Whale
2007 Schools Wikipedia Selection. Related subjects: Mammals
The term whale is ambiguous: it can refer to all cetaceans, to just the larger ones, or only to members of particular families within the order Cetacea. The last definition is the one followed here. 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.
Origins and taxonomy
All whales, 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 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 species of 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.
A complete up-to-date taxonomical listing of all cetacean species, including all whales, is maintained at the Cetacea article.
Anatomy
Like all mammals, whales breathe air into lungs, are warm-blooded, feed their young milk from mammary glands, and have some (although very little) hair. A young scientist, Eric Alexander Ivanov, in 1911, was the first to discover that the whale's ancestors lived on land, and that whales have adapted to a fully aquatic life. At first his findings were not accepted by the scientific community, but were later proved correct. Ivanov worked with others to stop whaling in the United States. Eric Ivanov died shortly after his goal was achieved.
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 mammal that has ever lived, and the largest living animal, at up to 30 m (93ft) long and 180 tons.
Their skin has evolved hydrophilic properties. Its surface is covered with microscopic pores surrounded by nanoridges. Between these ridges there is a rubber-like gel which is excreted from the gaps between the skin cells. This gel contains enzymes that attack microbes, and the edge of the ridges makes it hard for smaller organisms to get attached.
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.
Anatomy of the ear
While there are direct similarities between the ears of whales and humans, whales’ ears have specific adaptations to their underwater environment. In humans, the middle ear works as an impedance matcher between the outside air’s low-impedance and the cochlear fluid’s high-impedance. In aquatic mammals like whales, however, there is no great difference between the outer and inner environments. Instead of sound passing through outer ear to middle ear, whales receive sound through their lower jaw, where it passes through a low-impedance, fat-filled cavity.
Behaviour
Whales are widely 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 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.
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.
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.
Intelligence
A once traditional but now discredited indicator of intelligence is overall brain size, 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. A slightly better indicator is the brain-body ratio: the size of the brain compared to body mass. Here humans have a decisive advantage. A human brain comprises about 2% of the human body mass, while the sperm whale's brain comprises only 0.02% of its body mass. A cow's brain is four times as large as a whale's on this measurement. On the other hand, a large proportion of a whale's body mass is blubber, which requires no brain power, and this distorts the ratio somewhat. However, because cetacean brains function quite differently from the human brain, even if whales had matching body/brain weight ratio to humans, it is not a conclusive indication of high intelligence. Simply, "overall" brain size is not a decisive criterion because it is now known that different parts of the brain regulate different functions, mostly physiological. Hummingbirds have an even higher brain-to-body ratio than humans. The next consideration is the structure of the brain. It is generally agreed that the growth of the neocortex, both absolutely and relative to the rest of the brain, during human evolution, has been responsible for the evolution of intelligence, however defined. In most mammals the neocortex has six layers, and its different functional areas (vision, hearing, etc) are sharply differentiated. The whale neocortex, on the other hand, has only five layers, and there is little differentiation of these layers according to function. This has led some to argue that the whale brain has not significantly evolved since the distant ancestors of the whale took to a marine lifestyle about 50 million years ago.
Many people, particularly in the West, believe that cetaceans in general, and whales in particular, are highly intelligent animals. This belief has become one of a central argument against whaling (killing whales for food or other commercial reasons). Proponents of whale and dolphin intelligence cite the social behaviour of whales and their apparent capacity for communication as evidence of a sophisticated intellect, though scientists often carefully point out the difference between the social traits and intelligence of animals, which laymen often confuse. 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.
The particular dispute in case of cetaceans is the conflict between social ability and abstract problem solving ability. Cetaceans, particularly dolphins, are highly social, and in addition they are generally friendly to humans. Some tests even indicate that they may even be social to the point of being self-aware. This has been the primary cause of perception among the public that cetaceans can be considered to be highly intelligent. However, canines and many other pack animals are also social (and are often perceived by the public to be intelligent due to such behaviour) but their problem solving abilities are usually rated lower than those of pigs. Dolphins also do poorly in (abstract) problem solving, which is considered a more rigorous indication of intelligence. Another misconception common amongst the public is to jump to the conclusion that if dolphins are intelligent, then that must mean that other cetaceans are intelligent: or, for that matter, if dolphins are not intelligent, then other cetaceans are not intelligent.
"Into the Brains of Whales" by Mark Peter Simmonds was published in the Journal of Applied Animal Behaviour Science 100 (2006) 103-116. In this article it is asserted that behavior and social structures are accurate indicators of intelligence. On this premise, the author argue that that whales and dolphins are highly intelligent though most of his argument is based on dolphins, as it is impossible or too costly to conduct experiment or observation on whales. One indicator of intelligence, it is argued, is self-awareness. It is argued, though the finding is still disputed, that Bottlenose dolphins have been shown to be able to recognize themselves in a mirror. This behaviour had previously only been recorded in humans, elephant and apes. Also, the use of tools is another example of intelligence. An example of this form of intelligence has been observed in Indo-Pacific bottlenose dolphins who carry sponges on their beaks to protect themselves when foraging for food. Further evidence of "intelligence", as defined by Simmonds are emotions typically seen in humans such as grief, parental love and joy, though these are fairly common trait of many mammals especially pack animals. Another example of intelligence are complex social interactions and structures. These traits are seen in dolphins and whales. An example being that whales were observed to have a cohesion and reliance upon each other and that despite risk of dehydration, being stranded and risking shark attack, a group of false killer whales floated for 3 days in the shallows of the straits of Florida, USA to protect an injured male from shark attack. The whales became agitated when attempts by rescuers were made to separate them. The whales only calmed when reunited.
On the other hand, another, and some argue to be more rigorus, definition of intelligience is "the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience." In the case of dolphins, some assert that they do poorly in this respect. In a paper published in Biological Reviews of the Cambridge Philosophical Society, Paul Manger argue that the size of cecetarian brain is the evolutionary result of need to keep brain warm. Further Manger stated that, "You put an animal in a box, even a lab rat or gerbil, and the first thing it wants to do is climb out of it. If you don't put a lid on top of the bowl a goldfish it will eventually jump out to enlarge the environment it is living in,... But a dolphin will never do that. In the marine parks, the dividers to keep the dolphins apart are only a foot or two above the water between the different pools."
From an evolutionary point of view, this is consistent with the principles of natural selection. Intelligence does not arise spontaneously: like any other animal capacity, it evolves under the pressure of the animal's environment. The human brain has evolved under the pressure of natural selection in a hostile terrestrial environment. The key primate characteristics - bipedalism and the opposable thumb - gave the early hominids the ability to manipulate their environment through the use of technology (by making tools). This unique adaptation created a virtuous cycle: more intelligence and consequent tool-making gave hominids with a decisive evolutionary advantage, leading to larger and more sophisticated brains functions, and thus to more tool-making. This process is one of the proposed explanations of the exponential growth of hominid intelligence over the past million years.
By contrast, the whale has faced no such environmental stimuli to brain evolution. Whales live in an unchanging and benign environment with few natural predators. Their sole adaptation to their marine environment has been increasing size. The whale's lifestyle consists of swimming and eating, tasks which fish perform perfectly competently with very small brains in relative term. From an evolutionary point of view, there is no reason for whales to have evolved intelligence, since their survival does not require them to perform any tasks for which intelligence is necessary.
Some whale species have a sophisticated social system. It is suggested that they can recognise and differentiate each individual whale. Many other animals, including insects, have complex social systems, and many others, such as birds, have sophisticated communications. Whales also have very acute hearing with well developed section of brain which govern this function, which gives them advanced echo-location capacities analogous to sonar - but so do bats. All this has led a number of, though far from all, zoologists to a conclusion that there is no convincing evidence for whale intelligence. A better understanding of whale communications and whale behaviour may solve this problem eventually.
Whales and humans
Some species of large whales are endangered as a result of large-scale whaling during the nineteenth and twentieth centuries. 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 an open-ended moratorium on all commercial whaling in 1986. 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 would drown 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 an estimated 96% 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.
Environmentalists have long argued that some cetaceans, including whales, are endangered by sonar used by advanced navies. In 2003 British and Spanish scientists suggested in Nature that sonar is connected to whale beachings and to signs that the beached whales have experienced decompression sickness. Mass whale beachings occur in many species, mostly beaked whales that use echolocation systems for deep diving). The frequency and size of beachings around the world, recorded over the last 1,000 years in religious tracts and more recently in scientific surveys, has been used to estimate the changing population size of various whale species by assuming that the proportion of the total whale population beaching in any one year is constant.
Despite the concerns raised about sonar which may invalidate this assumption, this population estimate technique is still popular today. Researchers in the area ( Talpalar & Grossman, 2005) support the view 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 has been ordered by the U.S. judiciary 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.
Conservationists are concerned that seismic testing used for oil and gas exploration may also damage the hearing and echolocation capabilities of whales. They also suggest that disturbances in magnetic fields caused by the testing may also be responsible for beaching.
Some scientists and environmentalists suggest that some whale species are also endangered due to a number of other human activities such as the unregulated use of fishing gear, that often catch anything that swims into them, whales collisions with ships, toxins and the combination of toxins POPs among other threats.
Whales in culture
- A kenning in Beowulf refers to the sea as the "whale-road".
- Procopius mentions a whale, nicknamed Porphyrio by the Byzantines, who depleted fisheries in the Sea of Marmara.
- The King James Version of the Bible mentions whales four times: "And God created great whales" ( Genesis 1:21); "Am I a sea, or a whale, that thou settest a watch over me? ( Job 7:12); "Thou art like a young lion of the nations, and thou art as a whale in the seas ( Ezekiel 32:2); and "For as Jonas [sic] was three days and three nights in the whale's belly; so shall the Son of man be three days and three nights in the heart of the earth" ( Matthew 12:40).
- Nevertheless, the passages in question do not unambiguously refer to whales; modern translations tend to use other terms; for example the New International Version uses "creatures of the sea"; "monster of the deep"; "monster"; and "huge fish" respectively.
- The story of Jonah being swallowed by a whale is mentioned in the Qur'an as well.
- A whaling voyage is the plot of Herman Melville's novel Moby-Dick. In the book, Melville classed whales as "a spouting fish with a horizontal tail", this despite science suggesting otherwise the previous century. (His narrator acknowledged "the grounds upon which Linnaeus would fain have banished the whales from the waters" but writes that when he presented them to "my friends Simeon Macey and Charley Coffin, of Nantucket ... they united in the opinion that the reasons set forth were altogether insufficient. Charley profanely hinted they were humbug" (Chapter 32).) Melville's book is a classic of American literature: part adventure novel, part metaphysical allegory, and part natural history; it is essentially a summary of 19th century knowledge about the biology, ecology and cultural significance of the whale.
- Some cultures associate some level of divinity with the whale, such as in some places in Ghana and the Vietnamese, who occasionally hold funerals for beached whales, a throwback to Vietnam's ancient sea-based Austro-asiatic culture.
- Festivals celebrating whales have sprung in both Sitka and Kodiak Alaska. They feature speakers on marine biology and celebrate the creatures with art, music, whale watching cruises, and symposiums.