Like other mammals, whales breathe air, are warm-blooded, and produce milk to feed their young. Their adaptations for aquatic life include a streamlined form, nearly hairless skin, and an insulating layer of blubber, which can be as thick as 28 in. (70 cm) in some Arctic species. The forelimbs of whales are modified into flippers, and the hind legs are reduced to internal vestiges. Many species possess a dorsal fin. The tail is flattened into horizontal flukes and is used for propulsion. The head is very large, with a wide mouth and no external neck.
Whales have one or two nostril openings, called blowholes, located far back on the top of the head; the nostril valves close and the lungs compress when the whale dives. Most whales must surface every 3 to 20 min to breathe, but some, like the sperm whale, can remain submerged for more than an hour. Spouting occurs when the whale surfaces and clears water from its blowhole along with any moisture trapped in its air passages. The shape of the spout is characteristic of each type of large whale. Whales have small eyes, designed to withstand great pressures, and most species have good vision. Their hearing is also excellent. Many cetaceans have highly convoluted brains larger than those of humans, and whales are believed to be extremely intelligent.
Most large whales travel in small schools, or pods, but some, like the fin whale, swim alone or in pairs; small cetaceans form schools of up to several thousand individuals. Most large whales are found in open ocean, where they migrate thousands of miles between feeding and breeding grounds. Dolphins frequently live in coastal waters. A few dolphin species are found in tropical rivers. Females of most species give birth to a single calf every two to three years. Gestation periods range from 9.5 to 17 months. The newborn calf is pushed to the surface by the mother or by another adult; it is able to swim almost immediately and is nursed for 6 to 12 months. Some large whales are believed to have lived 100 years or more in the wild.
There are two major groups of whales—the toothed whales (suborder Odontoceti) and the toothless baleen whales (suborder Mysticeti).Toothed Whales
Toothed whales include two families that are widely distributed, the beaked and bottlenose whales (family Ziphiidae) and the sperm whale, or cachalot (family Physeteridae; DNA studies suggest, however, that it is more closely related to baleen whales); the beluga, or white whale, and the narwhal (family Monodontidae), small polar whales with no dorsal fin and only a few teeth; the river dolphins (family Platanispidae), which inhabit muddy rivers of India and South America; and several families better known as ocean dolphins and porpoises. The killer whale and pilot whale are types of dolphin. The white whale Moby-Dick, of Herman Melville's novel, was not a beluga but a sperm whale with prominent white features.
Toothed whales range in length from 4 to 60 ft (1.3-18.5 m). They catch fast-moving prey, like fish or squid. Many species use echolocation (sonar) for underwater navigation and hunting. They have a single blowhole and a wide throat to accommodate large prey. Some of the larger ones, like the sperm whale, can dive as deep as 1 mi (1.6 km).Toothless Whales
There are three families of baleen whales: the right whale family (Balaenidae), including the bowhead, or Greenland whale; the gray whale family (Eschrichtidae), with a single species (Eschrichtius robustus) found in the N Pacific Ocean; and the rorqual family (Balaenopteridae). Rorquals, the most familiar of the large whales, have large, pouchlike throats with furrows running from mouth to belly. The family includes the humpback whale, the sei whale, the minke whale, the Bryde's whale, the fin whale (or common rorqual), and the blue whale, which can grow to a length of 100 ft (30 m) and a weight of 150 tons.
Baleen whales are large species, usually over 33 ft (10 m) long. They are filter feeders, living on shrimplike krill, plankton, and small fish. They lack teeth but have brushlike sheets of a horny material called baleen, or whalebone, edging the roof of the mouth. With these strainers and their enormous tongues, tons of food can be separated from seawater. Baleen whales have narrow throats and paired blowholes. Male humpbacks produce a repeated pattern of sounds called a song during the mating season; the purpose is not clear, as all males in a group sing basically the same song.
All species of large whales have been drastically reduced in numbers by centuries of intensive whaling. An indefinite ban by the International Whaling Commission on commercial whaling of all large whales gradually went into effect following the 1984-85 season, and large portions of ocean have been designated whale sanctuaries. With these and various other protective efforts, some species have begun to return to acceptable numbers, but others, especially the right and blue whales, are still rare and endangered. After decades of protection the number of E Pacific gray whales seems to have returned to its estimated prewhaling level. Only the small minke whale exists in populations great enough for sustainable whaling to be considered. Whale products include whale oil, sperm oil, spermaceti, ambergris, and whalebone, as well as meat, bone meal, and liver oil. Natural and synthetic materials have replaced all whale products in the United States. See separate entry on whaling for more information.
Whales are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Cetacea.
See R. Ellis, The Book of Whales (1980) and Dolphins and Porpoises (1989); L. Watson, Sea Guide to Whales of the World (1981).
Whales are marine mammals which are neither dolphins (i.e. members of the families Delphinidae or Platanistoidae) nor porpoises. Orcas (Killer Whales) and Pilot whales have "whale" in their name, though they are dolphins for the purpose of classification.
All cetaceans, including whales, dolphins and porpoises, are descendants of land-living mammals of the Artiodactyl order (even-toed ungulate animals). Both cetaceans and artiodactyl are now classified under the super-order Cetartiodactyla which includes both whales and hippopotamuses. In fact, whales are the closest living relatives of hippopotamuses; they evolved from a common ancestor at around 54 million years ago. Whales entered the water roughly 50 million years ago. Cetaceans are divided into two suborders:
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,so called 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. They have a pelvis bone, which is a vestigial structure Whales breathe through their 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 mammal that has ever lived, and the largest living animal, at up to 35 m (105ft) long and 150 tons. Whales generally live for 40-90 years, depending on their species, and on rare occasions can be found to live over a century. Recently a fragment of a lance used by commercial whalers in the 19th century has been found in a bowhead whale caught off Alaska, which showed the whale to be between 115 and 130 years old. Furthermore, a technique for dating age from aspartic acid racemization in the whale eye, combined with a harpoon fragment, indicates an age of 211 years for one male, making bowhead whales the longest lived extant mammal species. Whale flukes often can be used as identifying markings, as is the case for humpback whales. This is the method by which the publicized errant Humphrey the whale was identified in three separate sightings.
A toothed whale, like the sperm whale, possess teeth with cementum cells overlying dentine cells. Unlike human teeth which are comprised mostly of enamel on the tooth portion outside of the gum, whale teeth have cementum outside the gum. Only in larger whales does some enamel show where the cementum has been worn away on the tip of the tooth revealing the underlying enamel.
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. This is thought because whales often sleep with only one eye closed.
Whales also communicate with each other using lyrical sounds, called whale song. Being so large and powerful, these sounds are also extremely loud (depending on the species); sperm whales have only been heard making clicks, as all toothed whales (Odontoceti) use echolocation and can be heard for many miles. They have been known to generate about 20,000 acoustic watts of sound at 163 decibels.
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 mode of reproduction spawns few offspring, but provides each with a high probability of survival in the wild.
The male genitals 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 newborn are delivered tail-first, minimising the risk of drowning. Whale cows nurse by actively squirting milk the consistency of toothpaste into the mouths of their young preventing loss to the surrounding aquatic environment.
Some species of large whales are endangered as a result of commercial whaling from the eleventh century to the twentieth. For centuries large whales have been hunted for oil, meat, baleen and ambergris (a perfume ingredient from the intestine of sperm whales). By the middle of the 20th century, whaling left many populations severely depleted.
The International Whaling Commission introduced a six year moratorium on all commercial whaling in 1986, which has been extended to the present day. For various reasons some exceptions to this moratorium exist; current whaling nations are Norway, Iceland and Japan and the aboriginal communities of Siberia, Alaska and northern Canada. For details, see whaling.
Several species of small whales are caught as bycatch in fisheries for other species. In the tuna fishery in the Eastern Tropical Pacific thousands of dolphins were drowned in purse-seine nets, until measures to prevent this were introduced. Fishing gear and deployment modifications, and eco-labelling (dolphin-safe or dolphin-friendly brands of canned tuna), have contributed to a reduction in the mortality of dolphins by tuna fishing vessels in recent years. In many countries, small whales are still hunted for food, oil, meat or bait.
Despite the concerns raised about sonar which may invalidate this assumption, this population estimate technique is still popular today. Talpalar and Grossman argue that it is the combination of the high pressure environment of deep-diving with the disturbing effect of the sonar which causes decompression sickness and stranding of whales. Thus, an exaggerated startle response occurring during deep diving may alter orientation cues and produce rapid ascent.
Following public concern, the U.S. Defense department was ordered by the US circuit court in California to strictly limit use of its Low Frequency Active Sonar during peacetime. Attempts by the UK-based Whale and Dolphin Conservation Society to obtain a public inquiry into the possible dangers of the Royal Navy's equivalent (the "2087" sonar launched in December 2004) have so far failed. The European Parliament on the other hand has requested that EU members refrain from using the powerful sonar system until an environmental impact study has been carried out.
Other human activities have been suggested to adversely impact whale populations, ranging from the unregulated use of fishing gear which catches anything that swims into it, to collisions with ships. Environmental toxins and the combination of toxins, particularly POPs (which concentrate up the food chain), have been shown to cause hearing loss by inhibiting the function of outer hair cells in the cochlea of the ear, and exposure to these toxins might affect whale echolocation, leading to beaching .
Whales are also threatened by climate change and global warming. As the Antarctic Ocean warms, krill populations, that are the main food source of some species of whales, reduce dramatically, being replaced by jelly like salps.
Whales are frequently portrayed in literature as violent creatures who attack shipping and kill or eat sailors, despite overwhelming scientific evidence to the contrary. This is especially true in literature written prior to the modern scientific study of the creatures, or in period literature. A common whale-themed plot device concerns mariners who are swallowed whole by a whale, and find themselves trapped alive in the creature's belly. In some instances, the victims of these encounters are able to escape, often by causing the whale sufficient gastronomic distress that it is forced to expel them; in other such occurrences in fiction, the victim is doomed.
Portrayals of whales or whaling in literature, film, TV, or religion include: