NARWHALS"Unicorn of the Sea"

(G1)


Scientific Classification
A narwhal as depicted in the zoological encyclopedia Brehms Tierleben, 1860.(G2)
A narwhal as depicted in the zoological encyclopedia Brehms Tierleben, 1860.(G2)


Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Suborder: Odontoceti
Family: Monodontidae
Genus: Monodon
Species: Monodon monoceros

The narwhal and the beluga whale are the only living species in the Monodontidae family, or the "white whales." Narwhals belong to the suborder of Odontoceti, meaning they have teeth such as dolphins or sperm whales, though one of its two teeth is actually the characteristic tusk jutting from their upper left jaw [3]. The name Monodon monoceros is Greek for "one-tooth one-horn," though this isn't technically true since they are in fact one in the same [3]. The name "narwhal" comes from the old Norse prefix "Nar," meaning "corpse," and "hval," or "whale." "Corpse whale" references their mottled gray skin color, similar to that of a drowned sailor [1].

Physiology


Narwhals are born gray, but as they age they develop a black and white mottled skin pattern on their dorsal side, along with a white underbelly [3]. Their shape is similar to a beluga whale, but more streamlined (i.e. less blubber/fat). This saves energy and helps maximize oxygen consumption [1]. They do not have a dorsal fin, but rather a dorsal ridge, for easier navigation under ice [2]. Males can reach a length of 16 feet and weigh up to 4,000 lbs, while females can be around 14 feet and up to 2,200 lbs [1]. Like other Odontoceti, the brain of a narwhal is only slightly smaller than that of a human - rendering them remarkably intelligent [2]. This is perhaps most apparent in terms of how they communicate, using a complex language of clicks and whistles called echolocation to detect underwater prey, navigate, and converse with one another.

(G3)

Their truly distinguishing factor, however, is the unique tooth-tusk. It protrudes through the lip up to 9 feet out of the upper left jaw in a counterclockwise spiral [1]. It is the only straight (non-curved) tusk in the world, and one of the only spiral teeth. The very makeup of the tooth is odd - structurally, it is inside-out. The surface is covered in millions of tiny holes, making it soft, flexible, and very sensitive. Dense enamel is found at its center [2]. In most cases, the tusk is a trait of only the male narwhals, but research suggests about 15% of females will grow a tusk as well, and some of both genders will grow a second! [2]

Mystery of the Tusk

Close-up of spiral tusk. Paul Nicklen/National Geographic/Getty Images (G4)
Close-up of spiral tusk. Paul Nicklen/National Geographic/Getty Images (G4)

To this day, the tusk's purpose remains a mystery. Historically, its purposes have been speculated to include breaking ice, dueling, spearing prey, or deep sea digging [1]. However, if this tool was essential for obtaining food, no narwhal would be without it (females included); and if it were necessary for defense, the females and young would be at a severe disadvantage. In reality, most females outlive their tusked male counterparts [4]. An intriguing new theory of Dr. Martin Nweeia of Harvard School of Dental Medicine is that the tusk acts as a sensor to detect temperature, water pressure and salinity [2]. This would be due to its sensitive, nerve-covered exterior. However, it still doesn't solve the issue of why females are largely without them. The most viable and widely accepted answer is that the tusks are simply a sexual characteristic used to determine social rank and impress females [4]. With this explanation, previously reported "sword fights," (which, if true, would be extremely painful for both parties) could be chalked up to gentle exercises in sexual dominance.


Population

A pod of narwhals supposedly "jousting" (G5)
A pod of narwhals supposedly "jousting" (G5)

Worldwide, there are about 80,000 narwhals. They travel in groups of around 20-30 at a time, unless in migration, in which case thousands may be swimming together [2]. Sexual maturity is reached between ages 6-9 and females give birth to a calf about every third year [1]. The breeding period takes place in early Spring under the dense ice of their wintering grounds. Gestation takes about 14 months, and they give birth in late Spring en route to their summering grounds [1]. No one is exactly sure of the average lifespan of a narwhal, but new research using the lens of an eye suggests they can live to be 115 years old. [5]





Habitat & Migration


Narwhals live in the fairly concentrated reaches of the Arctic Ocean off Canada, Baffin or Hudson Bay, the east and west coast of Greenland, and Eastern Russia. They are able to navigate through these icy regions with the help of pools of open water called polynyas. These channels act a sort of arctic oasis. [2]
An Arctic feeding ground, or polynya, at Lancaster Sound. Paul Nicklen/National Geographic/Getty Images (G6)
An Arctic feeding ground, or polynya, at Lancaster Sound. Paul Nicklen/National Geographic/Getty Images (G6)

Location of narwhal populations. Solid: frequent, striped: rare (G7)
Location of narwhal populations. Solid: frequent, striped: rare (G7)


Narwhals migrate seasonally. In winter, they inhabit deep offshore waters under thick pack ice. They have less than 5% of open water to work through, yet the halibut thrive, so they exploit the opportunity to feed [1]. During these winter months, Narwhals are thought to dive deeper than any marine mammal - plunging at least 2,625 feet over 15 times a day, and often even doubling that depth! [5] These amazing feats last for about 25 minutes before oxygen is required. As summer arrives, fissures begin to open routes for travel to shallow, ice-free waters by the coast.

Diet


Because narwhals feed far offshore and under thick layers of ice, no observations of narwhals feeding have ever been made. However, we do know that their diet changes seasonally, with the majority of the feast taking place in the darkness of winter. By opening their stomachs, research has found a very specialized menu of Greenland halibut, cod, shrimp, and Gonatus squid [1]. Rarely, various other small species can be found, but it's most likely accidental.


Threats

Inuit sealer Aron Aqqaluk Kristiansen from Greenland with a decapitated double-tusked narwhal. Nobody likes Aron. Nikolaj Svendsen/AFP/Getty Image(G8)
Inuit sealer Aron Aqqaluk Kristiansen from Greenland with a decapitated double-tusked narwhal. Nobody likes Aron. Nikolaj Svendsen/AFP/Getty Image(G8)

In the Middle Ages, Vikings exported Narwhal tusks to Europe, the Mediterranean, and the Far East under the vague pretense that they were unicorn horns. Superstitious foreigners often purchased them for ten times their weight in gold [1]. Today, a tusk can still be worth about $125 a foot, or even thousands for a double-tusk [2]. However, there are strict regulations on the hunting of Narwhals, and Inuits are only allowed to kill a certain number per year for food, in accordance to their tradition [2]. Yet often narwhals will be shot/harpooned only to sink to the bottom of the ocean, and go unreported. Killer whales, walruses, and polar bears pose a more natural threat. Recently, global warming is beginning to effect migratory trends; sometimes trapping narwhals beneath thicker ice layers, or allowing entry for these predators to sneak into their feeding grounds [5]. Due to all this, they are considered a nearly threatened species.







Information Sources

1. Laidre, Kristin L. "Narwhal FAQ." University of Washington. Web. 29 Nov 2011.
<http://staff.washington.edu/klaidre/narwhalfaq.html>
2. Lambert, Katie. "How Narwhals Work." How Stuff Works.Web. 29 Nov 2011.
<http://science.howstuffworks.com/environmental/life/zoology/marine-life/narwhal.htm>
3. "Narwhal Facts." Narwhal Tusk Discoveries. Web. 29 Nov 2011.
<http://www.narwhal.org/NarwhalFacts.html>
4. Scoresby, William. An Account of the Arctic Regions with a History and Description
of the Northern Whale-Fishery. Edinburgh: Archibald Constable and Co.,
1820. Print.
5. Heide-Jorgensen, M.P. "Narwhal." Encyclopedia of Marine Mammals. Perrin,
Wursig and Thewissen eds. ISBN 0-12-551340-2

Multimedia

Fig G1 http://www.youtube.com/watch?v=OQ1a9LhkIoQ&feature=player_embedded
Fig G2 http://upload.wikimedia.org/wikipedia/commons/5/57/Narwal_brehm.jpg
Fig G3 http://www.youtube.com/watch?v=iUXE6DRt6H0&feature=player_embedded
Fig G4 http://static.howstuffworks.com/gif/narwhal-close.jpg
Fig G5 http://upload.wikimedia.org/wikipedia/commons/5/5c/Narwhals_breach.jpg
Fig G6 http://1.bp.blogspot.com/_0C3gi-Ych0M/SPo5EAToA4I/AAAAAAAABDg/mY_CEr_yl6A/s400/narwhals.jpg
Fig G7 http://upload.wikimedia.org/wikipedia/commons/d/d5/Narwhal_distribution_map.png
Fig G8 http://static.howstuffworks.com/gif/narwhal-hunt.jpg