Fin Whale

Balaenoptera physalus

Fin WhaleClass: Mammalia
Order: Cetacea
SubOrder: Mysticeti
Family: Balaenopteridae
Genus: Balaenoptera
Species: Physalus

Physical Description
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 35 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.

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.

Length & Weight
Adult males measure up to 24m in the northern hemisphere, and 27m in the southern hemisphere. Females are slightly larger than males. Weight for both sexes is between 45-63 tonne.

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 5.5 -6.5m and weight is 1.8 tonne. Calves nurse for 6-8 months and are weaned when they are 10-12m in length.

Fin whales feed mainly on small shrimp-like creatures called krill 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 tonne 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 75 cm in length and 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.

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 is5-8 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 550m.

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.

Australian Museum; American Cetacean Society; National Geographic Society; Department of the Environment, Water, Heritage and the Arts