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Whale

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This article is about a marine mammal. For other uses, see Whale (disambiguation).
Whale
Temporal range: 50–0 Ma
Eocene – Recent
Southern right whale.jpg
South atlantic right whale breaching
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Eutheria
Order: Cetacea
Subgroups
Cypron-Range Physeter macrocephalus.svg
Range map

Whales, derived from Proto-Germanic word hwæl, are a widely distributed and diverse group of fully aquatic marine mammals. They comprise the extant families Cetotheriidae (whose only living member is the pygmy right whale), Balaenopteridae (the rorquals), Balaenidae (right whales), Eschrichtiidae (the gray whale), Monodontidae (belugas and narwhals), Physeteridae (the sperm whale), Kogiidae (the dwarf and pygmy sperm whale), and Ziphiidae (the beaked whales).[1][2] There are 40 extant species of whales. The two suborders of whales, Mysticeti and Odontoceti, are thought to have split up around 34 million years ago.[3] Whales belong to the clade Cetartiodactyla and their closest living relative is the hippo having diverged about 40 million years ago.[4]

Whales range in size from the 2.6 metres (8.5 ft) and 135 kilograms (298 lb) dwarf sperm whale to the 34 metres (112 ft) and 190 metric tons (210 short tons) blue whale, which is also the largest creature on earth. Several species exhibit sexual dimorphism, in that the females are larger than males. They have streamlined bodies and two limbs that are modified into flippers. Though not as flexible or agile as seals, whales can go at incredibly fast speeds, up to 20 knots. Balaenopterids (rorquals) use their throat pleats to expand their mouth to take in huge gulps of water.[5] Balaenids have huge heads that can make up 40% of their body mass to take in huge amounts of water.[6] Odontocetes have conical teeth designed for catching fish or squid. Mysticetes have a well developed sense of "smell", whereas Odontocetes have well-developed senses—their hearing that is adapted for both air and water, and can survive even if they're blind. Some species are well adapted for diving to great depths. They have a layer of fat, or blubber, under the skin to keep warm in the cold water.

Although whales are widespread, most species prefer the colder waters of the Northern and Southern Hemispheres, and migrate to the equator to give birth. Odontocetes feed largely on fish and squid; but a few, like the sperm whale, feed on large invertebrates, such as giant squid.[7] Grey whales are specialized for feeding on bottom-dwelling mollusks.[8] Male whales typically mate with multiple female every year, but females only mate every two to three years.[9] Calves are typically born in the spring and summer months and females bear all the responsibility for raising them. Mothers of some species fast and nurse their young for a relatively long period of time. Whales produce a number of vocalizations, notably the songs of the humpback whale.

The meat, blubber and baleen of whales have traditionally been used by indigenous peoples of the Arctic. Whales have been depicted in various cultures worldwide, notably, the Inuit and the coastal peoples of Vietnam and Ghana; they sometimes hold whale funerals.[10] Small whales, such as belugas, are commonly kept in captivity and are even sometimes trained to perform tricks. Once relentlessly hunted by commercial industries for their products, whales are now protected by international law. The North atlantic right whale have become nearly extinct in the past century with a population of 450, and the north pacific grey whale population is ranked Critically Endangered by the IUCN.[11] Besides whaling, they also face threats from bycatch and marine pollution (anything from trash bags to oil contamination).

Taxonomy

Cladogram of Cetacea within Artiodactyla

Cetaceans are divided into two suborders:

  • The largest suborder, Mysticeti (baleen whales), is characterised by the presence of baleen, a sieve-like structure in the upper jaw made of keratin, which it uses to filter plankton from the water.
  • Odontocetes (toothed whales) bear sharp teeth for hunting.

Cetaceans and artiodactyls now are classified under the super-order Cetartiodactyla, which includes both whales and hippopotami. The hippopotamus is the whale's closest living relatives.[12]

Mysticetes

Mysticetes are also as baleen whales. These animals lack conical teeth and are incapable of catching larger prey, which forces them to follow krill or plankton migrations. Some whales, such as the humpback reside at the poles where they feed on a reliable source of schooling fish and krill.[13] These animals rely on their well-developed flippers and tail fin to propel themselves through the water; they swim by moving their fore-flippers and tail fin up and down. Whale ribs loosely articulate with their thoracic vertebrae at the proximal end, but they do not form a rigid rib cage. This adaptation allows their chest to compress during deep dives opposed to resisting the forces of water pressure during dives into the depths.[14] Mysticetes consist of four types: rorqual whales (Balaenopterids), right whales (Balaenids), cetotheres, and grey whales (Eschrichtiidaes).

Balaenopterids are also known as rorquals. These animals rely on their huge throat pleats to gulp huge amounts of water at a time. These throat pleats extend from the mouth to the naval. The extra skin contained is used during feeding when huge amounts of water flood the whale's mouth, allowing them to expand their mouth, and feed more effectively. Balaenopterids consists of two genera and eight species.[5]
Balaenids are also known as right whales. These animals rely on their huge heads to take in massive amounts of water at a time. Their heads can make up as much as 40% of their body mass. Their huge head and, likewise, huge mouth allows them to take in huge amounts of water, allowing them to feed more effectively.[6]
Eschrichtiidaes have one living member: the gray whale. They're bottom feeders, mainly eating crustaceans and benthic invertebrates. They turn on their side and take in huge amounts of water mixed with sediment, and strain it all out, leaving only their prey. This is a very efficient method of hunting since it has no major competitors.[15]

Odontocetes

Odontocetes are also known as toothed whales due to the presence of teeth as opposed to their counterparts, the Mysticetes. These animals rely on their well-developed sonar to find their way in the water. For locomotion, toothed whales send out ultra-sonic clicks using their melon, which then in turn bounce back at the whale. These vibrations are received through fatty tissues in the jaw, which is then rerouted into the ear-bone and into the brain where the vibration are interpreted.[16] All toothed whales are opportunistic, meaning they'll eat anything they can fit in their throat (since they can't chew). These animals rely on their well-developed flippers and tail fin to propel themselves through the water; they swim by moving their fore-flippers and tail fin up and down. Whale ribs loosely articulate with their thoracic vertebrae at the proximal end but, they do not form a rigid rib cage. This adaptation allows their chest to compress during deep dives opposed to resisting the forces of water pressure during dives into the depths.[14] Odontocetes consist of four groups: narwhals and belugas, sperm whales, dwarf and pygmy sperm whales, and beaked whales.
Monodontids consists of two species: belugas and narwhals. They both reside in the frigid arctic and, likewise, both have large amounts of blubber. Belugas, being white, hunt in large pods near the surface and around pack ice; their coloration acting as camouflage. Narwhals, being black, hunt in large pods in the aphotic zone, but their underbelly still remains white to remain camouflaged when something is looking directly up at them. They have no dorsal fin to prevent collision with pack ice.[17]
Physeteridaes are also known as sperm whales. Sperm whales are the largest of the Odontocetes, and spend a large portion of their life hunting squid in the depths, only surfacing for air. These animals don't require any degree of light at all, in fact, blind sperm whales have been caught in perfect health.[18]
Ziphiidaes are also known as beaked whales. Beaked whales comprises 22 species. Each species is minutely different, but have relatively the same hunting style. These whales use a sort of suction technique, aided by a pair of grooves on the underside of their head, which is not unlike the throat pleats on the rorqual whales.[19]

Extinct genera

Evolution

Basilosaurus skeleton

All cetaceans, including whales, dolphins, and porpoises, are descendants of land-dwelling mammals of the artiodactyl order (even-toed ungulates). Both are related to the Indohyus, an extinct chevrotain-like ungulate, from which they split approximately 48 million years ago.[23][24] These primitive cetaceans first took to the sea approximately 50 million years ago and became fully aquatic by 5–10 million years later.[25] Their features became adapted for living in the marine environment. Major anatomical changes include streamlining of the body, the migration of the nasal openings toward the top of the cranium, the shrinking and eventual disappearance of the hind limbs, the modification of the forelimbs into flippers, and the growth of flukes on the tail.

Today, the whales closest living relative is the hippo. Whales and hippos share a semi-aquatic ancestor that branched off from other artiodactyls some 60 million years ago.[26] Around 40 million years ago, a common ancestor between the two branched off into cetacea and anthracotheres; anthracotheres went extinct at the end of the pleistocene two-and-a-half million years ago, leaving only one lineage left: the hippo.[27]

Archaeocetes

Evolution of whales
Indohyus (cca 49-48 Ma)
Pakicetus (cca 49-48 Ma)
Ambulocetus (cca 49-48 Ma)
Kutchicetus (cca 48 Ma)
Protocetus (cca 45 Ma)
Dorudon (cca 35 Ma)
Squalodon (Odontoceti) (cca 33-14)
Janjucetus (Mysticeti) (cca 25 Ma)

Archaeoceti is a suborder comprising ancient whales. These ancient whales are the predecessors of modern whales, stretching back to their first ancestor that spent their lives near (rarely in) the water. Likewise, the archaeocetes can be anywhere from near fully terrestrial to semi-aquatic to fully aquatic,, but what defines an archaeocete is the presence of features not present in modern whales; this would include visible legs or asymmetrical teeth. [28]

Indohyus was a small chevrotain-like animal that lived about 48 million years ago in what is now Kashmir.[29] It belongs to the family Raoellidae, and is believed to be the closest sister group of cetacea.[30] This herbivorous creature shared some whale-like traits, most notably the involucrum, a bone growth pattern found exclusively in cetaceans.[31] It also showed signs of adaptations to aquatic life, including a thick and heavy outer coating and dense limb bones that act as ballasts, which are similar to the adaptions found in modern creatures such as the hippopotamus; this suggests that, when in danger, it dived into the water and stayed in there for many minutes.[32][33][34][35][36]

Pakicetus was a terrestrial hoofed mammal that is thought to be the one of the earliest known whales, with Indohyus being the closest sister group.[37] It belonged to the Pakicetidae family. They lived around 50 million years ago. Their fossils were first discovered in North Pakistan in 1979, in what was the Tethys Sea. After the initial discovery, more fossils were found, all in the fluvial deposits in northern Pakistan and northwestern India. Based on this discovery, pakicetids most likely lived in an arid environment with ephemeral streams and moderately developed floodplains millions of years ago. Their skeleton implies a running lifestyle, but stable oxygen isotopes analysis shows that they lived near freshwater (and probably foraged in freshwater). Their diet probably included land animals that approached water or some freshwater aquatic organisms that lived in the river.[34][35][36]

Ambulocetus natans, which lived about 49 million years ago, was discovered in Pakistan in 1994 and belonged to the Ambulocetidae family. It was probably amphibious, and resembled the crocodile in its physical appearance; likewise, it was probably no longer herbivorous.[38] In the Eocene, ambulocetids inhabited the estuaries of the Tethys sea in northern Pakistan.[30] The fossils of ambulocetids are always found in near-shore shallow marine deposits associated with abundant marine plant fossils.[39] Although they are found only in marine deposits, their oxygen isotope values indicate that they drank a range of water with different degree of salinity, with some specimens having no evidence of sea water consumption and others that did not ingest fresh water at the time when their teeth are fossilized. It is clear that ambulocetids tolerated a wide range of salt concentrations and, therefore, represent a transitional phase of whale ancestors between fresh water and the ocean. In addition to this, they used a new hearing method allowing them to better hear underwater; sound traveled through soft tissue in the jaw leading to the ear. Modern whales use this system today.[34][35][36]

Kutchicetus evolved about 45 million years ago, belonged to the Remingtonocetidae family and was first described in 1986. It was probably amphibious, more so than its ancestors, of course. It had a much more flattened vertebrae than Ambulocetus natans, which would've supported an otter-like tail; the hip and vertebrae were still fused together, meaning they still walked on land. Its fossils were found in sediment that formed in shallow seas protected by barrier islands, meaning it had ventured into the oceans. Their eyes, much like Ambulocetus natans, were at high up on the skull, meaning they had a crocodile-like posture. The presence of foramina near the tip indicates they had whiskers. Their skull also had a very large sagittal crest, meaning they had a lot of room for jaw muscles; nobody knows exactly why they had this.[34][35][40]

Protocetus evolved around 43 million years ago, belonged to the Protocetidae family and was first described in 1908. It was more suited for a marine environment in comparison to its ancestors, but, nonetheless, still was amphibious. They had their pelvis only loosely connected to their sacral vertebrae, which allowed for greater movement in water, but it made them clumsy on land. It is thought they walked much like seals. They also had their nostrils further up their snout; this would eventually be at the top of their head. A fossil of Maiacetus, another protocetid, showed the fetus positioned for head-first delivery, indicating they gave birth on land; if they did give birth in the seas, the baby would be positioned tail-first to reduce risk of drowning.[41] Protocetids were the first whale ancestors to leave India.[35]

Basilosaurus, which lived about 35 million years ago, belonged to the Basilosauridae family, and are sometimes referred to as zeuglodons. They were discovered in 1868 in marine deposits, and their bones are found in Pakistan, the Middle East, and North America. Their pelvis was completely detached from their vertebrae, meaning they could no longer support themselves on land; they did, however, have very small feet containing three digits that, possibly, was used during courtship. Their nostrils were now at the top of their head, and the earbone structure indicates that it could hear very well in its marine environment. Their forelimbs were flippers, and their vertebrae suggests they had tail flukes. Their stomach contents indicated that they ate fish.[34][35]

Dorudon, which lived 35 million years ago, belonged to the Basilosauridae family. They were discovered in 1923 in marine deposits, and their bones are found worldwide. Their pelvis was completely detached from their vertebrae and their hind limbs were tiny, meaning they could no longer support themselves on land. Its nostrils were now at the top of its head, and they could, like modern whales, hear very well underwater. Their forelimbs were flippers. Their stomach contents indicated that they ate fish. They are suspected to have been preyed upon by Basilosaurus, given their major injuries sustained during their lifetime.[35][42]

Toothed or Baleen

Odontocetes (toothed whales) and Mysticetes (baleen whales) split into two separate suborders around 34 million years ago.[3]

The adaptation of echolocation defines when toothed whales split apart from baleen whales, and distinguishes modern toothed whales from ancient toothed whales. Modern toothed whales don't rely on their sense of sight, but rather on their sonar to hunt prey. Echolocation also allowed toothed whales to dive deeper in search of food, with light no longer necessary for navigation, which opened up new food sources. Some whales sought prey in the photic zone of the open oceans, whereas other toothed whales dove down into the depths in search of squid and benthic crustaceans, though food is hard to find in the vast bottom of the sea.[34]

The earliest of baleen whales contained both teeth and baleen in their jaws, as with llanocetus. The earliest whale with only baleen was found in New Zealand, and it was 26 million years old. Baleen plates are used to seethe the water in search of plankton and krill, allowing for a greater variety of food available than toothed whales. These microscopic organisms reside near the surface of the water, and baleen whales are forced to follow their migratory patterns; plankton and krill often reside at the poles, which many species of whales do reside there for the most part. Arctic whales, however, have go to warmer waters to give birth or risk their young dying of frostbite. The poles have some advantages however; small eobalaenids escaped predation by sharks, such as Megalodon among others, by residing in colder waters they not dare venture into; competition for krill and small fish is sparse, besides the presence of other whale species.[34]

Anatomy

Features of a blue whale

Whales have torpedo shaped bodies with non-existent external ear flaps, flat heads, non-flexible necks, limbs modified into flippers, and a large tail fin. Whale skulls have small eye orbits, long snouts (with the exception of Monodontids and Ziphiidaes) and eyes placed on the sides of its head. Odontocetes, such as the sperm whale, possess teeth with cementum cells overlying dentine cells. Unlike human teeth, which are composed mostly of 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 whale bone, as opposed to teeth, made of keratin. Mysticetes have two blowholes, whereas Odontocetes contain only one. Breathing involves expelling stale airfrom the blowhole, forming an upward, steamy spout, followed by inhaling fresh air into the lungs; a humpback whale's lungs can hold about 5,000 liters of air.[43][44] Spout shapes differ among species, which facilitates identification.[45][46]

Whales range in size from the 2.6 metres (8.5 ft) and 135 kilograms (298 lb) dwarf sperm whale to the 34 metres (112 ft) and 190 metric tons (210 short tons) 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.

All whales have a thick layer of blubber. In species that live near the poles, the blubber can be as thick as 11 inches. 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 whales body weight. Calves are born with only a thin layer of blubber, but some species compensate for this with thick lanugos.[47]

Whales have a two-to-three-chambered-stomach that is similar in structure to terrestrial carnivores. Mysticetes contain a proventriculus as an extension of the oesophagus; this contains stones that grind up food. They also have fundic and pyloric chambers.[48]

Locomotion

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 sperm whales and baleen whales) possess discrete rudimentary appendages, which may contain feet and digits. Whales are fast swimmers in comparison to seals, who typically cruising at 5–15 kn (9–28 km/h; 6–17 mph); the fin whale, in comparison, can travel at speeds up 47 km/hr and the sperm whale can reach speeds of 35 km/hr. The fusing of the neck vertebrae, while increased stability when swimming at high speeds, decreased flexibility; they can't turn their head.[49][50] When swimming, whales rely on their tail fin 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 log out of the water, which may allow then to travel faster. Their skeletal anatomy allows them to be incredibly fast swimmers. Most species have a dorsal fin.[51][52]

Whales have several adaptions for diving to great depths. In addition to their streamlined bodies, they can slow down their heart rate to conserve oxygen, blood is rerouted from tissue tolerant of water pressure to the heart and brain among other organs, and hemoglobin and myoglobin store oxygen in body tissue; they have twice the concentration of myoglobin than hemoglobin.

Senses

The whale ear has specific adaptations to the marine environment. In humans, the middle ear works as an impedance equalizer between the outside air's low impedance and the cochlear fluid's high impedance. In aquatic mammals, such as whales, 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.[53] The whale ear is acoustically isolated from the skull by air-filled sinus pockets, which allow for greater directional hearing underwater.[54][55]

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 and cone cells, meaning they can see in both dim and bright light, but they have far more rod cells than they do cone cells. Whale do, however, lack short wave-length sensitive visual pigments in their cone cells indicating a more limited capacity for color vision than most mammals.[56] 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. In water, whales can see around 10.7 metres (35 ft) ahead of itself, but, of course, they have a smaller range above water. They also have glands on the eyelids and outer corneal layer that act as protection for the cornea.[55][57]

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.[55][58]

Whales aren't thought to have a good sense of taste due to the atrophied, degenerated, or lack thereof taste-buds. On observation, however, some toothed whales have a preference over 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.[55][59]

Life history and behaviour

Socialization

Whales are known to teach, learn, cooperate, scheme, and grieve.[60] The neocortex of many species of whale is home to elongated spindle neurons that, prior to 2007, were known only in hominids.[61] In humans these cells are involved in social conduct, emotions, judgment, and theory of mind.[62] 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.[63]

Males are called 'bulls', females, 'cows' and all newborns, 'calves'. Most species do not maintain fixed reproductive partnerships. Females have several mates each season.[64] The female usually delivers a single calf, which is birthed tail-first to minimize the risk of drowning. Whale cows nurse by squirting milk into the mouths of their young. This milk is so rich in fat that it has the consistency of toothpaste.[64] In many species, nursing continues for more than a year and is associated with a strong bond between mother and calf. Reproductive maturity typically occurs at seven to ten years. This mode of reproduction produces few offspring, but increases the survival probability of each one.

Recording of Humpback Whales singing and Clicking.

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Some species, such as the humpback whale, communicate using melodic sounds, known as whale song. These sounds may be extremely loud, depending on the species. Humpback whales only have been heard making clicks, while toothed whales (Odontoceti) use echolocation that may generate approximately 20,000 watts of sound (+73 dBm or +43 dBw)[65] and be heard for many miles. Whale vocalization is likely to serve many purposes, including echolocation, mating, and identification.[66]

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 producing human speech likely takes considerable effort.[67]

Many whales exhibit behaviours that expose large parts of their bodies to the air, such as breaching and tail slapping. Sounding is a term used for whales diving. Typically it is only used for longer dives. Before sounding, whales typically stay close to the surface for a series of short, shallow dives while building their oxygen reserves. They then make a sounding dive.

Foraging and predation

All whales are carnivorous and predatory. Odontocetes, as a whole, mostly feed on fish and cephalopods, and then followed by crustaceans and bivalves. All species are generalist and opportunistic feeders. Mysticetes, as a whole, mostly feed on krill and plankton, followed by crustaceans and other invertebrates. A few are specialists. Examples include the blue whale, which eats almost exclusively krill, the minke whale, which eats mainly schooling fish, the sperm whale, which specialize on squid, and the grey which feed on bottom-dwelling invertebrates.[5] The elaborate baleen "teeth" of filter-feeding species, mysticetes, allow them to remove water before they swallow their planktonic food by using the teeth as a sieve.[64] Usually whales hunt solitarily, but they do sometimes hunt cooperatively in small groups. The former behavior is typical when hunting non-schooling fish, slow-moving or immobile invertebrates or endothermic prey. When large amounts of prey are available, whales such as certain mysticetes hunt cooperatively in small groups.[68] Some cetaceans may forage with other kinds of animals, such as other species of whales or certain species of pinnipeds.[69]

Large whales, such as mysticetes, aren't usually subject to predation, but smaller whales, such as Monodontids or Ziphiidaes, are. These species are preyed on by the killer whale or orca. To subdue and kill whales, orcas continuously ram them with their heads; this can sometimes kill bowhead whales, or at the very least, severely injure them. Other times they corral the narwhals or belugas into a sort of bait ball before striking. They are typically hunted by groups of 10 or fewer orcas, but they are seldom attacked by an individual. Calves are more commonly taken by orcas, but adults can be targeted as well.[70]

These small whales are also targeted by terrestrial predators. The polar bear is well adapted for hunting Arctic whales and calves. Bears are known to use sit-and-wait tactics as well as active stalking and pursuit of prey on ice or water. Whales lessen the chance of predation by gathering in groups. This however means less room around the breathing hole as the ice slowly closes the gap. When out at sea, whales seals dive out of the reach of surface-hunting orcas.[71]

Sleep

Photo of humpback whale with most of its body out of the water and its pectoral fins extended
A humpback whale breaching

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, avoid both predators and social contact during their period of rest.[72]

A 2008 study found that wild sperm whales (Physeter macrocephalus) 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.[73]

Whale pump

"Whale pump" - the role played by whales in nutrient recycling in the oceans

A 2010 study considered whales to be a positive influence to the productivity of ocean fisheries, in what has been termed a "whale pump." Whales carry nutrients such as nitrogen from the depths back to the surface. This functions as an upward biological pump, reversing an earlier presumption that whales accelerate the loss of nutrients to the bottom. This nitrogen input in the Gulf of Maine is "more than the input of all rivers combined" emptying into the gulf, some 23,000 metric tons each year.[74][75] Whales defecate at the oceans surface and this excrement is important for fisheries because it is rich in iron and nitrogen. The whale faeces are liquid and instead of sinking, they stay at the surface where phytoplankton feed off it.[76][77]

Whale fall

Main article: Whale fall

Upon death, whale carcasses fall to the deep ocean and being massive, with body weights of the range 30 to 160 tonnes (30,000 to 160,000 kg), provide a substantial habitat for marine creatures. Evidence of whale falls in present day and fossil records shows that deep sea whale falls support a rich assemblage of creatures, with a global diversity of 407 species as per Smith & Baco (2003), comparable to other neritic biodiversity hotspots, such as cold seeps and hydrothermal vents.[78]

Deterioration of whale carcasses happens though a series of three stages. Initially, moving organisms such as sharks and hagfish, scavenge the soft tissues at a rapid rate over a period of months, and as long as two years. This is followed by the colonisation of bones and surrounding sediments (which contain organic matter) by enrichment opportunists, such as crustaceans and polychaetes, throughout a period of years. Finally, sulfophilic bacteria reduce the bones releasing hydrogen sulfide enabling the growth of chemoautotrophic organisms, which in turn, support other organisms such as mussels, clams, limpets, and sea snails. This stage may last for decades and supports a rich assemblage of species, averaging 185 species per site as per Smith & Baco (2003).[78]

Species

Main article: List of whale species

Baleen whales

There are 14 recognized species of baleen whales: Antarctic minke whale, the blue whale, bowhead whale, Bryde's whale, common minke whale, fin whale, gray whale, humpback whale, northern right whale, Omura's whale, pygmy right whale, sei whale, and southern right whale.[79]

Species Description Image
Blue whale (Balaenoptera musculus) status EN The blue whale is the largest animal that ever lived on Earth, much larger than the largest dinosaur. This whale has been extensively hunted in the past. Between 1930 and 1971, about 280,000 blue whales have been killed. In 1966, when it became obvious not many blue whales were left, the International Whaling Commission (IWC) declared the blue whale a protected species. Blue whales produce very low frequency sounds (even below 20 Hz), which can be detected over large distances.[80] Average length is 24 to 27 m (79 to 89 ft). The largest whale found was 33.58 m (110.2 ft) long. Females are larger than males. Typical weight is 100 to 120 metric tons (110 to 130 short tons), up to 190 metric tons (210 short tons). Average age is 70 to 90 years. The skin is blue-grey coloured, mottled with grey-white. The large body is very broad. There is a large ridge on the head leading from the tip of the snout to the blowholes. The region of the blowholes is raised. A very small dorsal fin is located about 25% of the length in front of the tail flukes. The flippers are long and thin. The tail flukes are relatively small. There are 55-88 grooves extending from the chin to the navel. These grooves allow the mouth to extend considerably during feeding. The tongue, palate and baleen are black. The baleen is wide and relatively short (less than 1 metre (3.3 ft) in length). While it has a worldwide distribution, it feeds in polar waters in summer and spends the winter in tropical and subtropical waters. Blue whales usually swim alone or in groups of two or three animals. They may group together on feeding grounds and form mixed-species groups with fin whales. The blue whale feeds almost exclusively on krill, rarely on small fish, such as capelin and sardines. Blue whales are rorquals, meaning they have long throat pleats that extend from the mouth to the naval; these skin flaps allow the whales mouth to take in huge amounts of water and sift through the krill and plankton within it.[5] Abundance: probably about 11,200 worldwide. In the North Atlantic there are only a few hundred blue whales left. Although the numbers are increasing, the blue whale is still endangered.[11][81] Anim1754 - Flickr - NOAA Photo Library.jpg
Bowhead whale (Balaena mysticetus) status LC The bowhead whale was a target of early whaling operations. It was hunted for its oil and baleen. The Inuit people occasionally take a few whales in the Bering/Chukchi/Beaufort Sea area.[82] Typical length is 14 to 18 metres (46 to 59 ft). Females are slightly larger than males. Average weight is 60 to 90 metric tons (66 to 99 short tons). Average age is 100 to 200 years, making it one of the longest-lived creatures alive today. The bowhead whale is a very stocky animal with a large head. The mouth is bowed strongly upward. The skin is smooth and free of parasites. They are blue-black in colour with random light patches on the stomach and lower jaw. There is no dorsal fin. The flippers are relatively small and paddle-shaped. The tail flukes are wide and pointed. The baleen plates are narrow (30 cm) and very long, up to 4.3 metres (14 ft). Its lives in Arctic waters, near pack ice. There are three main bowhead whale areas: Spitsbergen, Davis Strait, Okhotsk Sea and Bering/Chukchi/Beaufort Sea. Usually the bowhead is seen alone or in small groups of up to three individuals. It feeds on small crustaceans. Bowhead whales are balaenids, meaning they use their massive baleen plates, which are the largest (4.5 metres (15 ft)), to take in huge amounts of water; balaenids lack throat pleets, but they make up for it in head size which makes up around 40% of their body mass.[6] The Bering/Chukchi/Beaufort Sea has about 7,800 individuals. The Spitsbergen stock is probably extinct and the populations in the other areas have probably only a few hundred individuals.[11][81] A bowhead whale breaches off the coast of western Sea of Okhotsk by Olga Shpak, Marine Mammal Council, IEE RAS.jpg
Bryde's whale (Balaenoptera edeni)
status DD
Bryde's whale is easily confused with the sei whale. At close range, Bryde's whale can be easily recognised by the three parallel ridges on the head. The sei whale has only one central ridge. Bryde's whale is known to breach often in some areas. Bryde's whale is the least hunted of the rorqual species, mainly because it inhabits tropical and subtropical waters that were closed to whaling operations, because other species had been depleted in the area.[83] Average length is 11.5 to 14.5 metres (38 to 48 ft) and average weight is 10 to 20 metric tons (11 to 22 short tons). Females can live up to 52 years of age and males up to 55 years of age. Bryde's whale has 3 ridges on the head leading from the tip of the upper jaw to the blowholes. The Bryde's whale is dark grey on the back and lighter on the belly. They sometimes have light oval scars, caused by cookiecutter sharks. The dorsal fin is small and very curved. The flippers are medium-sized and thin, and somewhat rounded at the tip. The tail flukes are almost identical to those of the blue whale. It inhabits tropical and subtropical waters, between 40N and 40S latitude. It is usually alone or in groups of up to 10. They feed mainly on schooling fish, crustaceans and squid. Bryde's whales are rorquals, meaning they have long throat pleats that extend from the mouth to the naval; these skin flaps allow the whales mouth to take in huge amounts of water and sift through the krill and plankton within it.[5] The North Pacific population is probably about 20,000-30,000 individuals. Not much is known about other areas.[11] Brydeswhale sophiewebb-swfsc-star2006.jpg
Fin whale (Balaenoptera physalus) status EN The fin whale is a fast swimmer, reaching speeds of 47 km/hr. It occasionally jumps clear of the water but does so less than other rorquals. They hardly ever show their tails before diving deep.[84] Size is 18 to 22 metres (59 to 72 ft), up to 27 metres (89 ft). Females are larger than males. Northern hemisphere fin whales are on average 1 12 metres (4.9 ft) shorter than Southern hemisphere fin whales. Average age is 60 to 100 years. Weight ranges from 30 to 75 metric tons (33 to 83 short tons). The fin whale is a long and slender whale. The head resembles that of the blue whale. The fin whale is dark grey to brown in colour, with flanks that lighten towards the belly. The dark colour extends farther down on the left side than on the right. Most animals have a light chevron just behind the head. The large dorsal fin (60 cm high) is placed far back. The flippers are thin and pointed. The tail flukes are large, thin and pointed and look like blue whale flukes. It has a worldwide distribution, in deeper water. It is usually found in groups of up to 10, but larger groups (up to 100) are not uncommon. Its diet is mainly small crustaceans, but Northern hemisphere fin whales also feed on fish. Fin whales are rorquals, meaning they have long throat pleats that extend from the mouth to the naval; these skin flaps allow the whales mouth to take in huge amounts of water and sift through the krill and plankton within it; they've been seen herding fish into bait balls before engulfing them.[5][85] There are roughly 100,000 in the southern hemisphere, but only 30,000 in the northern hemisphere, split two to one between the North Pacific and the North Atlantic.[11][81] LMazzuca Fin Whale.jpg
Gray whale (Eschrichtius robustus) status LC The gray whale spends the winter in the lagoons of Baja California, Mexico. In summer they move to Alaska to feed. They travel along the US coast and the grey whale migration can be seen from several land-based spots along the coast. The gray whale is one of the few species who have come back from the brink of extinction. After a period of intense whaling, the species was nearly extinct, but it has recovered to the point that the US has taken it off its endangered species list. This species is 13.5 to 15 metres (44 to 49 ft) in length and weighs up to 27 metric tons (30 short tons). Average age is 50 to 70 years. The grey whale is mottled grey all over. The skin on the back has large yellow and white coloured patches caused by parasites like barnacle and whale lice . The mouth is slightly bowed. They have more bristles on the tips of their upper and lower jaws than any other whale species. The grey whale has no dorsal fin but a number of bumps on the back and tail stock. The flippers are large and paddle-shaped. The baleen plates are yellowish and about 40 cm long, with long, thick bristles. It resides in the North Pacific only. The gray whale used to be present in the North Atlantic as well, but is now extinct there. In summer, they feed in the northern Bering Sea. During migration, females with calves swim together in groups of about 6 adults. Later in the migration, there are groups of three to five non-pregnant females with one or two males. The last on the migration are juvenile animals. The gray whale feeds on the bottom. The prey consists of crustaceans, molluscs and small fish. Grey whales are bottom feeders, meaning they dive down to the ocean floor and suck up the sediment; they then sift through the sediment for their prey. The Eastern population is probably about 21,000 individuals and is increasing in size at about 3.2% per year. The Western Pacific population is small, probably 100-200 individuals.[11][81] Gray whale Merrill Gosho NOAA2 crop.jpg
Humpback whale (Megaptera novaeangliae) status VU The humpback whale is probably one of the best known baleen whale species. The humpback whale is famous for its songs, of which even records have been made. The function of the songs is not clear. Most likely, the songs play a role in territorial behaviour and in courting. Only the males sing. These songs can be heard over large distances. Humpback whales have developed a unique way of catching fish: they dive down, then slowly circle to the surface, blowing bubbles on the way up. This will encircle the fish in a net of bubbles. The whales then surface with open mouths in the middle of the circle, gulping up the concentrated fish. Humpback whales migrate over large distances. In the North Pacific, Humpbacks spend the winter near Hawaii or Baja Californian and in summer, move to Alaska to feed.[86] This species is up to 19 metres (62 ft) long and weighs up to 48 metric tons (53 short tons). Average age is 40 to 100 years. The humpback whale is black all over, with very long flippers, which vary in colour from black to white. There are also lighter patches on the belly and chest. The underside of the tail flukes also have patterns, which are unique for each individual. From the blowhole to the tip of the snout and laterally towards the edges of the mouth there are conspicuous hair follicles on large bumps. The dorsal fin is small and set far back (about 2/3 of the body length). Its distribution is worldwide, but they follow fixed migration patterns. In the summer, they feed in the polar regions and they migrate to warmer waters in the winter for breeding. There are three isolated populations: North Pacific, North Atlantic and Southern Hemisphere. On the calving grounds, they usually form groups of about 10-12. During migration they travel in groups of three to four. They feed on krill, plankton, and small schooling fish. Humpback whales are rorquals, meaning they have long throat pleats that extend from the mouth to the naval; these skin flaps allow the whales mouth to take in huge amounts of water and sift through the krill and plankton within it.[5] There are about 5,500 in the North Atlantic, 2,500 in the North Pacific and about 12,000 in the Southern Hemisphere. There may also be a resident population of about 500 individuals in the Indian Ocean. The humpback whale is considered to be a vulnerable species.[11][81] Humpback Whale fg1.jpg
Minke whale (Balaenoptera acutorostrata, Balaenoptera bonaerensis) status LC The minke whale became the target of whaling operations when the larger whales had declined to a level that made hunting them commercially unattractive. With all the larger whales reduced in numbers, the minke whales could multiply. Commercial fisheries for minke whales has restarted in Norway. In 1996, Norwegian whalers took 116 minke whales and in 1997, 503. In Greenland, the indigenous people are allowed to take 465 minke whales in 2 years.[87] This whale species is 7 to 10 metres (23 to 33 ft), making it the smallest of the baleen whales. Average age is 30 to 50 years. They weigh 4.5 to 9 metric tons (5.0 to 9.9 short tons). The snout is pointed, and there is a clear under-bite. The back is black, whereas the belly region is white. They have a distinctive white band on the long, thin flippers. They have a well-developed curved dorsal fin, which looks like the dorsal fin of the bottlenose dolphin. Most Pacific animals have a light chevron on their flanks. It prefers temperate waters, around the world. They are usually found in small groups of 6 or less. They feed mainly on shoaling fish, and also on krill and plankton. Minke whales are rorquals, meaning they have long throat pleats that extend from the mouth to the naval; these skin flaps allow the whales mouth to take in huge amounts of water and sift through the krill and plankton within it.[5] In the North Pacific (B. acutorostrata) there are 18,000-27,000, in the Northeastern Atlantic (B. acutorostrata): 90-135,000, in the Central Atlantic (B. acutorostrata) about 60,000, and in the Southern Hemisphere (B. bonaerensis) 200-400,000.[11][81][88] Minke Whale (NOAA).jpg
Omura's whale (Balaenoptera omurai)
status DD
Omura's whale, sometimes referred to as the dwarf fin whale, is a very mysterious type of whale. Prior to 2003, omura's whale was thought to be a dwarf variation of bryde's whale, and as a result, very little is known about them. This species was originally identified by only ten or so individuals. Their colouration has been reported in some individuals to resemble the fin whale, hence its nickname. Males reach a length of a mere 8.2 to 10.1 metres (27 to 33 ft), and females reach 9.8 to 11.5 metres (32 to 38 ft), making Omura's whale one of the smallest baleen whales. Their average weight remains unknown, as well as their average age.[89] Based on sightings, they are thought to travel alone and, rarely, in pairs. Since they are rorquals, they are believed to feed predominately on schooling fish. Omura's whales are rorquals, meaning they have long throat pleats that extend from the mouth to the naval; these skin flaps allow the whales mouth to take in huge amounts of water and sift through the krill and plankton within it.[5] Their distribution remains unknown, but they are known to occupy the coasts of Japan, the Philippines, Indonesia, and are thought to live in the subtropical waters of the Indian ocean and the western Pacific ocean. Since this whale was discovered so recently, and their discovery was based upon nine individuals, the IUCN has listed them as "data deficient", meaning there are no accurate approximations for their population.[90] Bryde´s whale.jpg
Pygmy right whale (Caperea marginata) status DD The pygmy right whale is a very elusive species; they are rarely seen in the ocean and much of what is known about them comes from dead individuals that stranded themselves onto shore, and, as a result, little is known about them. This whale was once thought to be the last surviving member of the Neobalaenidae family, but its skull shape suggests that it is part of a very ancient family of whales called Cetotheres, which branched off from modern baleen whales somewhere between 17 million and 25 million years ago; the last member was thought to die out around two million years ago.[91] The name comes from its appearance, mainly the shape of the mouth.[92] Its length is 5.5 to 6.5 metres (18 to 21 ft) making it one of the smallest baleen whale species. Their average age remains unknown. It weighs 3 to 4 metric tons (3.3 to 4.4 short tons). The lower jaw is bowed and protrudes slightly. The body is stocky. They have a dark-coloured back, which becomes darker with age, and a pale belly. This whale has a prominent dorsal fin. The flippers are small and rounded and located under the body. The tail flukes are broad. The baleen plates are yellowish and are up to 70 cm in length. It is only known from the Southern hemisphere and usually is solitary. The stomach contents of beached whales identifies plankton and krill as a large part of their diet. Hunting behaviour is not known, but, given their small lungs, it is thought they hunt near the surface.[11][81][93] Caperea marginata 3.jpg
Right whale (Eubalaena glacialis, Eubalaena australis, Eubalaena japonica These whales were named right whales, because for the early whalers they were the right ones to catch. They are slow, have lots of fat and stay afloat when killed. Only when the right and bowhead whales were depleted and factory ships were developed did the hunt for the rorquals start.[94] This 11 to 18 metres (36 to 59 ft) long species weighs 30 to 75 metric tons (33 to 83 short tons). Their average lifespan remains unknown, but some speculate they can live to be as old as 80. The right whale is extremely fat. There are numerous callosities on the mouth and head, caused by whale lice. They are black with large white patches on the belly. They have no dorsal fin and their flippers are paddle-shaped. The tail flukes are very wide, thin and pointed. Its distribution is in temperate oceans worldwide. The Southern right whale (E. australis) can be found from the Antarctic to Australia and South America and into the Indian Ocean. The Northern right whale (E. japonica) is found in the North Pacific, from Japan and Baja California to the Aleutians. In the North Atlantic, the Northern atlantic right whale (E. glacialis) occurs from Florida and Spain in the South to Bear Island and Spitsbergen in the north. Its social structure is usually small groups of up to 5. They feeds mainly on krill and copepods. Right whales are balaenids, meaning they use their 500 massive baleen plates to take in huge amounts of water; balaenids lack throat pleets, but their head makes up around 40% of their body mass.[6] In the Northwest Atlantic about 1,000 are left; the Northeast Atlantic population is believed to be near extinction. The North Pacific population is probably nearly extinct. There are no signs of recovery in the Northern right whale populations. The total population of Southern right whales is probably about 1,500 and may be recovering slightly.[11][81] Southern right whale.jpg
Sei whale (Balaenoptera borealis) status EN The sei whale is probably the fastest swimmer among the baleen whales. It can reach speeds of close to 38 km/hr. The sei whale has been hunted extensively in the past. Because this whale resembles the Bryde's whale (only at close range can one see the single ridge on the head, whereas the Bryde's whale has 3 parallel ridges), combined quotas were set for these species until 1964. The catches were also recorded together. Consequently, there is no accurate catch statistics from before that date. In the 1960s, the annual catch of Sei whales was 10-15,000 per year. Hunting of sei whales was stopped in the 1970s.[95] Typical males are 12 to 18 metres (39 to 59 ft) long, while females are up to 20 metres (66 ft) long. Males weigh up to 22 metric tons (24 short tons), females up to 24 metric tons (26 short tons). Their average age is 50 to 70 years. The sei whale is dark grey on the back and also on the underside of the tail stock. The chin, throat and belly are white. This whale often has oval white marks, caused by lampreys and cookiecutter sharks. One long ridge runs from the tip of the upper jaw to the blowholes. The dorsal fin is large and placed far back (farther than that of the fin whale). It has a worldwide distribution, but not near the pack ice. It is usually seen alone or in pairs. When plenty of food is available they may form larger groups. Diet consists mostly of krill and other crustaceans. The sei whale also feeds on capelin, pollack (in Norwegian, they are called sei; the association with this fish gave the whale its name), anchovies, herring, cod and sardines. Sei whales are rorquals, meaning they have long throat pleats that extend from the mouth to the naval; these skin flaps allow the whales mouth to take in huge amounts of water and sift through the krill and plankton within it.[5] This species has been depleted by over-exploitation. After the end of commercial whaling for this species in 1980, no population estimates have been made. The North Atlantic population probably consists of a few thousand, the North Pacific population about 13,000 and the Antarctic populations about 40,000. This species is still vulnerable.[11] Sei whale mother and calf Christin Khan NOAA.jpg

Toothed whales

See also: Odontoceti

There are 72 species of toothed whale, which encompasses everything belonging to the suborder Odontecete. Excluding dolphins and porpoises, there are 26 (recognized) species of toothed whales.[96]

Species Description Image
Beaked whale (Berardius) Beaked whales are a member of the Ziphiidae family which encompasses 22 different species of whales (Andrew's beaked whale, Arnoux's beaked whale, Baird's beaked whale, Blainville's beaked whale, bottlenose whale, Cuvier's beaked whale, Deraniyagala's beaked whale, Gervais' beaked whale, Ginkgo-toothed beaked whale, Gray's beaked whale, Hector's beaked whale, Hubbs' beaked whale, Longman's beaked whale, Perrin's beaked whale, Pygmy beaked whale, Shepherd's beaked whale, Sowerby's beaked whale, Spade-toothed whale, Stejneger's beaked whale, Strap-toothed whale, and True's beaked whale [97]), all of which dive regularly to a depth surpassing 500 m (1,600 ft) to literally suck the life of their prey by using a suction system aided by a pair of grooves on the under its head which allow greater amounts of water to be in its mouth at one time. The Ziphiidae family is the most widespread of the cetaceans, encompassing the globes ocean, but generally inhabiting offshore areas of at least a depth of 300 m (980 ft). The beaked whale ranges from 4–13 m (13–43 ft), and weighing 0.9 to 13.6 metric tons (0.99 to 14.99 short tons). These whales are not dissimilar to dolphins, in that they both have beaks, have a bulging forehead, and are roughly the same dimensions as one. They do, however have differences, in that their tail fluke does not have a notch in it (excluding Shepherd's beaked whale). Species differentiation can be difficult, in that all species are quite similar, except minute differences in size, color, and beak size.[98]
Blainville's beaked whale
Beluga whale (Delphinapterus leucas)
status NT
The beluga is a white whale that inhabits the icy waters of the Arctic Ocean. To cope with the freezing temperatures of the Arctic, belugas have an enormous amount of blubber that makes up 40% of their body mass. Belugas are also unique among cetaceans in that their skin turns yellow in July when it's time to shed it. Belugas are opportunistic, in that they'll eat just about anything that can realistically fit in its mouth, which could include octopus, squid, crustaceans, shellfish, snails, sand worms, and fish. They use a variety of hunting methods; they can herd fish or forage near the bottom... Belugas give birth to one (rarely two) calves every two to three years, with gestation lasting around 15 months. They nurse for the first 18 months when their teeth grow in. Belugas are also known for their incredibly sized pods that can include several hundred individuals and are given their nickname "canary of the sea" due to their high inclination to vocalize. Historically, belugas have been hunted by natives, but in more recent times (18th and 19th centuries), belugas have been hunted, mainly for their melon oil which was used as a lubricant.[99] Males average about 1,500 kg (3,300 lb), whereas females average about 1,360 kg (3,000 lb). Males can reach lengths of 4.15 m (13.6 ft), whereas females reach about 3.55 m (11.6 ft). Their average lifespan is thought to range anywhere from 35 years to 50 years.[100]
Beluga whale
Dwarf sperm whale (Kogia sima)
status DD
Originally considered the same species as the pygmy sperm whale, a Smithsonian scientist determined they were two different species in 1966. The dwarf sperm whale is a smaller relative of Physeter macrocephalus and is almost the same as its closer cousin Kogia breviceps. Likewise, they have a spermaceti organ. This is a very elusive animal and, consequently, little is known about them. They are the only whales, apart from the pygmy sperm whale to use a sort of pseudo-ink, like squids, by releasing up to 12 gallons of a reddish/brown liquid when startled which is known as "the squid-tactic". This blurs the vision of its attacker, allowing the whale to escape unharmed. This whale has a false gill plate behind the eyes. These creatures are thought to dive to about 300 m (980 ft), and probably use echolocation to find their prey which includes squid, fish and crustaceans in the subtropical waters of the world. They are often seen logging near the surface at three knots. Dwarf sperm whales grow to be around 2.7 m (8 ft 10 in) in length, and weigh in at 135 to 270 kg (298 to 595 lb), with the females being slightly smaller than the males. They are thought to swim in pods of between six and ten individuals. Their population lies between 23,000 and 30,000 individuals in U.S. waters.[101]
Dwarf sperm whale
Narwhal (Monodon monoceros) status NT The narwhal is a torpedo shaped whale that inhabits the icy waters of the Arctic Ocean. Narwhals have two teeth in their upper jaw and, in males, the left tooth grows into a large spiral tusk made of ivory that can be 2.7 m (8 ft 10 in) long and weigh 10 kg (22 lb), giving it its nickname "the unicorn of the sea". Females, rarely however, can also grow tusks.[102] Native Inuit hunted them for their skin which is eaten raw with a layer of fat. In the 1980s, this practice increased, which drastically reduced the narwhal's population. Their diet consists primarily of Greenland halibut, Arctic cod, cuttlefish, shrimp and armhook squid. Narwhals are believed to swim in pods of up to 20 individuals, usually segregated by gender. Generally, gestation requires around 15 months, and the calf (rarely calves) is weaned off after 20 months. The average male measures 4.7 m (15 ft), whereas the average female measures 4 m (13 ft). The male narwhal, on average, weighs 1,600 kg (3,500 lb) and the average female weighs 900 kg (2,000 lb), of which one third is fat to insulate themselves from the icy waters of the Arctic Ocean. They're thought to live up to 50 years. The narwhal has a conservation status of Near Threatened with an estimated population anywhere between 25,000 individuals to 45,000 individuals.[103]
Narwhals breaching
Pygmy sperm whale (Kogia breviceps) status DD Originally considered the same species as the dwarf sperm whale, a Smithsonian scientist determined they were two different species in 1966. The pygmy sperm whale is a smaller relative of Physeter macrocephalus and is almost the same as its closer cousin Kogia sima. Likewise, they have a spermaceti organ. This is a very elusive animal and, consequently, little is known about them. They are the only whales, apart from the dwarf sperm whale to use a sort of pseudo-ink, like squids, by releasing up to 12 gallons of a reddish/brown liquid when startled which is known as "the squid-tactic". This blurs the vision of its attacker, allowing the whale to escape unharmed. This whale has a false gill plate behind the eyes. These creatures dive to about 300 m (980 ft), and probably use echolocation to find their prey which includes squid, fish and crustaceans in the subtropical and temperate waters of the world. They are often seen logging near the surface at three knots. Pygmy sperm whales grow to be around 3.5 m (11 ft) in length, and weigh in at 320 to 455 kg (705 to 1,003 lb), with the females being slightly smaller than the males. They are thought to swim in pods of up to seven individuals. The average lifespan of this whale is thought to be around 23 years. Their population remains unknown.[104]
Pygmy sperm whale depiction from the 19th century
Sperm whale (Physeter macrocephalus) status VU Sperm whales are known for their enormous heads, likewise their brains are the largest in the animal kingdom with a volume of 8,000 cm3 and weighs in at 7 kg (15 lb). These colossal creatures must dive as deep as 1,000 m (3,300 ft) in search of squid which makes up its diet, and to do such, they must hold their breath for 90 minutes. They do this frequently, due to their need to eat about 907 kilograms (1.000 short ton) of fish and squid per day. Female sperm whales congregate in pods of 15-20 individuals and remain in tropical waters year-round, whereas males travel alone in Arctic or Antarctic waters, feeding on the abundant squid, only migrating towards the equator to breed. Throughout the 18th and 19th centuries, sperm whales were heavily whaled for spermaceti (hence the name sperm whale), an oil that forms above its skull, which would be used in lubrication and lamp fuel; this ended in 1985 when the International Whaling Commission created a treaty between whalers, that practically ended it. Sperm whale oil was, and is, a valuable commodity. Sperm whales weigh up to 40 metric tons (44 short tons), and can be as long as 18 m (59 ft). Typically, they live to be 70 years old. The sperm whale is endangered with a population is dwindling at 300,000 individuals.[105][106]
Mother and baby sperm whales

Interaction with humans

Commercial

Dutch whalers near Spitsbergen, Abraham Storck, 1690

Belugas have been kept in captivity since 1861[107] and 1961,[108][109] respectively, for public display in a few locations.[110][111] They are popular due to their intelligence, trainability,[112][113] striking appearance,[114] playfulness in captivity,[115][116] and size. Belugas have also been kept captive for naval research in the US[117] and Russia.[118]

Most current captives were caught in the wild, since captive breeding has had limited success.[119] There is controversy over captivity,[110][120] with limited enrichment activities and tank sizes, though defenders say easy access for research[113][120][121][122] and public viewing are beneficial.[123] The whales have far larger family groups and ranges in the wild[124] than in captivity.

An estimated 13 million people went whale watching globally in 2008, in all oceans except the Arctic.[125][126] There are numerous rules and codes of conduct to minimize harassment of the whales.[127] Iceland, Japan and Norway have both whaling and whale watching industries. Whale watching lobbyists are concerned that the most inquisitive whales, which approach boats very closely and provide much of the entertainment on whale-watching trips, will be the first to be taken if whaling is done in the same areas.[128]

Negative

Map showing IWC non-members such as Canada and most Middle Eastern and African countries in white
World map of International Whaling Commission (IWC) members/non-members(member countries in blue)
Diagram showing the pre-whaling of 275,000, 1930s population of 30–40,000, mid-60s population of 650–2,000 and 1994 population of fewer than 5,000
World population graph of blue whales (Balaenoptera musculus)

Some species of large whales are listed as endangered by multinational organizations, such as CITES, as well as governments and advocacy groups. This status is due primarily to the impact of whaling. Whales have been hunted commercially since the seventeenth century for whale oil, whale meat, baleen, and ambergris (a perfume ingredient from the intestine of sperm whales).[129] More than two million whales were taken during the twentieth century,[130] and by the middle of that century, many populations were severely depleted.

The International Whaling Commission banned commercial whaling in 1986.[131] The ban is not absolute, and some whaling continues under the auspices of scientific research[131] (sometimes not proved[132]) or aboriginal rights. Current whaling nations are Norway, Iceland, and Japan as well as the aboriginal communities of Siberia, Alaska, and northern Canada.

Several species of small whales are caught as bycatch while fishing for other species. In the Eastern Tropical Pacific tuna fishery, thousands of dolphins drowned in purse-seine nets, until preventive measures were introduced. Gear and deployment modifications, and eco-labelling (dolphin-safe or dolphin-friendly brands of tuna), have contributed to a reduction in dolphin mortality by tuna vessels.[133]

Environmentalists speculate that advanced naval sonar endangers some cetaceans, including whales. In 2003, British and Spanish scientists suggested in Nature that the effects of sonar trigger whale beachings and they point to signs that such whales have experienced decompression sickness.[134] Responses in Nature the following year discounted the explanation.[135]

Mass beachings occur in many species, mostly beaked whales that use echolocation for deep diving. The frequency and size of beachings around the world, recorded throughout the last thousand years in religious tracts, and more recently in scientific surveys, have been used to estimate the population of various whale species by assuming that the proportion of the total whale population beaching in any one year is constant. Beached whales can give other clues about population conditions, especially health problems. For example, bleeding around ears, internal lesions, and nitrogen bubbles in organ tissue suggest decompression sickness.[60]

An autopsy on a beached pilot whale in Taiwan who later died even after being returned to water found large quantities of plastic bags and cellophane snack-wrappers in the whale’s stomach.[136] The researchers came to the conclusion that the region lacked food for cetaceans.

In culture

Whale weather-vane atop the Nantucket Historical Association Whaling Museum displaying a sperm whale

Whales were little understood for most of human history as little of their lives could be seen from the surface of the ocean.[137] Many cultures, even those that have hunted them, hold whales in awe and feature them in their mythologies. In China, Yu-kiang, a whale with the hands and feet of a human was said to rule the ocean.[138] In the Tyrol region of Austria, it was said that if a sunbeam were to fall on a girl entering puberty, she would be carried away in the belly of a whale.[139] Paikea, the youngest and favourite son of the chief Uenuku from the island of Mangaia (Cook Islands), was said by the Kati Kuri people of Kaikoura to have traveled from the Pacific Islands on the back of a whale many centuries before.[140] The whale features in Inuit creation myths. When 'Big Raven', a deity in human form, found a stranded whale, he was told by the Great Spirit where to find special mushrooms that would give him the strength to drag the whale back to the sea and thus, return order to the world.[138] In an Icelandic legend a man threw a stone at a fin whale and hit the blowhole, causing the whale to burst. The man was told not to go to sea for twenty years, but during the nineteenth year he went fishing and a whale came and killed him.[141] In East African legend, King Sulemani asked God that he might permit him to feed all the beings on earth. A whale came and ate until there was no corn left and then told Sulemani that he still was hungry and that there were 70,000 more in his tribe. Sulemani then prayed to God for forgiveness and thanked the creature for teaching him a lesson in humility.[138]

Some cultures associate divinity with whales, such as among Ghanaians and Vietnamese, who occasionally hold funerals for beached whales, a throwback to Vietnam's ancient sea-based Austro-Asiatic culture.[10][142][143][144]

The Bible mentions whales in Genesis 1:21, Job 7:12, Ezekiel and 32:2. The "sea monsters" in Lamentations 4:3 have been taken by some commentators to refer to marine mammals, in particular whales, although most modern versions use the word "jackals" instead.[145] The story of Jonah being swallowed by a "big Fish" is told both in the Qur'an and in the Bible.[146] The Old Testament contains the Book of Jonah and in the New Testament, Jesus mentions this story in Matthew 12:40.[147]

The engraving by William van der Gouwen shows a 20 m (65.6 ft) long whale, stranded on the Dutch coast between Scheveningen and Katwijk on 3 February 1598

And God Created Great Whales, written in 1970 by American composer Alan Hovhaness, is a work for orchestra and whale songs, including the recorded sounds of humpback, bowhead whales.[148] The song "Il n'y a plus rien", from French singer-songwriter Léo Ferré's eponymous album (1973), is an example of biomusic that begins and ends with recorded whale songs mixed with a symphonic orchestra and his voice.

The 1851 American novel, Moby-Dick by Herman Melville concerns a vexed captain's hunt for a gigantic white whale. Rudyard Kipling's 1902 Just So Stories includes the tale of "How the Whale got his Throat".[149] The film Whale Rider directed by Niki Caro has a Maori girl ride a whale in her quest to be a suitable heir to the chiefship.[150] An enormous whale called Monstro is the final antagonist featured in Walt Disney's 1940 animated film Pinocchio.

See also

References

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Further reading

External links