Narwhals normally congregate in groups of about five to ten individuals. In the summer, several groups come together forming larger aggregations.
Narwhal is derived from the Old Norse word nár, meaning “corpse”, referring to the animal’s greyish, mottled pigmentation, like that of a drowned sailor. Narwhal are darkest when young becoming whiter with age.
The most conspicuous characteristic of the male narwhal is its single 2–3 meter (7–10 ft) long twisted tusk. It is an incisor tooth that projects from the left side of the upper jaw and forms a left-handed helix. The narwhal’s scientific name, Monodon monoceros, is derived from Greek “one-tooth one-horn.” The tusk can be up to 3 meters (9.8 ft) long—compared with a body length of 4–5 meters (13–16 ft)—and weigh up to 10 kilograms (22 lb). About one in 500 males has two tusks, which occurs when the right incisor, normally small, also grows out. A female narwhal may also produce a tusk, but this occurs rarely, and there is a single recorded case of a female with dual tusks.
This behavior is thought to maintain social dominance hierarchies.
At times, male narwhals rub their tusks together in an activity called “tusking.” The reason for this behavior is unknown; it may be to “scratch an itch,” (the base of the tusk is usually infested with lice); or tusk crossing may be a friendly greeting. The most broadly accepted theory for the role of the tusk is as a secondary sexual characteristic, similar to the mane of a lion or the tail feathers of a peacock. 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 or other aggressive behavior or for breaking sea ice in their Arctic habitat.
Narwhal usually proceed at a leisurely pace, slowly breathing and rolling, but are remarkably quick when they feel threatened. Sometimes they travel in small family groups and communicate by means of a great variety of squeals, trills, whistles, and clicks.
Narwhals have a relatively restricted and specialized diet. Their prey is predominantly composed of Greenland halibut, polar and Arctic cod, shrimp and Gonatus squid. Additional items found in stomachs have included wolffish, capelin, skate eggs and sometimes rocks, accidentally ingested when whales feed near the bottom. How narwhal catch their prey is unknown. Some scientists believe narwhal stun their prey with sound as do dolphins .
Narwhal exhibit seasonal migrations with high fidelity of return to preferred ice-free summering grounds, usually in shallow waters. In the winter, they are found primarily in offshore, deeper waters under thick pack ice, surfacing in narrow fissures in the sea ice, or leads. Narwhal 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 and, as marine predators, they are unique in their successful exploitation of deep-water arctic ecosystems.Most notable of their adaptations is the ability to perform deep dives. When on their wintering grounds, the narwhals make some of the deepest dives ever recorded for a marine mammal, diving to at least 800 meters (2,400 feet) over 15 times per day with many dives reaching 1,500 meters (4,500 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. In the shallower summering grounds, narwhals dive to depths between 30 and 300 meters (90–900 feet).
The only predators of narwhals besides humans are polar bears and orcas. Inuit people are allowed to hunt this whale species legally for subsistence. The northern climate provides little nutrition in the form of vitamins which can only be obtained through the consumption of seal, whale, and walrus. Almost all parts of the narwhal, meat, skin, blubber and organs, are consumed. Mattak, the word for raw skin and blubber, is considered a delicacy, and the bones are used for tools and art. 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.
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 herself, and her hair, that 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 bejeweled narwhal tusk for £10,000—the cost of a castle (approximately £1.5—2.5 Million in 2007.
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”.