How Narwhals are like Peacocks
Recently, R. Schouweiler, a curious field notes reader, sent us some questions about narwhals, the tusk-bearing whales that inhabit the deeply frigid waters off of western Greenland. We forwarded the note to marine mammal biologist and narwhal expert, Kristin Laidre (research scientist at the University of Washington’s Polar Science Center), who we’ve featured in the field notes blog before.
Where and when do they calve? At what depth do the females give birth to their calves?
The breeding period for narwhals is in early spring (March-April) in the dense ice of their offshore wintering grounds (Baffin Bay, David Strait or East Greenland). The gestation period is about 14 months and they give birth to calves in late spring (May-June) during their northbound migration to the summering grounds. We do not know what specific depth females give birth to calves but my guess is it is relatively close to the surface as a newborn calf needs to breathe air relatively quickly and does not yet have the extreme diving capabilities of adult narwhals.
In addition to play and defense, is the elongated "tooth" of the male Narwhal used to spear their food sources, such as squid, halibut - a bottom fish (and one of my very favorite sea foods baked or grilled with a few thin slices of lemon) - or any other type of food source?
The narwhal is an odontocete or toothed whale, but unlike all other toothed whales it has no teeth in its mouth. Instead, the male develops a long straight tooth (or tusk) that protrudes 2-3 m out of the upper left jaw. The tooth grows in a counterclockwise spiral. The tusk is unique to male narwhals. Rarely a female will grow a tusk, or a narwhal will grow two tusks. For the most part, females lack tusks. Tusks exported from the Arctic, perhaps by the Vikings, reached Europe, the Mediterranean, and even the Far East as early as the Middle Ages and became the source of the unicorn myth. The tusks were sold without a good description of the animal from which they came and inspired a great deal of fantasy.
To some extent, the tusks still inspire fantasies, as many explanations have been proposed for the purpose of the tusk, including: breaking ice, sword-fighting, spearing fish for food, or for digging in the bottom the sea. In fact, none of these behaviors have ever been observed. While narwhals do frequently feed on fish (Greenland halibut) close to the sea floor, they do not spear them with the tusk but instead swallow them whole!
The scientific consensus is that the narwhal tusk is a sexual trait, much like the antlers of a stag, the mane of a lion or the feathers of a peacock. Males use the tusk to determine social rank and compete for females. During the summertime in the northern Canadian high Arctic bays and fjords (long narrow inlets), male narwhals can be seen carefully crossing their tusks at the surface. There is often a female between them. Such behavior might help maintain dominance hierarchies or help young males develop skills necessary for performance in adult sexual roles. The sexual selection theory was originally proposed by Charles Darwin in his book The Descent of Man, and Selection in Relation to Sex (1871).
Many thanks to Dr. Laidre for her thoughtful responses. Readers can find more narwhal information on a FAQ page on Kristin’s website: http://staff.washington.edu/klaidre/narwhalfaq.html
If you’re like me, you wonder how obviously smart, seemingly reasonable people end up spending serious time pursuing their life’s passion in the remote polar regions. Kristin offers some insight to the path that brought her to the world of narwhals, and the challenges and payoffs of her career choices, on NOAA’s Ocean Explorer website.
Wondering about polar research? Send us your questions and we'll get them answered. We may also send you some schwag!—Kip Rithner