Narwhal

Name and taxonomy

Carl Linnaeus named the narwhal in 1758 in Systema Naturae. The scientific name comes from Greek and means one tooth, one horn. The common name comes from the Old Norse word nárhval, which means corpse whale. The Norse probably chose it for the grey, blotched skin and for the way the animal lies still at the surface. GBIF lists older English names such as sea unicorn, horned whale and unicorn whale.

The narwhal is the only species in the genus Monodon. It belongs to the family Monodontidae with one other living species, the beluga whale. Both have a large melon on the forehead, a short snout and no true dorsal fin. The two species can interbreed, and a skull found in West Greenland around 1990 proved to be a hybrid. A DNA study confirmed the narluga in 2019.

Evolution and relatives

Genetic studies place the narwhal and beluga closest to the porpoises. That group split from the other dolphins about 11 million years ago. A 2020 study put the split between narwhal and beluga at about 4.98 million years ago. A fossil from the early Pliocene of Italy, Casatia thermophila, may be an early relative. Other extinct genera come from the Pliocene of the United States.

The fossils show that early monodontids lived in warm seas. They probably moved north as the ocean food web changed, and their descendants became Arctic specialists. The beluga today shares the narwhal's jointed neck, low dorsal ridge and blunt head.

Appearance

The narwhal has a stocky body, a short blunt snout and small flippers with upturned tips. Adults measure 3 to 5.5 metres long and weigh 800 to 1,600 kg. Males are about 70 centimetres longer than females and more than 75 percent heavier. A ridge runs along the back where other whales have a fin. The neck bones are not fused, so the head can turn.

A calf is born light grey. White patches spread with age, and an adult is mottled dark grey or brown over a white belly. Very old animals, and old males above all, can be almost white. A layer of blubber 50 to 100 millimetres thick makes up about a third of the body mass. The tail flukes differ by sex, and the male's flukes bend inwards, perhaps to offset the drag of the tusk.

The tusk is the left canine tooth, and it grows out through the lip when a male is two to three years old. It spirals to the left, grows throughout life and reaches 1.5 to 3 metres. The tusk is hollow, and the heaviest weigh 7.45 kilograms. A few males grow two tusks, and a few females grow a short one. Apart from the tusks, the narwhal has only a pair of tiny useless teeth in the upper jaw.

Habitat and range

The narwhal is the most northerly whale. It lives in the Atlantic and Russian parts of the Arctic Ocean, mostly between 70 and 80 degrees north. The main areas are the Canadian Arctic Archipelago, Baffin Bay, Hudson Bay, and the coasts of Greenland. A thinner band runs east past Svalbard and Franz Josef Land to Severnaya Zemlya. The northernmost record is about 85 degrees north, beyond Franz Josef Land. Strays have reached Newfoundland, the Netherlands, Britain and Japan.

Narwhals migrate with the seasons and return to the same summer grounds year after year. In summer they gather in shallow coastal bays and fjords, in pods of 10 to 100. In autumn the Baffin Bay animals travel about 1,700 kilometres south to the Davis Strait. They spend the winter under dense pack ice with less than 5 percent open water, where Greenland halibut are plentiful. They breathe through cracks and leads in the ice until spring opens the channels again.

Diet and hunting

The narwhal eats a narrow range of prey. A study of 73 stomachs found Arctic cod most often, then Greenland halibut and large amounts of armhook squid. Males also ate polar cod and redfish, which live below 500 metres. Wolffish, capelin, shrimp, skate eggs and even stones turn up in stomachs as well. Winter is the main feeding season, when the whales take flatfish from the sea floor under the ice. In summer many stomachs are empty.

With no working teeth, the narwhal is thought to suck prey into its mouth at close range. Drone film from Tremblay Sound in Nunavut in 2016 showed narwhals tapping Arctic cod with the tusk to stun them. The tusk cannot be a main feeding tool, because most females lack one and they live longer than males. The hunting dives are long and deep. In winter a narwhal dives past 800 metres more than 15 times a day, and dives last up to 25 minutes.

Behaviour and social life

Narwhals live in small groups of three to eight. A group may hold only mothers and calves, only young animals, or only bulls, and mixed groups also occur. In summer many groups merge into herds of 500 to more than 1,000. After the migration the herds break up into the old small pods. Scientists do not yet know whether pod members are related.

Males rub their tusks together, a habit called tusking. Some biologists see it as a fight for rank, and others think it cleans the tusk. Narwhals lie still at the surface, a behaviour called logging, and they sink away quietly when a ship comes near. That habit and their colour make them hard to study.

Sometimes a pod stays too long in a bay and the sea freezes around it. The whales then share one shrinking hole and can starve or drown. Trapped animals have been seen taking care not to hurt each other with their tusks. About 1,000 carcasses were found after such traps in the winter of 1914 to 1915, many in Disko Bay.

Communication and senses

Like other toothed whales, the narwhal finds its way and its food by sound. It makes clicks, whistles and knocks with air moved between chambers near the blowhole. The melon on the forehead focuses the clicks, and the echoes reveal prey and ice at short range. Whistles and throbs carry messages between pod members. Calls from one pod sound more alike than calls from different pods, so each group may have its own dialect. Other sounds include trumpets and a noise like a squeaking door.

The tusk is also a sense organ. It holds about ten million nerve endings and can register the temperature and salt content of the water. The nerves may also sense pressure and the particles in the water. The narwhal's calls resemble the beluga's, but the clicks differ in pitch and rate.

Reproduction and life cycle

Mating takes place in the offshore ice between March and May. A dominant male is thought to mate with several females. Females are probably choosing mates by the size of the tusk, though the evidence is still thin. Gestation lasts about 14 to 15 months, and most calves arrive in July and August of the next year. A female gives birth to one calf, and twins are rare.

A newborn is about 1.5 metres long and weighs about 80 kilograms. It is born tail first with a thin layer of blubber and swims at once. The calf drinks rich milk for about 20 months, and the blubber thickens as it grows. A female calves only every two to three years because the calf nurses so long. Females mature at six to nine years, and males at 12 to 20 years.

Narwhals live about 50 years by the count of layers in the jaw bone. Dating of the eye lens suggests females can reach about 115 years and males 84. Females go through menopause and live for decades after their last calf. Older females may help protect the calves in the pod.

Predators and threats

Orcas hunt narwhals, and pods have been seen surrounding and killing a whole group. Polar bears wait at breathing holes to catch young whales. Walruses and polar bears also eat narwhals trapped in the ice. Narwhal remains have turned up in Greenland sharks. A chased pod bunches together and slips under the ice floes rather than trying to outrun the orcas.

Ice is both shelter and danger. Breathing holes can lie 1,450 metres apart and must be at least half a metre wide. Entrapments were recorded in new places between 2008 and 2010, which suggests later departures from the summer grounds. Bacteria of the genus Brucella, whale lice, morbillivirus and a herpesvirus have all been found in narwhals.

Population and conservation

The IUCN lists the narwhal as Least Concern. The 2017 estimate was 170,000 animals, with 123,000 of them mature. Baffin Bay holds around 140,000, and northern Hudson Bay about 12,500. Counts include 49,000 near Somerset Island, 35,000 in Admiralty Inlet and 17,000 in eastern Baffin Bay. Only about 800 live off Svalbard. Older assessments called the species Near Threatened or Data Deficient because the counts were poor.

CITES lists the narwhal in Appendix II, which controls the trade in tusks. The United States banned imports in 1972 under the Marine Mammal Protection Act. The European Union bans narwhal ivory, and in 2025 the United Kingdom added the tusk to its Ivory Act. Canada's COSEWIC lists the species as Special Concern. Scientists rank the narwhal among the Arctic mammals most at risk from sea ice loss. It returns to the same wintering grounds whatever the ice does.

Relationship with humans

Inuit in Canada and Greenland have hunted narwhals for thousands of years. They eat the meat, the organs and above all muktuk, the raw skin with its blubber. The skin supplies vitamin C, which is hard to find in the Arctic. The oil once lit and heated homes, the sinews served as thread, and the tusk tipped harpoons. In Qaanaaq hunters still harpoon whales from kayaks, while elsewhere they use motorboats and rifles.

About 1,000 narwhals are killed each year, 600 in Canada and 400 in Greenland. A 2013 paper put the gross income from one whale at about 6,542 Canadian dollars. The hunts run on subsidies and continue for tradition more than profit. Narwhals build up mercury, cadmium and other metals in the liver and kidneys. Seismic surveys for oil disturb their migrations, and ships cross their routes. No narwhal has lived more than four months in captivity, so no aquarium keeps one.

In culture and myth

In Inuit legend, a woman was dragged into the sea when a harpoon line around her waist caught a great narwhal. She turned into a narwhal, and her twisted knot of hair became the spiral tusk. In Norse tradition the animal was the corpse whale, and Vikings and the Greenland Norse began the tusk trade. It is not clear whether they hunted the whales or gathered tusks from orca kills.

In medieval Europe the tusk passed as the horn of the unicorn. Apothecaries sold chips and powder as an antidote to poison and a cure for measles, rubella and plague. A whole horn was said to clean water and to show up poison in a drink. Tusks were given as state gifts and could sell for many times their weight in gold. Elizabeth I received one from Martin Frobisher said to be worth 10,000 pounds, and Ivan the Terrible kept a jewelled tusk on his deathbed. The throne of the Danish kings is built from narwhal tusk.

The rise of science in the late 17th century ended the unicorn trade. The tapestry cycle The Lady and the Unicorn shows the horn as artists imagined it. Today the narwhal is a favourite of children's toys, cartoons and internet jokes, and the nickname unicorn of the sea has stuck.