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BLUE WHALE Balaenoptera musculus

Meaning of scientific name: mouse-like finned whale (many think the name was meant as a joke, since blue whales are so large).

On land an animal the size of a blue whale would be crushed by its own weight without the support of large heavy bones. Because its body is supported by water, as a sea animal, the need for heavy bones to support its weight disappeared. These, plus the availability of a large food supply, have made it possible for the blue whale to reach such an enormous size.

The blue whale makes deep and rumbling sounds that can be felt as much as heard. These low-frequency sounds travel long distances through water, allowing blue whales to communicate with each other over hundreds of miles of ocean.

What does it look like?

The blue whale is the largest mammal, possibly the largest animal, to ever inhabit the earth. Its body is long, somewhat tapered, and streamlined, with the head making up less than one-fourth of its total body length. Its rostrum (upper part of the head) is very broad and flat and almost U-shaped, with a single ridge that extends just forward of the blowholes to the tip of the snout.

Its blowholes are contained in a large raised "splash guard," and the blow is tall and straight and over 20 feet high. Its body is smooth and relatively free of parasites, but a few barnacles attach themselves to the edge of the fluke and occasionally to the tips of the flippers and to the dorsal fin. There are 55-68 ventral grooves or pleats extending from the lower jaw to near the navel.

The blue whale is blue-gray in color, but often with lighter gray mottling on a darker background (or with darker spots on a lighter background). The underside of its flippers may be a lighter color or white, while the ventral (underside) of the fluke is dark. The blue whale acquires microorganisms called diatoms in the cold waters of the Antarctic and North Pacific and North Atlantic, which give the underside of its body a yellowish green caste. Because of this yellow color, the early whalers gave it the name "sulphur bottom."

An average blue whale is between 75 and 80 feet long, and weighs about 110 tons. Females are larger than males of the same age, the largest perhaps weighing as much as 150 tons.

Where does it live?

Blue whales may be found in all oceans of the world. Blue whales migrate long distances between equatorial wintering grounds and high latitude feeding areas. In the eastern North Pacific, they winter off southern and Baja California. During the summer they may be found across the Gulf of Alaska, but they seldom enter the eastern Bering Sea.

Historical areas of concentration include the eastern Gulf of Alaska, the eastern Aleutians, and the far western Aleutians. Blue whales spend most of their time along the edges of continental shelves and are seldom seen in coastal Alaska waters.

They mate and calve in tropical-to-temperate waters during winter months and feed in polar waters during summer months. Blue whales in the northern hemisphere move north to Arctic waters to feed; blue whales in the southern hemisphere move south to the Antarctic to feed. Nearly all the southern hemisphere population may be found in the summer feeding grounds in the Antarctic.

Though they may be found singly or in small groups, it is more common to see blue whales in pairs. They are sometimes seen in larger groups and loosely defined concentrations of 50-60 have been observed. They are fast, strong swimmers, capable of reaching 30 mph when alarmed, but they usually cruise along at about 12 mph.

What does it eat?

The blue whale is thought to feed almost exclusively on small, shrimp-like creatures called euphausiids or krill. During the summer feeding season the blue whale gorges itself, consuming an astounding 4 tons or more each day. This means it may eat up to 40 million krill a day. As a baleen whale, it has a series of 260-400 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 plates are black and measure about 20 inches in length toward the front of the mouth and about 40 inches at the rear.

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 Breading

Recent research indicates that blue whales reach sexual maturity between the ages of 6-10 years, or when males average about 74 feet and females are about 79 feet. Calves are born at intervals of 2 to 3 years and gestation is about 12 months. Calves are 23 to 27 feet long at birth and 3 tons. Calves nurse for 7 to 8 months and are weaned when they reach 52 feet in length. At that time they weigh about 23 tons. During the nursing period, calves consume 100 gallons of the fat-rich mother's milk each day, gain 200 pounds a day, or 8 pounds an hour, and grow 1 and 1/2 inches in length a day!

The Threat to Their Survival

Because of their enormous size and speed, blue whales were safe from early whalers, who could not pursue them in open boats with hand harpoons. But in 1868 a Norwegian, Sven Foyn, revolutionized the whaling industry with the invention of the exploding harpoon gun and by using steam and diesel powered factory ships and catcher boats. He also perfected the technique of inflating dead whales with air so they wouldn't sink after being harpooned. The whaling industry began to focus on blue whales after 1900. A single 90-foot blue whale could yield up to 120 barrels of oil, and the blues were killed by the thousands.The slaughter peaked in 1931 when over 29,000 were killed in one season.

Protection

Blue whales became so scarce that the whalers turned to other species and, belatedly, the International Whaling Commission (IWC) banned all hunting of blue whales in 1966 and gave them worldwide protection. Recovery has been extremely slow, and only in the last few years have there been signs that their numbers may be increasing. Pre-whaling numbers have been estimated at 200,000, and though exact figures are not known, an estimated 5,000 survive today in three populations: North Atlantic, North Pacific, and the Southern Hemisphere. No human activities in the North Pacific, other than whaling, are known to have affected the species. Therefore, other management actions are unlikely to contribute substantially to recovery.

Sources

Balcomb, K. and S. Minasian. 1984. The World's Whales. Smithsonian Books. W. W. Norton, New York.

Ellis, R. 1980. The Book of Whales. Alfred A. Knopf, New York.

http://www.marinemammalcenter.org/learning/education/whales/blue. Whales dolphins and porpoises - Cetaceans: Blue Whales. The Marine Mammal Center. 2002.

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