Whale

I

Introduction

Whale, large mammal that lives its entire life in the water. Whales have a fishlike body; however, their tail fins, called flukes, are horizontal rather than vertical, and they have paddlelike front limbs, called flippers. Their skin is smooth and glossy and, depending on the species, may be black, white, or a variety of colors and patterns. Beneath the skin is a thick layer of fat, called blubber, which provides insulation and serves as a source of stored energy.

Whales resemble fish in many ways, but they are not fish. Fish are cold-blooded and breathe underwater using gills; whales, on the other hand, maintain a warm and constant body temperature of about 37°C (about 99°F) and breathe air with lungs. Unlike fish, which move their vertical tail fins from side to side when they swim, whales move their horizontal tail fins up and down to propel themselves through the water.

Whales belong to the mammalian order Cetacea. Scientists classify whales into two groups. One group, known as the Odontoceti, or toothed whales, have jaws lined with pointed teeth that they use in hunting fish, squid, and other prey. Toothed whales also include dolphins and porpoises. The other whale group, called the Mysticeti, or baleen whales, lack teeth. These whales use giant, flexible combs of a material called baleen to filter small fish and tiny crustaceans from the water.

Whales are found in all the world's oceans and even in a few rivers. One species of dolphin, the pink river dolphin, lives only in the Amazon River and its larger tributaries. Some whales, including the blue, fin, humpback, and gray, undertake some of the longest migrations in the animal kingdom, traveling between the tropics in winter and subpolar waters in summer. Other whales do not migrate long distances or, like the killer whales, wander without specific migratory routes.

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II

Bodies of Whales

Whales are enormous in size compared to all other animals. The blue whale is one of the largest animals that has ever lived, reaching a length of over 24 m (80 ft) and a weight of 150 metric tons. Its heart is as big as a Volkswagen Beetle, and its body is almost as large and about as heavy as that of the largest known dinosaur.

Whales have a streamlined, rounded body tapering in the rear to a pair of broad horizontal tail flukes that provide the main propulsive thrust for swimming. They have paddle-shaped flippers that help stabilize and steer the whale while swimming. The bones of the flippers resemble the jointed limbs and digits of land mammals. Many whales have a dorsal fin located at or behind the center of the back.

A

Skin

A whale’s skin feels much like smooth, wet rubber to the touch. The skin has no sweat glands or oil glands, and it is nearly devoid of hair. Beneath the skin is a thick layer of fat called blubber that aids in buoyancy, serves as a source of stored energy, and helps preserve body heat. Blubber permits whales to stay warm even in near-freezing waters.

B

Blowhole and Lungs

Whales do not breathe through their mouths, but rather through a nostril, or blowhole, located on the top of the head. Toothed whales have only a single blowhole; baleen whales have two blowholes. The blowhole opens by a slight muscular contraction and closes automatically when the muscle relaxes. As a whale surfaces it exhales through the blowhole, creating a loud sound and characteristic cloud of mist known as the spout. The spout is caused by condensation from the exhaled warm, moist air, not from seawater trapped in the blowhole, as was once believed.

Air taken in through the blowhole travels through the trachea (windpipe) to the lungs. Unlike for most land animals, the trachea does not connect to the throat. So when the whale opens its mouth underwater to feed, water does not rush into the lungs as it would in land animals. This structural arrangement enables the whale to breathe air and swallow food at the same time.

The lungs transfer oxygen to the blood while removing the blood’s carbon dioxide. Relative to body size, whale lungs are proportionally somewhat smaller than human lungs. But whale lungs are far more efficient: While human lungs exchange about 15 to 20 percent of their contents with each breath, whale lungs exchange about 90 percent with each breath. This means that whales can take up oxygen and dispose of carbon dioxide much faster than humans, enabling them to hold their breath underwater for long periods.

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