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.

FIN WHALE Balaenoptera physalus

Fin Whales are second only to Blue Whales in length and weight. They are perhaps the fastest of the great whales with a wedge-shaped head with a flat top marked only by a single median ridge ending at the blowhole. The flippers are comparatively small, about 12 per cent of body length; and the fin, placed about 65 per cent of the way back, is 60 cm (less than 2 ft) high, leaning steeply backwards. There are 50-86 (average 64) deep grooves in the throat, beginning on the tip of the jaw and running back just beyond the midpoint of the body. From there back to the flukes, the Fin Whale is extraordinarily compressed from side to side, forming a sleek outline which, even when accurately portrayed, seems hopelessly exaggerated.

Description: Large; length averages 21 m (70 ft) for males, with a maximum of about 25 m (82 ft), and 22 m (73 ft) for females, with a maximum of about 26.8 m (88 ft); calves are about 6.5 m (22 ft) at birth. Weight averages 35,000 45,000 kg (40-50 tons) for both sexes, with a reported maximum of over 69,500 kg (76 tons); calves are about 3,600 kg (4 tons) at birth.

The colour pattern is unique. As in many other whales, the body of the Fin is counter shaded, with a dark grey or umber brown back and a light or white underside; but on the head this system is rotated through 90°. The colour seems to have shifted entirely to the left, leaving the right lower jaw, the right baleen plates and even the right side of the tongue, pale and unpigmented. There are also distinctive white areas on the underside of the flippers and flukes. This asymmetry may have something to do with feeding habits. Behind the head is a pale grey chevron on the back with arms pointing toward the tail; and, leading backwards from the eye, 2 lines: a dark one running up on to the back and a light one arching over to the insertion of the flipper and sometimes continuing up on to the flank.

Fin Whales show none of the whitish mottling charac¬teristic of the Blue Whale.
Field Identification All rorquals are easily identified by the small dorsal fin placed well back on the body. The difficult part is distinguishing one species of Balaenoptera from another when only the back and the fin can be seen. Typically Fin Whales (B. physalus) rise obliquely to the surface so that the top of the flat head breaks water first. After breathing, there is a slow roll of smooth dark back bringing the fin into view. With Blue Whales (B. musculus 6) the roll lasts longer, until finally the tiny fin can be seen, whilst with Sei Whales (J3. borealis 8), the fin appears almost simultaneously with the blow. A young Fin Whale and a Tropical Whale (B. edeni) of comparable size are almost impossible to tell apart in this way, except that the Tropical Whale's fin is a little more sharply pointed. The breathing and diving sequence is almost invariable.

First the blow is visible, a single tall column of spray 4-6 m (13-20 ft) high, widening at its crown into an ellipse. Then the long slow, fairly shallow roll ending with the fin, repeated 4 or 5 times at intervals of 10-20 seconds; in the last roll of the series the back is arched more steeply, rising at least twice the height of the fin above the water, before a deep dive usually lasting 5-15 minutes, but it can be longer. Fin Whales dive to depths of over 250 m (820 ft) and can stay down as long as 26 minutes. The tail flukes never show in surface rolls, but may just break the surface prior to sounding.

At close range the slightly fishy smell of the whale's breath is apparent and it is possible to hear the deep rich whistling sound of the air intake. Fin Whales sometimes breach, falling back with a resound¬ing splash, never re-entering smoothly headfirst as Piked Whales do. Fin Whales can move very fast, up to 40 kph (over 20 knots) and are so strong that, before diesel-powered catchers and explosive harpoons, they were beyond the reach of whalers.

Fin Whales are occasionally beached. If this is recent, the white right-hand side of the lower jaw makes identification easy. Even when the skin has darkened the difference in colour of the baleen remains striking. There are 260-480 (average 360) baleen plates Each is short, less than 90 cm (3 ft) long, but larger and broader than those of any right whale. Those on the left of the jaw are blue grey in colour, while those of the front third on the right side are white. In all cases the feathery bristles are yellowish. It is said that Fin Whales in the North Pacific may have shorter and coarser baleen.

There are large numbers of presumably tactile hairs along both jaws, with a beard-like concentration on the tip of the lower one. There are few ectoparasites, although barnacles and whale lice (Cyamus balaenopterae) may be found.

The skull, as in all Balaenoptera, is birdlike and hardly arched. The brain weighs approximately 8.5 kg (over 18 lb). There are 60--63 vertebrae, those in the neck usually free, but sometimes the first 2 or 3 may be partly fused. The flippers have 4 fingers.
Fin Whales are generalist feeders. Their sta¬ple diet is krill, though where swarming crustaceans or schools of small fish have been driven into compact masses, a Fin Whale will advance on them at speed and, as it approaches, roll on to its right side at the surface, left flipper in the air. Then with its mouth wide open and throat distended, the whale pivots on its submerged right flipper, making a massive lateral scoop, which is highly productive because the shoaling prey invariably try to escape by doubling back around the approaching whale rather than diving beneath it.

The peculiar lopsided pigmentation on the Fin Whale's head makes sense: by turning on to its right side, the whale once again acquires the usual obliterative colora¬tion (dark above and pale below) that helps to camouflage all animals living in an exclusively top-lit environment. The exis¬tence of this unique adaptation suggests that the Fin Whale prefers prey with good vision, i.e. fish rather than plankton. The two species which feed most heavily on krill (Blue Whales and Sei Whales) are the only ones in which the basic body colour is broken up by disruptive spotting, so that in the murky Antarctic waters they tend to look less like approach¬ing predators than harmless spotty patches of plankton.

These are the most common large baleen whales and tend to be more gregarious than other species. It is still possible to see concentrations of 100 or more on favourite feeding grounds. The normal social unit is a pod of 6-15 individuals, including one or more adult males. The age of maturity has been depressed by whaling to about 6 years for males (at 17 m or 57 ft long), and 7 years for females (18 m or 60 ft long).
Mating occurs in winter in warmer waters to the accompaniment of social play and ponderous courtship; gestation lasts almost a year and so the young tend to be born in the same areas the following year. Suckling lasts for 6 months, when the calf doubles its length to 12 m (40 ft). Females calve in alternate years. Fin Whales may live for 100 years.