WHALES

I - GENERAL INFORMATION ON WHALES
Whale, large mammals that live their entire lives in the water. Like other mammals, whales have large, highly developed brains and nurse their young with milk. Among aquatic mammals, whales are the most completely adapted to life in the water. 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, whales move their tails up and down instead of side to side when they swim. Whales are enormous in size compared to other mammals. The blue whale is probably the largest animal that has ever lived, reaching a length of nearly 30 m (100 ft) and a weight of 180 metric tons. Its heart is as big as a Volkswagen Beetle and its body is larger and heavier than that estimated for any known dinosaur. The blue whale makes the loudest sound (over 150 decibels) of any animal, and can be heard over thousands of kilometers across entire oceans. Certain other whales, especially the dolphins, emit clicking sounds that bounce off objects. The returning echo is used as a sonar image of their underwater surroundings. They share this ability, called echolocation, with bats, shrews, and a few kinds of birds. 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 better-known whales, including the blue, finback, humpback, and gray whale, range widely and migrate between the tropics in winter and subpolar waters in summer. Humpbacks have separate populations in the northern and southern hemispheres and do not seem to cross the equator. Sperm whales and killer whales, or orcas, are wanderers without specific migratory routes. An individual sperm whale might, in its lifetime, swim around the world.
II - TYPES OF WHALES
There are at least 75 species of whale, each with its own unique characteristics. Whales range from black to white in color and from nearly 30 m (100 ft) to less than 2 m (7 ft) in size. They may live in saltwater or freshwater, and can be found as far north as the Arctic Circle, and as far south as Antarctica. The most common way of classifying whales, however, is according to their feeding strategy. One group of whales has teeth, and the other does not. AToothed Whales The toothed whales have jaws lined with simple, pointed teeth. These whales actively hunt fish, squid, and other prey. Toothed whales vary in size from small harbor porpoises less than 2 m (6 ft) long to the great sperm whales, whose adults average 17 m (55 ft) long and weigh nearly 50 metric tons. Among the more unusual toothed species are the narwhal and the beluga, both inhabiting Arctic waters. The male narwhal possesses a single ivory tusk that grows almost 2.5 m (8 ft) long, straight forward from its head. Adult belugas are completely white and resemble large dolphins with rounded foreheads. Most dolphins are 2 to 4 m (7 to 13 ft) long and possess an elongated beak, or rostrum. Killer whales are the largest of the dolphins, growing up to 8 m (25 ft) in length. Some dolphins, such as the Atlantic bottle-nosed dolphin, commonly live close to shore, while others, such as the Pacific spinner dolphin, live much of their lives far from land. There are two species of river dolphins, one from the Amazon River of Brazil and the other from the Ganges River of India. Both are nearly blind and find their way through murky waters using echolocation. BBaleen Whales Instead of having teeth, the baleen whales have mouths lined with giant, flexible combs of a material called baleen, or whalebone, which is used to filter small fish and crustaceans from the water. There are three types of baleen whales: the rorquals, the gray whales, and the right whales. The rorquals have narrow, streamlined bodies and are the fastest swimming whales. The giant blue and fin whales are rorquals as are their smaller relatives, the minke and sei whales. The sei whale can swim at more than 35 km/h (22 mph) over short distances. Some rorquals make annual long-distance migrations of thousands of kilometers. Gray whales live only in the North Pacific and measure up to 15 m (50 ft) in length. They are slow swimmers that stay near shallow waters where they can feed from the bottom. Right whales are thick-bodied, slow-swimming plankton feeders that reach 18 m (60 ft) in length. One right whale, the bowhead, lacks a dorsal fin, or back fin, enabling it to use its huge back to break through the thick Arctic ice for air. While not as fast as the rorquals, the gray and right whales are still capable of long-distance migrations.
III - ANATOMY OF WHALES
The streamlined body of whales appears remarkably fishlike. The front limbs are modified as paddle-shaped flippers and the broad horizontal tail flukes provide the main propulsive thrust. The whale's skeleton closely resembles the skeletons of other mammals. For instance, the bones of the flippers resemble jointed limbs and digits and the neck has exactly seven vertebrae. The whale's body is enveloped in 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. In warmer waters they are able to release heat like a radiator by controlling blood flow to the skin. A whale's skin is free of sweat glands and oil glands, is nearly devoid of hair, and feels much like smooth, wet rubber to the touch. Whales, like other mammals, have lungs. Whales do not breathe through their mouths, but rather through a nostril, or blowhole, located on the top of the head. The blowhole opens by a slight muscular contraction and closes automatically when the muscle relaxes. As a whale surfaces it exhales powerfully, creating a loud sound and a characteristic cloud of mist known as the spout. The spout is caused by condensation from the warm, moist air that is exhaled, not from seawater trapped in the blowhole, as was once believed. Large tail flukes provide thrust for whales when they swim. The power comes from body muscles that flex the lower spine up and down in a wavelike motion. The forelimbs of whales are flippers used for steering as the animals swim. In some species, such as humpbacks, the flippers are large and powerful and may be used for fighting among males. Whales are able to drink seawater and yet maintain the same low salt concentrations in their body fluids that other mammals do. For every liter of seawater a whale drinks, its highly efficient kidneys concentrate the salt into only two-thirds of a liter of urine for a gain of one-third liter of pure water. If a human were to drink a liter of seawater, it would require one and one-third liters of urine to remove the salt for a loss of one-third liter of water. Whales possess interesting adaptations for diving, some of which are shared with other aquatic mammals such as seals. Whales can store very high oxygen concentrations in their blood and muscles. During a dive, the heart rate slows and arteries constrict to many of the animal's organs, greatly reducing blood flow into those areas. This conserves oxygen and maintains the blood pressure to vital systems, especially the brain, sense organs, and to the heart itself. During a dive, the lack of oxygen triggers the build up of carbon dioxide and lactic acid in the blood and muscles. Unlike most animals, whales are able to resist pain and fatigue caused by lactic acid accumulation in muscle tissue. Baleen whales can hold their breath up to 50 minutes when diving, and of the toothed whales, the sperm whales can hold their breath up to 80 minutes. Whales have an excellent sense of hearing. They perceive sound that is waterborne and, as a result, they have been able to discard the external ear structures called pinnae that land mammals developed to gather airborne sounds. Whale external ears are reduced to small slits, but this does not hinder them from perceiving a wide range of sounds, many of which are not audible to humans.

DOLPHINS

I - GENERAL INFORMATION ON DOLPHINS
Dolphin, aquatic mammal closely related to whales and porpoises. Sleek and powerful swimmers found in all seas, dolphins are distinguished from porpoises by well-defined, beaklike snouts and conical teeth. The porpoise has a blunt snout, chisel-shaped teeth, and a stouter body. There are at least 32 species of dolphins. Typical examples are the bottle-nosed dolphin, a popular performer in seaquariums, and the common dolphin, which inspired many Mediterranean folk legends. Both often appear in open waters, making their characteristic arched bounds, frequently before the bow waves of ships. Several freshwater species inhabit river estuaries in Asia and South America. The small, graceful tucuxi dolphin, also known as the buffeo, or river dolphin, has been sighted more than 2000 km (more than 1250 mi) up the Amazon River. The tucuxi, the smallest dolphin, is less than 1.2 m (less than 4 ft) long; the largest, the bottle-nosed dolphin, reaches a length of 3 m (10 ft). The killer whale is considered a dolphin despite its much greater length of 9 m (30 ft). The pilot whale is also considered a type of dolphin. Dolphins once were hunted commercially, especially for the small quantity of valuable oil extracted from parts of the head and used to lubricate delicate watch mechanisms. Cheaper oils have now been found from other sources, and dolphins are no longer hunted for this reason. Many dolphins, however, become accidentally trapped and drowned in tuna nets; between 1959 and 1972 an estimated 4.8 million dolphins died in this way. Under pressure from animal rights activists and United States consumers, both domestic and international tuna canners have refused to accept shipments from fishing fleets that do not protect dolphins. Concern has also been expressed about the treatment of dolphins on display in public aquariums and in "swim with the dolphins" programs. The Marine Mammal Protection Act of 1972, amended in 1988 and 1992, was passed to prevent exploitation of dolphins and related aquatic animals. The National Marine Fisheries Service is the principal regulatory agency.
II - BEHAVIOR
In one day dolphins eat an amount of food, mostly fish and squid, equal to nearly one-third of their weight. Dolphins are swift enough to easily outdistance their prey. They seize their catches with jaws that have from 200 to 250 sharp teeth. Dolphins follow schools of fish in groups of varying size. Some species, such as the Pacific white-sided dolphin, make up aggregations estimated at tens of thousands of members. Less gregarious species, such as the bottle-nosed dolphin, join in groups that often contain only a few members. Dolphins, like whales, breathe through a blowhole at the top of the head. As they travel they break surface about every two minutes to make a short, explosive exhalation, followed by a longer inhalation before submerging again. The tail, like that of other aquatic mammals, strokes in an up-and-down motion, with the double flukes driving the animal forward; the flippers are used for stabilization. Dolphins are superbly streamlined and can sustain speeds of up to 30 km/h (up to 19 mph), with bursts of more than 40 km/h (more than 25 mph). Their lungs, which are adapted to resist the physical problems created for many animals by rapid changes in pressure, enable them to dive to depths of more than 300 m (more than 1000 ft). Adults of the bottle-nosed dolphin-the best-studied species-come to sexual maturity after 5 to 12 years in females and 9 to 13 years in males. They mate in the spring; after a gestation period of 11 or 12 months, a single calf is born, tail first. Calves swim and breathe minutes after birth; they nurse for up to 18 months. They are able to keep up with the mother by remaining close and taking advantage of the aerodynamic effects of the mother's swimming.
III - VOCALIZATIONS AND INTELLIGENCE
Dolphins almost constantly emit either clicking sounds or whistles. The clicks are short pulses of about 300 sounds per second, emitted from a mechanism located just below the blowhole. These clicks are used for the echolocation of objects and are resonated forward by the so-called oily melon, which is located above the forehead and acts as an acoustic lens. Echoes received at the area of the rear of the lower jaw are transmitted by a fat organ in the lower jaw to the middle ear. This echolocation system, similar to that of a bat, enables the dolphin to navigate among its companions and larger objects and to detect fish, squid, and even small shrimp. The whistles are single-toned squeals that come from deeper in the larynx. They are used to communicate alarm, sexual excitement, and perhaps other emotional states. Because of the ability of dolphins to learn and perform complex tasks in captivity, their continuous communications with one another, and their ability, through training, to approximate the sounds of a few human words, some investigators have suggested that the animals might be capable of learning a true language and communicating with humans. Most authorities, however, agree that although the dolphin's problem-solving abilities put the animal on an intelligence level close to that of primates, no evidence exists that dolphin communications approach the complexity of a true language. The name dolphin is also applied to food fish of a different genus that have long, continuous dorsal fins. The fish, found worldwide in tropical marine waters, can reach a length of 1.5 m (5 ft). Scientific classification: Dolphins belong to the suborder Odontoceti of the order Cetacea. The bottle-nosed dolphin is classified as Tursiops truncatus, the common dolphin as Delphinus delphis, and the tucuxi dolphin as Sotalia fluviatilis. The killer whale is classified as Orcinus orca. Pilot whales make up the genus Globicephala. The white-sided dolphin is classified as Lagenorhynchus obliquidens.