Fin Whale

CLASS: Mammalia
ORDER: Cetacea
SUBORDER: Mysticeti
FAMILY: Balaenopteridae
GENUS: Balaenoptera
SPECIES: physalus

The fin whale is one of the rorquals, a family that includes the humpback whale, blue whale, Bryde's whale, sei whale, and minke whale. Rorquals all have a dorsal fin and throat grooves that expand when the animal is feeding. The fin, or finback whale is second only to the blue whale in size and weight. Among the fastest of the great whales, it is capable of bursts of speed of up to 23 mph (37 km/hr) leading to its description as the "greyhound of the sea." Its most unusual characteristic is the asymmetrical coloring of the lower jaw, which is white or creamy yellow on the right side and mottled black on the left side. Fin whales are found in all oceans of the world, though they seem to prefer temperate and polar waters to tropical seas.

Physical Description

The fin whale is long, sleek, and streamlined, with a V-shaped head which is flat on top. A single ridge extends from the blowhole to the tip of the rostrum (upper jaw). There is a series of 50-100 pleats or grooves on the underside of its body extending from under the lower jaw to the navel.

Surface Characteristics

Color

The fin whale is light gray to brownish-black on its back and sides. Two lighter "colored" chevrons begin midline behind the blowholes and slant down the sides towards the fluke (tail) before turning and ending right behind the eye. The underside of its body, flippers, and fluke are white. The lower jaw is gray or black on the left side and creamy white on the right side. This asymmetrical coloration extends to the baleen plates as well, and is reversed on the tongue.

Fins and Fluke

The fin whale has a prominent, slightly falcate (curved) dorsal fin located far back on its body. Its flippers are small and tapered, and its fluke is wide, pointed at the tips, and notched in the center.

Length and Weight

Adult males measure up to 78 feet (24 m) in the northern hemisphere, and 88 feet (26.8 m) in the southern hemisphere. Females are slightly larger than males. Weight for both sexes is between 50-70 tons (45,360-63,500 kg).

Feeding

Fin whales feed mainly on small shrimp-like creatures called krill or euphausiids and schooling fish. They have been observed circling schools of fish at high speed, rolling the fish into compact balls then turning on their right side to engulf the fish. Their color pattern, including their asymmetrical jaw color, may somehow aid in the capture of such prey. They can consume up to 2 tons (1,814 kg) of food a day. As a baleen whale, it has a series of 262-473 fringed overlapping plates hanging from each side of the upper jaw, where teeth might otherwise be located. These plates consist of a fingernail-like material called keratin that frays out into fine hairs on the ends inside the mouth near the tongue. The baleen on the left side of the mouth has alternating bands of creamy-yellow and blue-gray color. On the right side, the forward 1/3 section of the plates is all creamy-yellow. The plates can measure up to 30 inches (76 cm) in length and 12 inches (30 cm) in width. During feeding, large volumes of water and food can be taken into the mouth because the pleated grooves in the throat expand. As the mouth closes water is expelled through the baleen plates, which trap the food on the inside near the tongue to be swallowed.

Mating and Breeding

Adult males reach sexual maturity at about 6-10 years of age. As in some other whales, sexual maturity is reached before physical maturity. Gestation is 12 months, and calves are believed to be born at 3-4 year intervals. Length at birth is 14-20 feet ( 5.5 -6.5 m) and weight is 2 tons (1,814 kg). Calves nurse for 6-8 months and are weaned when they are 30-40 feet (10-12 m) in length.

Range Map

Distribution and Migration

Fin whales are found in all oceans of the world. They may migrate to subtropical waters for mating and calving during the winter months and to the colder areas of the Arctic and Antarctic for feeding during the summer months; although recent evidence suggests that during winter fin whales may be dispersed in deep ocean waters.

Natural History

Fin whales are found most often alone, but groups of 3-7 individuals are common, and association of larger numbers or concentrations may occur in some areas at times. Because their powerful sounds can carry vast distances, fin whales may stay in touch with each other over long distances. The fin whale's blow is tall and shaped like an inverted cone, and the dive sequence is 5-8 blows approximately 70 seconds apart before a long dive. They rarely raise their flukes as they begin their dive, which can be as deep as 1,800 feet (550 m).

Status

The fin whale's speed, plus the fact that they prefer the vastness of the open sea, gave them almost complete protection from the early whalers. With modern whaling methods, however, finback whales became easy victims. As blue whales became depleted, the whaling industry turned to the smaller, still abundant fin whales as a replacement. As many as 30,000 fin whales were slaughtered each year from 1935 to 1965. The International Whaling Commission (IWC) placed them under full protection in 1966 beginning with the North Pacific population. Precise estimates are unavailable today, but it is thought that present populations are about 40,000 in the northern hemisphere and 15,000-20,000 in the southern hemisphere, a small percentage of the original population levels.

Bibliography

Gambell, R. 1985. in Handbook of Marine Mammals (Ridgway & Harrison Eds.). Academic Press. pp.171-192
Jefferson, T.A., M.A. Webber, R.L. Pitman. 2015. Marine Mammals of the World: A Comprehensive Guide to their Identification, 2nd edition. Elsevier/AP.

Acknowledgements

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