Narwhal

This article is about the species of whale. For the class of submarine, see Narwhal class submarine. For Barack Obama's 2012 get out the vote program, see Project Narwhal.

Narwhal
Illustration of two views of an individual
Size comparison with an average human
Conservation status
Near Threatened  (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Artiodactyla
Infraorder:	Cetacea
Family:	Monodontidae
Genus:	Monodon Linnaeus, 1758
Species:	Monodon
Binomial name
Monodon Linnaeus, 1758
The frequent (solid) and rare (striped) occurrence of narwhal populations

The narwhal, or narwhale (Monodon monoceros), is a medium-sized toothed whale and the animal with the largest canines. It lives year-round in the Arctic. One of two living species of whale in the Monodontidae family, along with the beluga whale, the narwhal males are distinguished by a long, straight, helical tusk, which is an elongated upper left canine. It was one of many species originally described by Carolus Linnaeus in his publication Systema Naturae. The cetaceans most closely related to narwhals and belugas are porpoises, which diverged from dolphins about 11 million years ago.

Like the beluga, narwhals are medium-sized whales. For both genders, including the male's tusk, the total body size can range from 3.95 to 5.5 metres (13.0 to 18.0 feet); the males are slightly larger than the females. The average weight of an adult narwhal is 800 to 1,600 kilograms (1,800 to 3,500 pounds). At around 11 to 13 years old, the males become sexually mature; for the females, sexual maturity happens when they are about 5 to 8 years old. Males are darker when born, becoming lighter in colour until they become almost pure white in old age. Narwhals do not have a dorsal fin, and their neck vertebrae are jointed like other mammals, not fused like dolphins and most whales. Belugas also have both features present. As an adaptation to reduce drag from the tusk, male narwhals have concave tail flukes with no sweep-back.

Found primarily in Canadian Arctic and Greenlandic waters, the narwhal is a uniquely specialized Arctic predator. In winter, it feeds on benthic prey, mostly flatfish, at depths of up to 1500 m under dense pack ice.

Narwhals have been harvested for over a thousand years by Inuit people in northern Canada and Greenland for meat and ivory, and a regulated subsistence hunt continues. Populations appear stable, but the narwhal is particularly vulnerable to climate change due to a narrow geographical range and specialized diet.

Taxonomy and etymology

Illustration of narwhal and its closest living relative the beluga

The narwhal was one of the many species originally described by Linnaeus in his Systema Naturae. Its name is derived from the Old Norse word nár, meaning "corpse", in reference to the animal's greyish, mottled pigmentation, like that of a drowned sailor and its summer-time habit of lying still at or near the surface of the sea (called "logging"). The scientific name, Monodon monoceros, is derived from the Greek: "one-tooth one-horn".

The narwhal is most closely related to the beluga whale. Together, these two species comprise the only extant members of the family Monodontidae, sometimes referred to as the "white whales". The Monodontidae are distinguished by medium size (at around 4 m (13 ft) in length), forehead melons, short snouts, and the absence of a true dorsal fin. The white whales, dolphins (Delphinidae) and porpoises (Phocoenidae) together comprise the superfamily Delphinoidea, which are of likely monophyletic origin. Genetic evidence suggests the porpoises are more closely related to the white whales, and that these two families constitute a separate clade which diverged from the Delphinoidea within the past 11 million years. Fossil evidence shows that ancient white whales lived in tropical waters. They may have migrated to Arctic and sub-Arctic waters in response to changes in the marine food chain during the Pliocene.

Description

Complete skeleton at the Zoological Museum of the Zoological Institute of the Russian Academy of Sciences

Narwhals are medium-sized whales, being around the same size as a beluga whale. Total length in both sexes, excluding the tusk of the male, can range from 3.95 to 5.5 m (13 to 18 ft). Males, at an average length of 4.1 m (13 ft 5 in), are slightly larger than females, at an average of 3.5 m (11 ft 6 in). Typical adult body weight ranges from 800 to 1,600 kg (1,800 to 3,500 lb). Males attain sexual maturity at 11 to 13 years of age, when they are 3.9 m (12 ft 10 in) long, and females attain maturity at 5 to 8 years old, when they are 3.4 m (11 ft 2 in) long. The pigmentation of the narwhal is a mottled pattern, with blackish-brown markings over a white background. They are darkest when born and become whiter with age; white patches develop on the navel and genital slit at sexual maturity. Old males may be almost pure white. Narwhals do not have a dorsal fin, possibly an evolutionary adaptation to swimming easily under ice. Its neck vertebrae are jointed, like those of land mammals, instead of being fused together. Both these characteristics are shared by the beluga whale. The tail flukes of female narwhals have front edges that are swept back, and those of males have front edges that are more concave and lack a sweep-back. This is thought to be an adaptation for reducing drag caused by the tusk.

Tusk

This narwhal skull has double tusks, a rare trait in narwhals. Usually, males have a single long tusk, the canine on the left side of the upper jaw. (Zoologisches Museum in Hamburg)

The most conspicuous characteristic of the male narwhal is its single extremely long tusk, a canine tooth that projects from the left side of the upper jaw, through the lip and forms a left-handed helix. The tusk grows throughout life, reaching lengths from 1.5 to 3.1 m (4 ft 11 in to 10 ft 2 in). The tusk is hollow and weighs around 10 kg (22 lb). About one in 500 males has two tusks, which occurs when the right canine, normally small and less straight, also grows out through the lip. Females may grow tusks sometimes; only about 15 percent of females have a tusk and female tusks are smaller than those of males, with a less noticeable spiral. Females may produce a second tusk, but there is only a single recorded case. The tusks are surrounded posteriorly, ventrally, and laterally by several small teeth which vary in morphology and histology. These teeth are vestigial and never erupt, and the narwhal's mouth usually appears toothless; some narwhals have a second, small tooth.

Biology considers the tusk a secondary sexual characteristic, similar to the mane of a lion or the tail feathers of a peacock. Charles Darwin discussed and defended this hypothesis at length in The Descent of Man, and Selection in Relation to Sex (1871). It may help determine social rank, maintain dominance hierarchies, or help young males develop skills necessary for performance in adult sexual roles. Narwhals have rarely been observed using their tusk for fighting, other aggressive behaviour or for breaking sea ice in their Arctic habitat. The tusk is a highly innervated sensory organ, as scientists established in the early years of the 21st century after many centuries of myth and fiction ascribing it other roles, ranging from magical to weaponry. There is at least one recorded case of a tusk being used against another species. A broken tusk was found embedded in the melon of a beluga, suggesting a fight.

Distribution

Narwhals in the Creswell Bay (at Somerset Island)

The narwhal is found predominantly in the Atlantic and Russian areas of the Arctic Ocean. Individuals are commonly recorded in the northern part of Hudson Bay, Hudson Strait, Baffin Bay; off the east coast of Greenland; and in a strip running east from the northern end of Greenland round to eastern Russia (170° East). Land in this strip includes Svalbard, Franz Joseph Land, and Severnaya Zemlya. The northernmost sightings of narwhal have occurred north of Franz Joseph Land, at about 85° North latitude. Most of the world's narwhals are concentrated in the fjords and inlets of Northern Canada and western Greenland. They are able to survive in depths of up to 1,500 m (4,900 ft) below sea level.

Migration

Narwhals are a migratory species. As spring comes, these leads open up into channels and the narwhals return to the coastal bays.

Narwhals exhibit seasonal migrations, with a high fidelity of return to preferred, ice-free summering grounds, usually in shallow waters. In summer months, they move closer to coasts, usually in pods of 10–100. In the winter, they move to offshore, deeper waters under thick pack ice, surfacing in narrow fissures in the sea ice, or leads. Narwhals from Canada and West Greenland winter regularly in the pack ice of Davis Strait and Baffin Bay along the continental slope with less than 5% open water and high densities of Greenland halibut. Feeding in the winter accounts for a much larger portion of narwhal energy intake than in the summer.

Behaviour

File:Narwhals breach.jpg

Narwhals "tusking"

Narwhals normally congregate in groups of about five to ten individuals, sometimes up to 20 outside the summer. Groups may be "nurseries" with only females and young or can contain only post-dispersal juveniles or adult males ("bulls"), but mixed groups can occur at any time of the year. In the summer, several groups come together, forming larger aggregations. Such aggregations can contain from 500 to over 1000 individuals. At times, bull narwhals rub their tusks together, a behaviour known as "tusking". This behaviour is thought to maintain social dominance hierarchies or maintenance of the tusk as a sensitive sensory organ.

Diet

Narwhals have a relatively restricted and specialized diet. Their prey is predominantly composed of Greenland halibut, polar and Arctic cod, cuttlefish, shrimp and armhook squid. Additional items found in stomachs have included wolffish, capelin, skate eggs and sometimes rocks, accidentally ingested when whales feed near the bottom. Due to the lack of well-developed dentition in the mouth, narwhals are believed to feed by swimming towards prey until it is within close range and then sucking it with considerable force into the mouth. It is thought that the beaked whales, who have similarly reduced dentition, also suck up their prey.

Narwhals have a very intense summer feeding society. One study published in the Canadian Journal of Zoology tested 73 individual narwhals, of different age and gender, to see what they ate. The individuals were from the Pond Inlet and had the stomach contents tested from June 1978 until September 1979. The study found in 1978 that the Arctic cod (Boreogadus saida) made up about 51% of the diet of the narwhals, with the next most common animal being the Greenland halibut (Reinhardtius hippoglossoides), consisting of 37% of the weight of their diet. A year later, the percentages of both animals in the diet of narwhals had changed. Arctic cod represented 57%, and Greenland halibut 29% in 1979. The deep-water fish - halibut, redfish (Sebastes marinus), and polar cod (Arctogadus glacialis) - are found in the diet of the males, which means that the narwhals can dive deeper than 500 m (1,600 ft) below sea level. The study found that the dietary needs of the narwhal did not differ among genders or ages.

Diving

Upside-down swimming behaviour of narwhals

Narwhal tail fluke

Narwhals can perform deep dives. When in their wintering waters, the narwhals make some of the deepest dives ever recorded for a marine mammal, diving to at least 800 metres (2,600 feet) over 15 times per day, with many dives reaching 1,500 metres (4,900 feet). Dives to these depths last around 25 minutes, including the time spent at the bottom and the transit down and back from the surface.

Communication

As with most toothed whales, narwhals use sound to navigate their environment and hunt for food. "Clicks", "whistles" and "knocks", may be created via air between chambers near the blow-hole, and reflected off the sloping front of the skull. These sounds are then focused by the animal's melon, which can be controlled by musculature. "Click trains" are produced both for echo-location of prey, and for locating obstacles at short distances. It is possible that individual "bangs" are capable of disorienting or incapacitating prey, making them easier to hunt, but this has not been verified. The whistles of a narwhal are rarely heard, especially compared to the beluga. Other sounds produced by narwhals include trumpeting and squeaking door sounds.

Breeding and early life

Females start bearing calves at six to eight years of age. Adult narwhals mate in April or May when they are in the offshore pack ice. Gestation lasts for 14 months and calves are born between June and August the following year. As with most marine mammals, only a single young is born each time. Newborn calves average 1.6 metres in length and are dark grey. The newborn calves begin their lives with a thin layer of blubber which is then thickened as they nurse their mother’s milk which is rich in fat. Calves are dependent on milk for around 20 months. This long lactation period gives calves time to learn the skills they need for survival. Mothers and calves stay close and when travelling, the calf stays by its mother's back for assistance in swimming.

Life span and mortality

A polar bear scavenging a narwhal carcass

Normally, narwhals can live up to at least 50 years. Although almost all modern predation of narwhals is by humans, a few natural predators also attack them on occasion. The primary natural predators are polar bears, who attempt to swipe narwhals at breathing holes and mainly target young whales, however, a pod of killer whales (orcas) can overwhelm a single narwhal. Greenland sharks and walruses may take a few small young or weak and wounded adults, though this is likely quite rare. When it comes to escaping predators such as orcas, narwhals typically choose prolonged submergence to hide under the ice rather than relying on speed.

Mortality often occurs when the narwhals suffocate after they fail to leave before the surface of the Arctic waters freeze over in the late autumn. Open water is formed in ice-covered water by fracturing events induced by strong winds, but when these conditions are absent ice can quickly form. This correlates with the observations that the last major entrapment events occurred when there was little to no wind observed in the area. Since narwhals are mammals they need air to breathe, so when open water is no longer accessible and the ice is too thick for them to break through, they can drown. Maximum aerobic swimming distance between breathing holes in ice is less than 1,450 m which limits the use of foraging grounds and these holes must be at least 0.5 m wide to allow an adult whale to breathe. The events can trap groups as large as 600 individuals. Most entrapment events occur in narwhal wintering areas such as Disko Bay and the largest entrapment event occurred in 1915 in West Greenland where over 1,000 narwhals were trapped under the ice. Despite the decreases in sea ice cover, there were several large cases of sea ice entrapment in 2008–2010 in the winter close to known summering grounds, two of which were locations where there had been no previous cases documented. This suggests later departure dates from summering grounds, which were recorded to be moving toward late autumn or even winter. Sites surrounding Greenland experiences advection of sea ice from surrounding regions by wind and currents, which increased the variability of when sea ice concentration reached certain thresholds. Also, due to strong site fidelity, changes in weather and ice conditions are not always associated with narwhal movement toward open water and therefore more data is needed to determine how vulnerable narwhals are to future sea ice changes. Starvation can also threaten their lives, especially in young whales.

Conservation issues

Narwhals are one of many mammals that are being threatened by human actions. The world population of narwhals is currently estimated to be around 75,000. They are considered to be near threatened and several sub-populations have evidence of decline. In an effort to support conservation, the European Union established an import ban on tusks. While there are many countries that have not only established these bans, they already have quotas on catches in place, which will be important also in newly opening areas caused by decreasing sea ice cover. Narwhals that have been brought into captivity tend to die of natural causes.

Male narwhal captured and satellite tagged

Inuit people, who call a tusked narwhal qilalugaq tugaalik, are allowed to hunt this whale species legally for subsistence. Narwhal has been extensively hunted the same way as other sea mammals, such as seals and whales, for its large quantities of fat which constituted one of the most important resources of the native people living in Arctic regions. Almost all parts of the narwhal, meat, skin, blubber and organs are consumed. Mattak, the name for raw skin and blubber, is considered a delicacy, and the bones are used for tools and art. The skin is an important source of vitamin C which is otherwise difficult to obtain. In some places in Greenland, such as Qaanaaq, traditional hunting methods are used, and whales are harpooned from handmade kayaks. In other parts of Greenland and Northern Canada, high-speed boats and hunting rifles are used.

During growth, the narwhal accumulates metals in its internal structures. One study found that many metals are low in abundance in the blubber of narwhals, and high in organs such as the liver and the kidney. Zinc and cadmium are found in higher densities in the kidney than the liver, and lead, copper and mercury, were found to be the opposite. Certain types of metals were correlated with size and sex. During growth, it was found that mercury accumulated in the liver, kidney, muscle and blubber, and that cadmium settled in the blubber.

Narwhals have been found to be one of the most vulnerable Arctic marine mammals to climate change. One of the aspects that make narwhals vulnerable to climate change is the altering sea ice coverage in their environment, especially in their northern wintering grounds such as the Baffin Bay and Davis Strait regions. Satellite data collected from these areas shows the amount of sea ice has been markedly reduced. Narwhals' ranges for foraging are believed to be patterns developed early in their life which increase their ability to gain necessary food resources during winter stages. This strategy focuses on strong site fidelity rather than individual level responses to local prey distribution and this results in focal foraging areas during the winter. As such, despite changing conditions narwhals will continue returning to the same areas during migration. Despite its vulnerability to sea ice change, the narwhal has some flexibility when it comes to sea ice and habitat selection. It evolved in the late Pliocene, and so is moderately accustomed to periods of glaciation and environmental variability.

An indirect danger for narwhals associated with changes in sea ice is the increased exposure in open water. In 2002 there was an increase in narwhal catches by hunters in Siorapaluk that did not appear to be associated with increased effort, implying that climate change may be making the narwhal more vulnerable to harvesting. Scientists urge assessment of population numbers and the assignment of sustainable quotas for stocks of as well as the collaboration of management agreements to ensure local acceptance. Seismic surveys associated with oil exploration have also been noted to disrupt normal migration patterns which may also be associated with increased sea ice entrapment.

Cultural depictions

The head of a lance made from a Narwhal tusk with a meteorite iron blade

In legend

In Inuit legend, the narwhal's tusk was created when a woman with a harpoon rope tied around her waist was dragged into the ocean after the harpoon had struck a large narwhal. She was transformed into a narwhal, and her hair, which she was wearing in a twisted knot, became the characteristic spiral narwhal tusk.

Some medieval Europeans believed narwhal tusks to be the horns from the legendary unicorn. As these horns were considered to have magic powers, such as the ability to cure poison and melancholia, Vikings and other northern traders were able to sell them for many times their weight in gold. The tusks were used to make cups that were thought to negate any poison that may have been slipped into the drink. During the 16th century, Queen Elizabeth received a carved and bejewelled narwhal tusk for £10,000—the cost of a castle (approximately £1.5–2.5 million in 2007, using the retail price index). The tusks were staples of the cabinet of curiosities. The truth of the tusk's origin developed gradually during the Age of Exploration, as explorers and naturalists began to visit Arctic regions themselves. In 1555, Olaus Magnus published a drawing of a fish-like creature with a horn on its forehead, correctly identifying it as a "Narwal".

In literature and art

Image of narwhal from Brehms Tierleben (1864–1869)

The narwhal was one of two possible explanations of the giant sea phenomenon written by Jules Verne in his 1870 novel Twenty Thousand Leagues Under the Sea. Verne thought that it would be unlikely that there was such a gigantic narwhal in existence. The size of the narwhal, or "unicorn of the see", as found by Verne, would have been 18 m (60 ft). For the narwhal to have caused the phenomenon, Verne stated that you would have to increase its size by five or ten times, multiply its strength by the same amount, and then the narwhal would have possibly been able to cause the phenomenon at sea.

Herman Melville wrote a section on the narwhal (written as "narwhale") in his 1851 novel Moby Dick, in which he claims a narwhal tusk hung for "a long period" in Windsor Castle after Sir Martin Frobisher had given it to Queen Elizabeth. Another claim made by him was that the Danish kings made their thrones from narwhal tusks.

In the book Northwest Passage written by Matthew James, based on the song by Stan Rogers, there is a tale of the discovery of the Northwest Passage. In the story, James stated, that as the ships captained by John Franklin travelled through the islands near King William Island, their sailors would have likely seen narwhals and walruses swimming about, between the islands and the ice.

In 2013, Canadian artist Harley Valentine created the sculpture North Pole, a gold-polished, lost wax bronze cast of a seven foot, 100-year old narwhal tusk thought to have come from Grise Fiord in the Canadian Arctic. Valentine claimed that the narwhal tusk is a "mammalian weather station", which helps narwhals to detect atmospheric changes.

Further reading

• M. P. Heide-Jorgensen. "Narwhal", in Encyclopedia of Marine Mammals, Perrin, Wursig and Thewissen eds. ISBN 0-12-551340-2
• Groc, Isabelle. "Hunt for the sea unicorn", New Scientist feature article, Issue 2956, 15 February 2014 [1]

External links

• Biology and ecology of narwhals, NOAA
• Narwhal FAQ
• Images and information about Narwhal Whales
• Narwhal general information
• Narwhal info
• National Geographic Gallery