WHAT ARE WHALES?

According to modern terminology, whales are the larger members of the order Cetacea. This order of aquatic mammals is divided into three suborders: the Mysticeti, the baleen whales; the Odontoceti, the toothed whales; and the Archaeoceti, an extinct group known only through fossils. The toothed whales (Odontoceti) also include the smaller DOLPHIN and PORPOISE.

The large baleen whales comprise three families and about a dozen species. All these species lack teeth except as vestiges in the embryos. Instead, they possess a row of fringed plates of baleen (whalebone), which is a keratinaceous (horny) material developed from the gums. The fringed plates of baleen act as a filter, or sieve, straining small marine organisms from the water. The baleen whales are primarily plankton feeders and derive most of their nourishment from marine organisms that may be only a few millimeters (several hundredths of an inch) in length. Their principal food in the polar regions, especially in the Antarctic, consists of small, shrimplike crustaceans collectively known as "krill." Commonly known baleen whales include the right whales, Balaena; the gray whale, Eschrichtius gibbosus; the blue whale, Balaenoptera musculus; the fin whale, B. physalus; and the humpback whale, Megaptera novaeanglia. The largest species, and the largest animal that has ever lived, is the blue whale. Specimens up to 30 m (100 ft) in length have been recorded, with weights estimated at more than 118 metric tons.

The toothed whales are all predators, feeding actively on fish and squid, and they possess sharp teeth, usually in both jaws, used to catch their prey. The odontocetes that are commonly called whales comprise five families and about 30 species, including such forms as pilot whales, Globicephala; beaked whales, Mesoplodon; the beluga or white whale, Delphinapterus leucas; the killer whale, Orcinus orca; the pygmy sperm whale, Kogia; and the species best known through Melville's novel Moby-Dick, the sperm whale, Physeter catodon. Sperm whales have been recorded up to 19 m (62 ft) in length, and this species is recognizable by the large, oblong head and the relatively tiny, narrow lower jaw.Whales are the largest species of exclusively aquatic mammals, members of the order Cetacea, which also includes dolphins and porpoises. They include the largest known animals ever evolved

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The term whale is ambiguous as it refers to all cetaceans, not just the larger ones, or only to members of particular families within the order Cetacea. Whales are those cetaceans which are neither dolphins (i.e. members of the families Delphinidae or Platanistoidea) nor porpoises. This can lead to some confusion because Orcas ("Killer Whales") and Pilot Whales have "whale" in their name, but they are dolphins for the purpose of classification.

Whales, along with most dolphins and porpoises, are descendants of land-living mammals, most likely of the Artiodactyl order. They entered the water roughly 50 million years ago.

Cetaceans are divided into two suborders:

The baleen whales are characterized by the baleen, a sieve-like structure in the upper jaw made of keratin, which they use to filter plankton from the water. They are the largest whale. The toothed whales have teeth and prey on fish, squid, or both. An outstanding ability of this group is to sense their surrounding environment through echolocation.

Like all mammals, whales breathe air into lungs, are warm-blooded, breast-feed their young, and have some (although very little) hair. The whales' ancestors lived on land, and their adaptions to a fully aquatic life are quite striking. The body is fusiform, resembling the streamlined form of a fish. The forelimbs, also called flippers, are paddle-shaped. The end of the tail holds the fluke, or tail fins, which provide propulsion by vertical movement. Although whales generally do not possess hind limbs, some whales (such as sperm whales and baleen whales) sometimes have rudimentary hind limbs; some even with feet and digits. Most species of whale bear a fin on their backs known as a dorsal fin.

Beneath the skin lies a layer of fat, the blubber. It serves as an energy reservoir and also as insulation. Whales have a four-chambered heart. The neck vertebrae are fused in most whales, which provides stability during swimming at the expense of flexibility.

 

 

 

Whales breathe through blowholes, located on the top of the head so the animal can remain submerged. Baleen whales have two; toothed whales have one. The shapes of whales' spouts when exhaling after a dive, when seen from the right angle, differ between species. Whales have a unique respiratory system that lets them stay underwater for long periods of time without taking in oxygen. Some whales, such as the Sperm Whale, can stay underwater for up to two hours holding a single breath. The Blue Whale is the largest known animal that has ever lived, at up to 30 m (93ft) long and 180 tons.

Whales are broadly classed as predators, but their food ranges from microscopic plankton to very large fish. Males are called bulls; females, cows. The young are called calves.

Because of their environment (and unlike many animals), whales are conscious breathers: they decide when to breathe. All mammals sleep, including whales, but they cannot afford to fall into an unconscious state for too long, since they need to be conscious in order to breathe. It is thought that only one hemisphere of their brains sleeps at a time, so that whales are never completely asleep, but still get the rest they need. Whales are thought to sleep around 8 hours a day.

Whales also communicate with each other using beautiful lyrical sounds. Being so large and powerful these sounds are also extremely loud and can be heard for many miles. They have been known to generate about 20,000 acoustic watts of sound at 163 decibels. See Table of sound decibel levels.

Females give birth to a single calf. Nursing time is long (more than one year in many species), which is associated with a strong bond between mother and young. In most whales reproductive maturity occurs late, typically at seven to ten years. This strategy of reproduction spawns few offspring, but provides each with a high rate of survival

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The genital organs are retracted into cavities of the body during swimming, so as to be streamlined and reduce drag. Most whales do not maintain fixed partnerships during mating; in many species the females have several mates each season. At birth the newborn is delivered tail-first, so the risk of drowning is minimized. Whale mothers nurse the young by actively squirting the fatty milk into their mouths, a milk that according to German naturalist Dieffenbach, bears great similarities to cow's milk. Biologists compare the consistency of whale milk to cottage cheese; it must be thick, or else it will dissipate into the surrounding water.

Many people believe that cetaceans in general, and whales in particular, are highly intelligent animals. This belief has become a central argument against whaling (killing whales for food or other commercial reasons).

Many species of whales such as the Killer Whale (Orcinus Orca) travel in large pods and rely on each other's help to find food. For example, in the Arctic Ocean Orcas have been documented tipping small ice patches, so that a seal resting upon it can slide down into a waiting Orca's mouth. Group attacks and feeding are successful tactics and intelligence features used by whales.

There is no universally agreed definition of "intelligence." One commonly used definition is "the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience." Proponents of whale intelligence cite the social behavior of whales and their apparent capacity for language as evidence of a sophisticated intellect. Given the radically different environment of whales and humans, and the size of whales compared to dolphins or chimpanzees, for instance, it is extremely difficult to test these views experimentally.

One traditional indicator of intelligence is brain capacity, since humans have bigger brains than most other animals. Whales have the largest brain of any animal. A typical sperm whale brain weighs about 7.8 kg, whereas a typical human brain weighs about 1.5 kg. While it may seem that this would indicate that five times greater intelligence, in mammals brain size is in approximate ratio to body size, and most of the extra capacity is used to manage the larger body.

Whales have a sophisticated social system. Their communication system may contain some of the elements of true language, although our knowledge of whale communications is not very advanced. Many other animals, including insects, have complex social systems, and many others, such as birds, have sophisticated communications. Whales also have very acute hearing, which gives them advanced echo-location capacities analogous to sonar - but so do bats. All this has led many (though far from all) zoologists to the conclusion that there is no convincing evidence for whale intelligence. A better understanding of whale communications and whale behaviour may solve this problem eventually.