rorqual; Great Northern Rorqual.

Description

This is a streamlined and slender whale, with a small dorsal located about three-quarters of the way along the back. The tail flukes are large and notched, and flippers are slender and pointed. It is darkish blue-grey in colour, with a mottled appearance and a pale underside with 55-88 throat grooves. The Blue Whale is about 25-26.5m in length, but the longest recorded was 31m, with females are generally larger than males. It weighs between 100-120tonnes, the heaviest recorded was a female weighing 200tonnes. There are about 540-790 coarse black baleen plates per animal, each about 1m in length.

Recognition at Sea

Any rorqual exceeding 24m is likely to be a Blue Whale. The dorsal fin is not immediately obvious because of its position. The Blue Whale’s blow is vertical, measuring about 9m in height.

Habitat

Blue Whale Habitat

Blue Whale Habitat

This species is rarely seen near the coast, except in polar regions when it follows the retreating ice-edge. This in turn can cause entrapment by ice as the weather changes, which is frequently recorded in the Gulf of St Lawrence in Canada.

Food & Feeding

The main stomach of the Blue Whale can hold a tonne of its primary food source, euphausiids (tiny plankton), which it specialises in consuming in the Antarctic. Since euphausiids are also the primary food for Fin, Sei and Minke Whales, the Blue Whale is in direct competition with these species for food.

Behaviour

Blue Whales are not strictly gregarious in manner, and is usually found either in pairs (as in mother and calf) or as a solitary animal. However, this species has been found to congregate on the feeding grounds, and do not, as a rule, dive deeply (maximum 200m). Moans, pulses, clicks, rasps and buzzes, as well as breaching and lob-tailing are the primary means of communication between individuals.

The Influence of Man

Once fast catcher boats and explosive harpoons became available in the latter half of the 1800s, all rorquals were catchable and, as the largest was most profitable, the Blue Whale became the primary target. Catches were made primarily on the summer feeding grounds – the North Atlantic, Northe Pacific and mostly, the Antartic Ocean. Nearly 30,000 animals were taken in 1930, and the raw churning power of the largest creature in existence almost left the planet forever. By 1966 when the species received global protection only a century after it became the most hunted creature on Earth, over a third of a million Blue Whales had been slaughtered.