Narwhal

**The** **narwhal** is the unicorn of the sea, a pale-colored porpoise found in Arctic coastal waters and rivers. These legendary animals have two teeth. In males, the more prominent tooth grows into a swordlike, spiral tusk up to 8.8 feet (2.7 meters) long. The ivory tusk tooth grows right through the narwhal's upper lip. Scientists are not certain of the tusk's purpose, but some believe it is prominent in mating rituals, perhaps used to impress females or to battle rival suitors. Females sometimes grow a small tusk of their own, but it does not become as prominent as the male's. The tusk is an innervated sensory organ with millions of patent nerve endings connecting seawater stimuli in the external ocean environment with the brain. The rubbing of tusks together which males engage in is now hypothesized to communicate information about the water each has traveled through rather than to represent the previously assumed “male-to-male rivalry“. Narwhals have only occasionally been observed using the tusk for aggressive behavior.

### **Migration**

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. As spring comes, these leads open up into channels and the narwhals return to the coastal bays. 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.

## Behavior

Narwhals normally congregate in groups of about five to ten, and 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 year. In the summer, several groups come together, forming larger aggregations which can contain from 500 to over 1000 individuals. At times, a bull narwhal may rub its tusk with another bull, a display known as "tusking" and thought to maintain social dominance hierarchies. However, this behavior may exhibit tusk use as a sensory and communication organ for sharing information about water chemistry sensed in tusk microchannels.

## Taxonomy and Etymology

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". Narwhals are related to bottle nose dolphins, belugas, harbor porpoises, and orcas. Like some other porpoises, they travel in groups and feed on fish, shrimp, squid, and other aquatic fare. They are often sighted swimming in groups of 15 to 20, but gatherings of hundreds—or even several thousand—narwhals have been reported. Sometimes these groups become trapped by shifting pack ice and fall victim to Inuit hunters, polar bears, or walruses.

## Conservation Issues

Inuit people hunt the narwhal for their long tusks and their skin, an important source of vitamin C in the traditional Arctic diet.

## Gallery

Narwhals FightingNarwhal Tusk2 Tusked NarwhalWild Kratts