The narwhal is a stocky cetacean with a relatively blunt snout, a large melon, and a shallow ridge in place of a dorsal fin.

Specially adapted slow-twitch muscles, along with the jointed neck vertebrae and shallow dorsal ridge allow for easy movement through the Arctic environment, where the narwhal spends extended periods at great depths.

The narwhal's geographic range overlaps with that of the similarly built and closely related beluga whale, and the animals are known to interbreed.

The population is threatened by the effects of climate change, such as reduction in ice cover and human activities such as pollution and hunting.

[5] The word "narwhal" comes from the Old Norse nárhval, meaning 'corpse-whale', which possibly refers to the animal's grey, mottled skin and its habit of remaining motionless when at the water's surface, a behaviour known as "logging" that usually happens in the summer.

[citation needed] Monodontids are distinguished by their pronounced melons (acoustic sensory organs), short snouts and the absence of a true dorsal fin.

It had features midway between a narwhal and a beluga, indicating that the remains belonged to a hybrid between the two species (a 'narluga');[11] this was confirmed by a 2019 DNA analysis.

[11][13] Results of a genetic study reveal that porpoises and monodontids are closely related, forming a separate clade which diverged from other dolphins about 11 million years ago (mya).

[15] A later phylogenetic study conducted in 2020 suggested that the narwhal split from the beluga whale around 4.98 mya, based on data from mitochondrial DNA.

Delphinapterus leucas (Beluga whale) The narwhal has a robust body with a short, blunt snout, small upcurved flippers, and convex to concave tail flukes.

[6][21][29] The most conspicuous trait of male narwhals is a long, spiralled tusk, which is a canine tooth that projects from the left side of the upper jaw.

[36] The tusk is also a highly innervated sensory organ with millions of nerve endings, allowing the narwhal to sense temperature variability in its surroundings.

[37][38] According to Dr. Martin Nweeia, male narwhals may rid themselves of encrustations on their tusks by rubbing them together, as opposed to posturing displays of aggressive male-to-male rivalry.

[37][38] Drone footage from August 2016 in Tremblay Sound, Nunavut, revealed that narwhals used their tusks to tap and stun small Arctic cod, making them easier to catch for feeding.

[36][40] Alongside its tusk, the narwhal has a single pair of small vestigial teeth that reside in open tooth sockets in the upper jaw.

[45] Narwhals exhibit seasonal migration, with a high fidelity of return to preferred ice-free summering grounds, usually in shallow waters.

In the winter, they move to deeper waters offshore, under thick pack ice, surfacing in narrow fissures or in wider fractures known as leads.

In the northern wintering grounds, narwhals do not dive as deep as the southern population, in spite of greater water depths in these areas.

[56] A study of the stomach contents of 73 narwhals found Arctic cod (Boreogadus saida) to be the most commonly consumed prey, followed by Greenland halibut (Reinhardtius hippoglossoides).

Male specimens had a higher likelihood of showing two additional prey species within their stomach contents: polar cod (Arctogadus glacialis) and redfish (Sebastes marinus), both of which are found at depths of more than 500 m (1,600 ft).

[23][64] A 2024 study concluded that five species of toothed whale evolved menopause to acquire higher overall longevity, although their reproductive periods did not change.

[67][68] Sounds are reflected off the sloping front of the skull and focused by the animal's melon: a mass of fat which can be controlled through surrounding musculature.

Narwhals sometimes adjust the duration and pitch of their pulsed calls to maximise sound propagation in varying acoustic environments.

Due to their tendency of returning to the same areas, changes in weather and ice conditions are not always associated with narwhal movement toward open water.

[3] In the 1972 Marine Mammal Protection Act, the United States banned imports of products made from narwhal parts.

[45][84] In 2025 the United Kingdom protected narwhals under the Ivory Act, which forbids trade in teeth and tusks except for "artistic and cultural artifacts.

[91] It is thought that pollution in the ocean is the primary cause of bioaccumulation in marine mammals; this may lead to health problems for the narwhal population.

[93] Narwhals are one of the Arctic marine mammals most vulnerable to climate change due to sea ice decline,[47] especially in their northern wintering grounds such as the Baffin Bay and Davis Strait regions.

[94] It is thought that narwhals' foraging ranges reflect patterns they acquired early in life, which improves their capacity to obtain the food supplies they need for the winter.

This strategy focuses on strong site fidelity rather than individual-level responses to local prey distribution, resulting in focal foraging areas during the winter.