by Whit Gibbons

September 2, 2012

Q: I recently saw an ABC News commentary where people were watching narwhals somewhere in the Arctic. They have a long, pointed horn that looks like a spear. What exactly are narwhals? What do ecologists know about these intriguing creatures?

A: Narwhals are a sort of marine unicorn of the Arctic Ocean. Males of the species have a long, protruding tusk (up to 10 feet!) that develops from the single, left upper jaw tooth. I have seen drawings of male narwhals engaged in what looked like fighting, and some scientists have suggested the horns are used in male-male combat. I am not aware of any definitive study confirming that the tusks are used for fighting rather than just for display. However, reports of tusk injuries to adult males suggest that combat may sometimes occur.

Whatever the case, since males have the tusks and females do not, they are presumably used in some activity that males do different from the opposite sex. Mating with females seems a likely guess. Perhaps they use them to intimidate other males or simply to impress females. To my mind, narwhals are not as charming as their closest relative, the beluga whale, but they come close.

According to "Walker's Mammals of the World" by R. M. Nowak (1999, Johns Hopkins University Press, Baltimore), which remains the best overall scientific authority on mammals, belugas and narwhals are separate genera, each with a single species. They are the only two species in a family of whales know as the Monodontidae, which means "one tooth." The narwhal was described to science first, in 1758 by Linnaeus, and the single tusk, a long, modified tooth, would clearly have been the most noticeable feature, although narwhals typically have another, smaller tooth as well.

Both beluga whales and narwhals inhabit some of the coldest waters on the planet and migrate long distances. Narwhals have the most northerly geographic range of any mammal, almost entirely above the Arctic Circle, and rarely travel farther south than 70 degrees north latitude. One measure of the frigid conditions narwhals live under is that one-third of their body weight is blubber, which serves as an insulator and a source of energy. Despite the contention by some folks that global warming is not really happening, if the ice cover maps I have seen are any indication, the character of the Arctic habitat where narwhals live is changing dramatically. Diminishing ice and seasonal temperature changes could have an impact on narwhal migration and feeding patterns. What the final outcome would be for the species is uncertain.

The restriction of narwhals to an ocean habitat in a climate that is almost uninhabitable by humans is one reason for limited scientific knowledge of the behavior and mating systems of these fascinating creatures. The knowledge that, on average, males are more than 15 feet long (not counting the bayonet protruding from the head), weigh over 3,500 pounds, and are larger than females has been determined from specimens that were killed. Baby narwhals are born during summer and are already five feet long and weigh 175 pounds. Not surprisingly, a mother narwhal, which averages less than a ton, produces a single offspring at a time. The gestation period is more than 15 months.

As if the surface in the Arctic seas isn't cold enough for narwhals, radiotelemetry studies have revealed that narwhals commonly dive to ocean depths of more than 800 feet. Aside from the sheer fun of swimming in ice cold ink-black water, their purpose is to feed on a variety of fish, squid, and crustaceans. Some narwhals can remain underwater for more than 15 minutes but like other mammals must eventually surface to breathe. The use of echolocation for navigation has not been verified in the species, but they are known to make several noises--whistles, clicks, groans--that could be used for orientation in the dark.

Narwhals are cool animals indeed. In fact, they are arguably the coolest animals in the world.

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