This site is indebted to the writings of Lyall Watson (amongst others), for his amazing and well-researched book Whales of the World, illustrated by Tom Ritchie.

BLUE WHALE - Balaenoptera musculus

The most common English name is sulphur-bottom, which is based on the fact that in extended stays in colder water this whale picks up a film of yellow-green diatoms which conceal its natural hue.  It is possible that 3 distinct subspecies of Blue Whale exist, a smallish one in the northern hemisphere, a larger form that spends the Southern summer in Antarctic waters and a possible Pygmy Blue Whale said to be confined to the area around Kerguelen and Crozet islands in the southern Indian Ocean.

 Description: Very large; length averages 25 m (82 ft) for males, with a maximum recorded of 31 m (102 ft), and 26 m (85 ft) for females, 80,000-130,000 kg (90-144 tons) for both sexes. Calves are about 7 m (23 ft) long and weigh about 7,250 kg (8 tons) at birth.
The Blue Whale's shape is long and streamlined, with the head being about 25 per cent of its total length. The rostrum is broad and level and, from above, shaped like a slightly flattened Gothic arch. There is a single ridge extending from the sharply raised area of the blowholes to almost the snout. The fin is small, low, set very far back (about 30 cm or 1 ft high), and is triangular or hook-shaped. The flippers are relatively short and tapered. There are 64-94 grooves on the throat, extending for approximately 60 per cent of body length and ending beyond the navel.

The overall colour is marine blue grey, mottled with light grey and white while flipper tips and undersides are much lighter. The shade of blue varies with individuals and probably darkens with age. The pygmy Blue Whales of Kerguelen Island in the Indian Ocean are said to be more silvery grey in colour, with a shorter tail and a proportionately longer and heavier trunk. They may also be extensively scarred.

Identification: Despite their enormous weight, Blue Whales give an impression of sleek grace in water, making it easy to underestimate their size.
The blow is strong, blasting up in a single, thin column 6-12 m (20-40 ft) high. Breathing rhythms vary with activity, but the most familiar is several (up to 20), shallow dives at intervals of about 20 seconds, followed by a longer deeper dive of up to half an hour.
Between some shorter dives, the whale surfaces almost horizontally so that the blowhole and much of the back appear at the same time. Usually the blowhole and part of the head surface first, the whale spouts, then reveals a long expanse of back sliding slowly over until the tiny fin emerges briefly just before the tail touches the surface.

The fluke exposure is fleeting, unlike the high, flapping dive of Great Right, Humpback and serves as a useful distinction. Distinguishing Blue from Fin whales is more difficult: In side view, the skull is very much like that of the Fin Whale, but it is broader above. There are 63-64 free vertebrae.

B. musculus broad U-shaped head; mottled blue back; tiny fin visible long after the blow; comparatively low roll; it often shows its flukes before diving.
B. physalus narrow V-shaped head; grey back; larger fin visible shortly after blow; it rolls high out of the water; it seldom shows flukes before diving.
Blue whales are shyer than other rorquals. They normally cruise at 6-8 kph (3-4 knots), but sound easily when disturbed and, when harried, accelerate rapidly to speeds of 20-30 kph (10-16 knots).

The baleen is all black. There are 270-400 (average 324) pure black and roughly triangular plates on each side of the jaw. These are about 100 cm (40 inches) long and 55 cm (20 inches) wide. There is a rudimentary moustache of 4 bristles and a sparse adolescent beard of 40 long hairs.

Crustacean parasites often live in the baleen while there are a few barnacles and some whale lice on the skin around the mouth, eyes and genital slit. A common skin parasite is a strange crustacean called Penella, which protrudes like a small soft paint brush or algal frond from beneath the blubber. Most of these ectoparasites seem to be picked up in tropical waters, and as the whales migrate to cooler areas, they tend to drop off.

Natural History: Blue Whales eat swarming planktonic creatures, but unlike Fin Whales are selective feeding almost exclusively on a few species. In the Antarctic they seem to eat nothing but krill, with the accidental inclusion of a few small fish.
All these crustaceans concentrate in shoals in brightly lit waters, less than 40 m (130 ft) from the surface. In areas of turbulence or upwelling, krill reach a density of more than 15 kg/m3 (about Ilb/h"). Blue Whales swallow about 4,000 kg (over 4 tons) of this rich bisque each day, which in the Antarctic (where krill weigh about 1 g apiece) means 4 million shrimps.

The krill season lasts for about 120 days, after which the icepack covers the feeding grounds and the whales migrate towards the equator. There are subtropical and even tropical areas rich in plankton, which attract other baleen whales in winter months, but seem to be of no interest to Blues, who eat little or nothing in warmer waters. Because the Blue Whales feed largely at the surface, it is often difficult to decide whether they are cruising along in a series of shallow dives or actually eating.

Little is known of the Blue Whale's voice except that it produces ultrasonic bursts of sound while feeding. These are pulses of 21-31 kHz similar to those used by smaller toothed whales for echolocation. They could help to find concentrations of krill. Low-frequency moans lasting over 30 seconds and broken into three parts have been recorded off the coast of Chile.