There are about 80 species of cetaceans, a classification that included whales, dolphins and porpoises. Among these 80 species, there are 32 species of whales. The study of fossils indicates that the ancestors of today's whales gradually returned from land to live in the sea. All are air-breathing, warm blooded mammals that bear live young and nurse their young on milk. The young are cared for until they can look after themselves. Among the largest animals on earth, whales range in size from five to 100 feet in length, and fall into two categories: toothed (odontoceti) and baleen (mysticeti). Cetaceans play an important role in the life of the ocean. As such, they serve as flagships for the health and well being of the whole marine ecosystem.
Baleen Whales: Most whales are toothed. The Mysticeti or "baleen or whalebone whales", often called "moustached", are named after their feeding apparatus; a series of transverse plates of comb-like baleen (made of similar material to that of the human fingernail) which descend from the roof of the mouth and serve to strain plankton and small fish. They are made of hard but flexible material rooted in the animal's upper jaw. Water sieves through and the baleen catches and holds the whale's food: small fish and especially krill, shrimp-like crustaceans found in the Arctic and Antarctic oceans. Baleens are further subdivided into skimmers (swimming open-mouthed close to the ocean surface, straining food directly through the baleen) and gulpers (which swallow enormous quantities of water, force the water back out of the mouth to trap plankton against the inside surface of the baleen). Other distinctive characteristics of the baleen whales include a symmetrical skull with no melon (the apparatus used by odontocetes for echolocation) and a pair of nasal cavities. Baleen species include the humpback, blue (largest of all whales one measured 113.5 feet and weighed approximately 170 tons), bowhead, Bryde's, Cuvier's beaked, minke, pygmy (smallest baleen), right, fin (second largest whale), grey and sei. All baleen whales and the sperm whale are commonly referred to as "great whales".
Toothed Whales: The Odontoceti or "toothed whales" have either no, few, or numerous uniform and conical teeth, asymmetrical skull and single nasal passage. Toothed whales, generally smaller than baleens, are predators. They employ a camouflage called counter shading (darker colored on top, lighter colored beneath) to hunt food undetected. The light coloration conceals them from sight by blending in with the sunlit water from below. From above, the upper, darker colors diminish their outline by the sun striking the water from above. Toothed whales often hunt in groups, rounding up and corralling prey. Killer whales in a group can successfully hunt polar bears and baleens much larger than themselves. Toothed species include: Baird's beaked, bottle-nosed, false killer, killer, narwhal, pilot, pygmy sperm, rough-toothed, sperm (largest toothed whale; "Moby Dick" was a sperm whale), and the beluga or white whale. This category also includes dolphins and porpoises.
Physical Characteristics: The fossil history of the cetaceans is incomplete and controversial. In general it seems that they evolved from small, primitive, land mammals which may have returned to the water some 70-90 million years ago. Today, they have evolved into hairless, aquatic animals, who still breathe with lungs rather than gills, and nurse their young.
Completely adapted to life in the water, whales breathe through one or two blowholes (whale's "nostrils") on top of the head, which allows them to breathe without interrupting swimming. The whale's powerful forward movement is accomplished by an up-and-down, semi-rotary, "sculling" movement of the tail, as opposed to the side-to-side movement fish employ. The whale's flukes or tail fins are horizontal in the water and it uses its flippers to steer. Some whales swim in very cold water, adapted for it by the thick coat of fat (blubber) around their bodies. Blubber stores energy, contributes to a whale's stream lined form and, particularly in smaller whales, is important insulation in cold water. Of all the whales, the sperm is the champion breath-holder among mammals. It is known to descend to depths of a mile or more and is able to hold its breath for more than two hours. Their bodies are streamlined: reproductive organs, mammary glands, and ears are all internal. Their strong tails end in horizontal flukes, and what were once front legs are now flippers. The largest whale, the blue, can be 100 feet long and can weigh as much as 32 elephants or 2,267 150-pound human beings.
Diet and Hunting: It is something of a paradox that the world's largest creatures feed on some of the world's smallest. For instance, the enormous blue whale feeds on plankton, the largest of which -- krill, tiny shrimp -- are no more than two inches long; the adult blue whale can consume 9,000 pounds of food per day. Whales hunt by sound, rather than sight, using a sonar technique called "echo-location." They send out a series of clicks which bounce back when the sound waves encounter solid objects. The sonar gives the whale direction, distance, shape and composition of an object. This sonar not only helps them hunt, but navigate.
The sounds they emit can travel as far as 2,000 miles from a "sending" whale and be heard by a "receiving" whale. It is how species communicate with each other and learn the "songs" they sing. However, this sophisticated navigation system can fail them for some unknown reason and whales sometimes strand themselves up on beaches. Sometimes a whole herd becomes confused and they strand themselves as a group.
Reproduction & Development: Many whales spend six months in colder waters, rich in plankton, but travel to more tropical seas to breed and bear their young -- in order that the calves can swim in warmer water until they develop their blubber insulation. Female blue whales bear one calf every other year. Born under water, the calf can weigh some 23 pounds at birth, nurses for seven months, growing very fast -- a blue whale calf can increase its weight at the rate of 10 pounds per hour. Being mammals and air breathers, the babies do not breathe at all during the birth process. Their first act is to swim to the ocean surface to breathe; sometimes the mother swims beneath a weak calf to help it to the surface. The larger whales reach sexual maturity in four or five years and keep growing until they are about 12.
It is believed blue whales live about 50 years.
Northern Right Whale
Total Remaining: less than l,000
This is the most endangered of the large whales with no evidence of recovery. The most serious threats are vessel collisions and entanglement in fishing gear.
Southern Right Whale
Total Remaining: 1,500-4,000
This whale was heavily depleted by commercial whaling, but at least two populations (with nursery areas off Argentina and South Africa) are beginning to recover at an encouraging rate. The most serious threats to this whales survival is entanglement in fishing nets, habitat destruction such as oil and gas exploitation and illegal hunting.
These whales come close inshore to mate and to have their calves during the winter and spring months, but have been sighted during the summer months as well. Gestation is approximately one year, and calves are suckled for nine months to twelve months. Females breed about once every three years, or less frequently. Scientists identify individual whales by the distinctive white callosities (wart-like outgrowths of the skin that are covered with parasites) on the head. The whale has twin blowholes on the top of its head which expel air under great pressure. This condenses and forms a distinctive V-shape about 4 m high. Whalers called it the right whale because it was the 'right' whale to kill -it moved slowly, hugging the shoreline, provided a lot of oil, and floated when dead. Fewer than 100 of these whales survived off the South African coast when it was protected in 1940. Subsequently this number has increased to over 1,000 - one of the world's most important whale conservation success stories.
Total Remaining: 5,000
The blue whale is scattered throughout all the world's oceans, but the northern and Southern Hemisphere populations do not mix as they migrate to tropical waters from their polar feeding grounds at different times of the year. The NE Pacific population may be beginning to recover, but the Southern Hemisphere population shows no recovery at all. The most serious threat to this species is illegal hunting.
This is the largest living animal on earth and weighs up to 130 000 kg, or as much as 30 elephants or 1,600 people and can be as long as 33m, or the length of three railway carriages. It can grow up to 30 m in length. A favorite target of the 20th century whaling fleets, the blue whale was nearly exterminated before it was given world- wide protection in 1967. It is estimated that whaling has reduced the total world population to less than 10 000, from a pre-whaling figure of 300,000. Relentlessly pursued by 20th-century whaling fleets, the blue whale was nearly exterminated before receiving worldwide protection in 1967.
Total Remaining: 20,000
Humpback whales were seriously depleted by commercial whaling, but some populations seem to be starting to recover. Because they feed and breed near coasts they are vulnerable to human disturbance. Named for the distinctive hump behind the dorsal fin, this is an agile and acrobatic whale. It often leaps out of the water (called breaching) and slaps its tail and flippers on the water's surface. The most amazing characteristic of the humpback is its song - a fascinating pattern of grunts, squeals, squeaks, moans and hums in repeated sequences that may go on for 30 minutes or more. Experts think the singing may be part of the mating process. This species has been protected worldwide since 1963, and is now showing signs of recovery in South African waters.
Total Remaining: 2,000
Of the original three populations, one is extinct in the N. Atlantic, one is endangered in the western N. Pacific, and one has recovered from very low levels in the eastern N. Pacific. The main threats to this whale is that as shallow water feeders, they stay close to coasts and are vulnerable to human disturbance and entanglement in fishing nets. Their breeding grounds in the lagoon system of Baja, California are threatened by the expansion of onshore salt-extraction plants.
Status: Insufficiently known
Total Remaining: 2,000,000
There is more uncertainty over the remaining numbers of sperm whales than there is over the other great whales. This is because they remain under water for long periods, and because they are often found in large groups which makes information from surveys impossible to analyze in the same way as for the other whales. Research has now begun into acoustic survey techniques, but much more remains to be done. The whalers mostly targeted the larger males, so the balance between the sexes has been badly distorted. One of the best known of the worlds whales as it featured in Herman Melville's book Moby Dick. It is easily recognized by its huge head and row of large white teeth in the lower jaw. Although the sperm whale was heavily hunted in the 18th, 19th, and 20th centuries, it is now protected. Recognized by its massive head and large white teeth, the sperm whale is the only great whale that has one blowhole instead of two. Sperm whales dive deeper than any other whale more than 1,000m and find much of their food near the ocean floor.
The head of the sperm whale contains a huge amount of very fine, clear oil (called spermaceti). The sperm whale hunts with a sonar-like system called "echolocation". They produce sounds that bounce off prey and return to guide the listening whale
Threats: Whales have been hunted by people for at least 4 000 years. In more recent times, the advent of commercial whaling in the open seas (in the 1700s and 1 800s) and the development of the explosive cannon (1868) has resulted in a plundering of the world's whale stocks. Commercial whalers have hunted most great whale species, bringing many populations close to extinction. Whale oil and other products were once of enormous value, but now natural and synthetic substitutes are available for all of them. In spite of this, some whaling continues.