Fin Whale - Description and Behavior

Description and Behavior

The fin whale is usually distinguished by its tall spout, long back, prominent dorsal fin, and asymmetrical coloration. In the Northern Hemisphere, the average size of adult males and females is about 18.5 m (60 ft) and 20 m (65 ft), while in the Southern Hemisphere it is 20.5 m (67 ft) and 22 m (72 ft). In the North Atlantic, the longest reported was 24.5 m (80' 6" ft) (albeit what whalers' called a "bastard", a possible blue/fin hybrid), while the longest measured by True (1904) was 21.5 m (70' 8" ft), both females. In the North Pacific, the longest reported were 22.9 m (75 ft) for males and 24.7 m (81 ft) for females, while the longest reliably measured were 20.8 m (68 ft) and 22.9 m (75 ft), respectively. In the Southern Hemisphere, the longest reported for each sex were 25 m (82 ft) and 27.3 m (89' 6" ft), while the longest measured by Mackintosh and Wheeler (1929) were 22.4 m (73' 7" ft) and 24.5 m (80' 5" ft); although Major F. A. Spencer, while whaling inspector of the factory ship Southern Princess (1936-38), confirmed the length of a 25.9 m (85 ft) female caught in the Antarctic south of the southern Indian Ocean. The largest fin whale ever weighed (piecemeal) was a 22.7 m (74.5 ft) pregnant female caught by Japanese whalers in the Antarctic in 1948 which weighed 69.5 tonnes (68.4 long tons; 76.6 short tons), minus 6% for loss of fluids during the flensing process. It is estimated that an individual over 27 m (89 ft) would weigh in excess of 120 tonnes (120 long tons; 130 short tons). Full physical maturity is attained between 25 and 30 years. Fin whales live to 94 years of age, although specimens have been found aged at an estimated 135–140 years. A newborn fin whale measures about 6.5 metres (21 ft) in length and weighs approximately 1,800 kilograms (4,000 lb). The animal's large size aids in identification, and it is usually only confused with the blue whale, the sei whale, or, in warmer waters, Bryde's whale.

The fin whale is brownish to dark or light gray dorsally and white ventrally. It has paired blowholes on a prominent splashguard, and a broad, flat V-shaped rostrum. Two lighter-colored chevrons radiate from the eyes and curve forward, joining to form a V-shape oriented towards the head. Its lower jaw (and occasionally upper jaw) is white, while the left side of the jaw is gray or black. This type of asymmetry is seen in Omura's whale and occasionally in minke whales. It was hypothesized to have evolved because the whale swims on its right side when surface lunging and it often circles to the right while at the surface above a prey patch. However, the whales just as often circle to the left. There is no accepted hypothesis to explain the asymmetry.

The whale has a series of 56–100 pleats or grooves along the bottom of the body that run from the tip of the chin to the navel that allow the throat area to expand greatly during feeding. It has a curved, prominent dorsal fin that ranges in height from 26–75 centimeters (10–30 in) (usually 45–60 centimeters (18–24 in)) and averages about 51 centimetres (20 in), lying about three-quarters of the way along the back. Its flippers are small and tapered, and its tail is wide, pointed at the tip, and notched in the centre.

When the whale surfaces, the dorsal fin is visible soon after the spout. The spout is vertical and narrow and can reach heights of 6 metres (20 ft) or more. When feeding, they will blow 5-7 times in quick succession, but while traveling or resting will blow a single time every minute or two. On their terminal (last) dive they arch their back high out of the water, but rarely raise their flukes out of the water. It then dives to depths of up to 470 metres (1,540 ft) when feeding or only a few hundred feet when resting or traveling. The average feeding dive off California and Baja lasts 6 minutes, with a maximum of 17 minutes; when traveling or resting they usually dive for only a few minutes at a time. Fin whales rarely breach.

The fin whale is one of the fastest cetaceans and can sustain speeds of 37 kilometres per hour (23 mph) and bursts in excess of 40 kilometres per hour (25 mph) have been recorded, earning the fin whale the nickname "the greyhound of the sea". Fin whales are more gregarious than other rorquals, and often live in groups of 6–10, although feeding groups may reach up to 100 animals.