Wildlife Climatology The Expedition Peoples Of The North The Global Issues The "Making Of"

Wildlife

Climatology

The Expedition

Peoples Of The North

The Global Issues

The "Making Of"

A sword that defies the imagination -- the narwhal tusk

Isabelles Deslandesby Isabelle Deslandes, Ship's doctor

There is a mysterious whale that inhabits our Arctic sea – an extraordinary creature that could be mistaken for an aquatic version of the mythical unicorn. It is the narwhal.

 

What makes the narwhal so special? Its tusk.

The narwhal’s ivory tusk is hollow, slender and usually spirals in a counter-clockwise direction. This tusk is actually the gigantic extension of a transformed left upper canine that grows through the jaw. It can grow to 2 or 3 metres long and can weigh up to 10 kilograms. A single tusk is typically seen in adult males and continues to elongate during its lifetime. Some animals have been observed with two tusks, one on the right side, one on the left, but these are uncommon occurrences. In rare cases, some females have been observed with smaller, denser, horn-like structures in lieu of the tusk of the male.

NarwhalThirteen Northern Native communities are permitted to hunt the narwhal. The ivory harvested from the tusks represents a profitable export. Prices for one tusk can reach $3,000 US! (Such high prices can be fetched in Japan, where the ivory is believed to have aphrodisiac properties.) Tusks are also carved by local sculptors.

But what do the narwhal whales use their tusks for?

Several hypotheses have been offered to explain the purpose of this intriguing structure. The first hypothesis was that the narwhal useds the tusk as a sword to harpoon pelagic fish. An attractive idea until one poses the question, then how does the whale eat the fish attached to the tip of its tusk? The second hypothesis was that the tusks are used to scratch the ocean floor to harvest bottom-dwelling organisms. Another idea, which pleased quite an audience at the time, was that the tusk function as an ear. The single hypothesis currently accepted by scientists is that the tusk represents a secondary sexual characteristic used by males to indicate social ranking. Males use their tusks in non-aggressive encounters between each other by crossing them repetitively in unique patterns. It is suggested that this behaviour attracts receptive females during mating season.



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