Editing Whale (section)

==Biology==
===Anatomy===
[[File:Baleen parts.png|thumb|right|Features of a [[blue whale]]]]
[[File:Sperm whale skeleton labelled.jpg|thumb|Features of a [[sperm whale]] skeleton]]
Whales have torpedo-shaped bodies with non-flexible necks, limbs modified into flippers, non-existent external ear flaps, a large tail fin, and flat heads (with the exception of [[Monodontidae|monodontids]] and [[Ziphiidae|ziphiids]]). Whale skulls have small eye orbits, long snouts (with the exception of monodontids and ziphiids) and eyes placed on the sides of its head. Whales range in size from the {{convert|2.6|m|ft|adj=on}} and {{convert|135|kg|lbs|adj=on}} dwarf sperm whale to the {{convert|34|m|ft|adj=on}} and {{convert|190|MT|ST|adj=on}} blue whale. Overall, they tend to dwarf other cetartiodactyls; the blue whale is the largest creature on Earth. Several species have female-biased sexual dimorphism, with the females being larger than the males. One exception is with the sperm whale, which has males larger than the females.{{sfn|Reidenberg|2012|pp=510–511}}{{sfn|Ralls|Mesnick|1984|pp=1005–1011}}

Odontocetes, such as the sperm whale, possess teeth with [[cementum]] cells overlying [[dentine]] cells. Unlike human teeth, which are composed mostly of [[Tooth enamel|enamel]] on the portion of the tooth outside of the gum, whale teeth have cementum outside the gum. Only in larger whales, where the cementum is worn away on the tip of the tooth, does enamel show. Mysticetes have large [[whalebone]], as opposed to teeth, made of keratin. Mysticetes have two blowholes, whereas Odontocetes contain only one.{{sfn|Reidenberg|2012|pp=509–510}}

Breathing involves expelling stale air from the [[blowhole (anatomy)|blowhole]], forming an upward, steamy spout, followed by inhaling fresh air into the lungs; a humpback whale's lungs can hold about {{convert|5,000|L|usgal}} of air. Spout shapes differ among species, which facilitates identification.{{sfn|Reidenberg|2012|pp=507–508}}{{sfn|Scholander|1940}}

All whales have a thick layer of [[blubber]]. In species that live near the poles, the blubber can be as thick as {{convert|11|in|cm}}. This blubber can help with buoyancy (which is helpful for a 100-ton whale), protection to some extent as predators would have a hard time getting through a thick layer of fat, and energy for fasting when migrating to the equator; the primary usage for blubber is insulation from the harsh climate. It can constitute as much as 50% of a whale's body weight. Calves are born with only a thin layer of blubber, but some species compensate for this with thick lanugos.{{sfn|Klinowska|1991|p=5}}{{sfn|Reidenberg|2012|p=510}}

Whales have a two- to three-chambered stomach that is similar in structure to those of terrestrial carnivores. Mysticetes contain a [[proventriculus]] as an extension of the [[oesophagus]]; this contains stones that grind up food. They also have [[Fundic stomach|fundic]] and [[Pyloric stomach|pyloric]] chambers.{{sfn|Stevens|Hume|1995|p=11}}

===Locomotion===<!-- [[Whale sounding]] links here -->
[[File:GreenlandWhaleLyd3.jpg|thumb|Skeleton of a [[bowhead whale]]; notice the vestigial [[pelvis]]. [[Richard Lydekker]], 1894]]
Whales have two flippers on the front, and a tail fin. These flippers contain four digits. Although whales do not possess fully developed hind limbs, some, such as the sperm whale and bowhead whale, possess discrete rudimentary appendages, which may contain feet and digits. Whales are fast swimmers in comparison to seals, which typically cruise at 5–15 kn, or {{convert|9|–|28|kph|mph}}; the fin whale, in comparison, can travel at speeds up to {{convert|47|kph|mph}} and the sperm whale can reach speeds of {{convert|35|kph|mph}}. The fusing of the neck vertebrae, while increasing stability when swimming at high speeds, decreases flexibility; whales are unable to turn their heads. When swimming, whales rely on their tail fin to propel them through the water. Flipper movement is continuous. Whales swim by moving their tail fin and lower body up and down, propelling themselves through vertical movement, while their flippers are mainly used for steering. Some species [[Cetacean surfacing behaviour|log]] out of the water, which may allow them to travel faster. Their skeletal anatomy allows them to be fast swimmers. Most species have a [[dorsal fin]].{{sfn|Reidenberg|2012|p=508}}{{sfn|Klinowska|1991|pp=122–262}}

Whales are adapted for diving to great depths. In addition to their streamlined bodies, they can slow their heart rate to conserve oxygen; blood is rerouted from tissue tolerant of water pressure to the heart and brain among other organs; [[haemoglobin]] and [[myoglobin]] store oxygen in body tissue; and they have twice the concentration of myoglobin than haemoglobin. Before going on long dives, many whales exhibit a behaviour known as sounding; they stay close to the surface for a series of short, shallow dives while building their oxygen reserves, and then make a sounding dive.{{sfn|Norena et al.|2000|pp=181–191}}

===Senses===
[[File:Delfinekko.gif|thumb|right|[[Biosonar]] by cetaceans]]
[[File:Sperm whale drawing with skeleton.jpg|thumb|right|Sperm whale skeleton. Richard Lydekker, 1894.]]

The whale ear has specific adaptations to the [[Ocean|marine]] environment. In humans, the [[middle ear]] works as an impedance equalizer between the outside air's low [[Acoustic impedance|impedance]] and the [[cochlea]]r fluid's high impedance. In whales, and other marine mammals, there is no great difference between the outer and inner environments. Instead of sound passing through the outer ear to the middle ear, whales receive sound through the throat, from which it passes through a low-impedance fat-filled cavity to the inner ear.{{sfn|Cranford et al.|2008}} The whale ear is acoustically isolated from the skull by air-filled sinus pockets, which allow for greater directional hearing underwater.{{sfn|Nummela et al.|2007|pp=716–733}} Odontocetes send out high-frequency clicks from an organ known as a [[melon (cetacean)|melon]]. This melon consists of fat, and the skull of any such creature containing a melon will have a large depression. The melon size varies between species, the bigger the more dependent they are on it. A beaked whale for example has a small bulge sitting on top of its skull, whereas a sperm whale's head is filled up mainly with the melon.{{sfn|Jeanette et al.|1990|pp=1–19}}{{sfn|Reidenberg|2012|p=512}}{{sfn|Thewissen|Perrin|Wirsig|2002|p={{page needed|date=April 2021}}}}{{sfn|Ketten|1992|pp=717–750}}

The whale eye is relatively small for its size, yet they do retain a good degree of eyesight. As well as this, the eyes of a whale are placed on the sides of its head, so their vision consists of two fields, rather than a binocular view like humans have. When belugas surface, their lens and cornea correct the nearsightedness that results from the refraction of light; they contain both [[rod cell|rod]] and [[cone cell|cone]] cells, meaning they can see in both dim and bright light, but they have far more rod cells than they do cone cells. Whales do, however, lack short wavelength sensitive visual pigments in their cone cells indicating a more limited capacity for colour vision than most mammals.{{sfn|Mass et al.|2007|pp=701–715}} Most whales have slightly flattened eyeballs, enlarged pupils (which shrink as they surface to prevent damage), slightly flattened corneas and a [[tapetum lucidum]]; these adaptations allow for large amounts of light to pass through the eye and, therefore, a very clear image of the surrounding area. They also have glands on the eyelids and [[corneal epithelium|outer corneal layer]] that act as protection for the cornea.{{sfn|Jeanette et al.|1990|pp=505–519}}{{sfn|Reidenberg|2012|p=512}}

The [[olfactory lobes]] are absent in toothed whales, suggesting that they have no sense of smell. Some whales, such as the [[bowhead whale]], possess a [[vomeronasal organ]], which does mean that they can "sniff out" krill.{{sfn|Jeanette et al.|1990|pp=481–505}}

Whales are not thought to have a good sense of taste, as their taste buds are atrophied or missing altogether. However, some toothed whales have preferences between different kinds of fish, indicating some sort of attachment to taste. The presence of the Jacobson's organ indicates that whales can smell food once inside their mouth, which might be similar to the sensation of taste.{{sfn|Jeanette et al.|1990|pp=447–455}}

===Communication===
{{Main|Whale vocalization}}
{{Listen|filename=Whales and Dolphins whale nature sounds songs nueva esparta.ogg|title=Humpback whale "song"|description=Recording of Humpback Whales singing and Clicking.|format=[[Ogg]]}}

Whale vocalization is likely to serve several purposes. Some species, such as the humpback whale, communicate using melodic sounds, known as [[whale sound|whale song]]. These sounds may be extremely loud, depending on the species. Humpback whales only have been heard making clicks, while toothed whales use [[biosonar|sonar]] that may generate up to 20,000 watts of sound (+73&nbsp;[[dBm]] or +43&nbsp;[[Decibel watt|dBw]]){{sfn|Whitehead|2003|p=4}} and be heard for many miles.

Captive whales have occasionally been known to mimic human speech. Scientists have suggested this indicates a strong desire on behalf of the whales to communicate with humans, as whales have a very different vocal mechanism, so imitating human speech likely takes considerable effort.{{sfn|Collins|2012}}

Whales emit two distinct kinds of acoustic signals, which are called whistles and clicks:{{sfn|Mann|2000|p=9}}
Clicks are quick broadband burst pulses, used for [[biosonar|sonar]], although some lower-frequency broadband vocalizations may serve a non-echolocative purpose such as communication; for example, the pulsed calls of belugas. Pulses in a click train are emitted at intervals of ≈35–50 [[millisecond]]s, and in general these inter-click intervals are slightly greater than the round-trip time of sound to the target.
Whistles are narrow-band [[frequency modulation|frequency modulated (FM)]] signals, used for communicative purposes, such as contact calls.

===Intelligence===
{{Main|Cetacean intelligence}}
{{See also|Cetacean surfacing behaviour}}

Whales are known to teach, learn, cooperate, scheme, and grieve.{{sfn|Siebert|2009}} The neocortex of many species of whale is home to elongated [[spindle neurons]] that, prior to 2007, were known only in hominids.{{sfn|Watson|2006|pp=1107–1112}} In humans, these cells are involved in social conduct, emotions, judgement, and theory of mind. Whale spindle neurons are found in areas of the brain that are homologous to where they are found in humans, suggesting that they perform a similar function.{{sfn|Hof|2007|pp=1–31}}

[[File:Whales Bubble Net Feeding-edit1.jpg|thumb|Bubble net feeding]]

[[Brain size]] was previously considered a major indicator of the intelligence of an animal. Since most of the brain is used for maintaining bodily functions, greater ratios of brain-to-body mass may increase the amount of brain mass available for more complex cognitive tasks. [[Allometric]] analysis indicates that mammalian brain size scales at approximately the {{frac|2|3}} or {{frac|3|4}} exponent of the body mass. Comparison of a particular animal's brain size with the expected brain size based on such allometric analysis provides an [[encephalization quotient|encephalisation quotient]] that can be used as another indication of animal intelligence. [[Sperm whale]]s have the largest brain mass of any animal on Earth, averaging {{convert|8000|cm3|in3}} and {{convert|7.8|kg|lbs}} in mature males, in comparison to the average human brain which averages {{convert|1450|cm3|in3}} in mature males.{{sfn|NOAA Fisheries|2013}} The [[brain-to-body mass ratio]] in some odontocetes, such as belugas and narwhals, is second only to humans.{{sfn|Mind Matters|2008}}

Small whales are known to engage in complex play behaviour, which includes such things as producing stable underwater [[toroid]]al air-core [[vortex]] rings or "[[bubble ring]]s". There are two main methods of bubble ring production: rapid puffing of a burst of air into the water and allowing it to rise to the surface, forming a ring, or swimming repeatedly in a circle and then stopping to inject air into the [[Helix|helical]] vortex currents thus formed. They also appear to enjoy biting the vortex-rings, so that they burst into many separate bubbles and then rise quickly to the surface.{{sfn|Deep Ocean}} Some believe this is a means of communication.{{sfn|Griffin|2015}} Whales are also known to produce bubble-nets for the purpose of foraging.{{sfn|Wiley et al.|2011|pp=575–602}}

Larger whales are also thought, to some degree, to engage in play. The [[southern right whale]], for example, elevates their tail fluke above the water, remaining in the same position for a considerable amount of time. This is known as "sailing". It appears to be a form of play and is most commonly seen off the coast of [[Argentina]] and [[South Africa]]. [[Humpback whale]]s, among others, are also known to display this behaviour.{{sfn|Leighton et al.|2007|pp=17–21}}

{{anchor|Reproduction}}

=== Life cycle ===
{{See also|Right whale#Courtship and reproduction}}

Whales are fully aquatic creatures, which means that birth and courtship behaviours are very different from terrestrial and semi-aquatic creatures. Since they are unable to go onto land to calve, they deliver the baby with the fetus positioned for tail-first delivery. This prevents the baby from drowning either upon or during delivery.

[[File:Southern right whale4.jpg|thumb|upright|A [[southern right whale]] tail-sailing]]
To feed the newborn, whales, being aquatic, must squirt the milk into the mouth of the calf. Nursing can occur while the mother whale is in the vertical or horizontal position. While nursing in the vertical position, a mother whale may sometimes rest with her tail flukes remaining stationary above the water. This position with the flukes above the water is known as "whale-tail-sailing." Not all whale-tail-sailing includes nursing of the young, as whales have also been observed tail-sailing while no calves were present.{{sfn|Higgs|2023}}

Being mammals, they have mammary glands used for nursing calves; weaning occurs at about 11 months of age. This milk contains high amounts of fat which is meant to hasten the development of blubber; it contains so much fat that it has the consistency of toothpaste.{{sfn|Modern Marvels|2007}} Like humans, female whales typically deliver a single offspring. Whales have a typical gestation period of 12 months. Once born, the absolute dependency of the calf upon the mother lasts from one to two years. Sexual maturity is achieved at around seven to ten years of age. The length of the developmental phases of a whale's early life varies between different whale species.{{sfn|Johnson|Wolman|1984}}

As with humans, the whale [[R/K selection theory|mode of reproduction]] typically produces but one offspring approximately once each year. While whales have fewer offspring over time than most species, the probability of survival for each calf is also greater than for most other species. Female whales are referred to as "cows." Cows assume full responsibility for the care and training of their young. Male whales, referred to as "bulls," typically play no role in the process of calf-rearing.

Most baleen whales reside at the poles. To prevent the unborn baleen whale calves from dying of frostbite, the baleen mother must migrate to warmer calving/mating grounds. They will then stay there for a matter of months until the calf has developed enough blubber to survive the bitter temperatures of the poles. Until then, the baleen calves will feed on the mother's fatty milk.{{sfn|Zerbini et al.|2006}}

With the exception of the humpback whale, it is largely unknown when whales migrate. Most will travel from the Arctic or Antarctic into the [[tropics]] to mate, calve, and raise their young during the winter and spring; they will migrate back to the poles in the warmer summer months so the calf can continue growing while the mother can continue eating, as they fast in the breeding grounds. One exception to this is the [[southern right whale]], which migrates to [[Patagonia]] and western New Zealand to calve; both are well out of the tropic zone.{{sfn|Kennedy|2008|p=966}}

===Sleep===
{{Further|Sleep in animals}}
Unlike most animals, whales are conscious breathers. All mammals sleep, but whales cannot afford to become unconscious for long because they may drown. While knowledge of sleep in wild cetaceans is limited, toothed cetaceans in captivity have been recorded to sleep with one side of their brain at a time, so that they may swim, breathe consciously, and avoid both predators and social contact during their period of rest.{{sfn|Miller et al.|2008|pp=21–23}}

A 2008 study found that sperm whales sleep in vertical postures just under the surface in passive shallow "drift-dives", generally during the day, during which whales do not respond to passing vessels unless they are in contact, leading to the suggestion that whales possibly sleep during such dives.{{sfn|Miller et al.|2008|pp=21–23}}