| MadSci Network: Zoology |
Hi Bryan,
I was able to find the answer to your question at the site http://www.uwsports.ycg.com/magazine/1996/march/critter_watch.htm The horn is actually a huge tooth that grows into a long spiral horn. The horn is hollow for most of its length and quite brittle; in roughly one third of individuals, the tusk is broken. But, as far as it shedding it's horn like some species, the Narwhal does not shed it, it simply becomes broken from Male Narwhals using their horns to duel one another , this is referred to as "Tusking". Their is a fantastic picture of Tusking at the above web site.
As far as the purpose of the Narwhals tusk? Their have been all kinds of theories put forwasrd to explain the function of this champion overbite. It has been suggested, for example, that the tusk is used for poking breathing holes in the ice, but observations have shown that narwhals use their rounded foreheads for this purpose. Others have suggested that the narwhal tusk may be used as a weapon against its predators (polar bears, killer whales, and Greenland sharks), but it is hard to believe the fragile tusk would prove a durable weapon. Still others have suggested that the tusk is used to heard small schooling prey (Arctic cod or squids) or prod benthic creatures (crustaceans) from the bottom muck. This is feasible, but the largely sympatric and closely-related beluga manages similar prey just fine without such dental equipment.
The most likely function of the narwhal tusk, however, is as an aid to establishing dominance among rival males. Male narwhals have been documented jousting with crossed tusks, both above and below water. The sound of these conflicts is like two wooden walking sticks being repeatedly banged together. Young males frequently playfight, but rarely spear each other; older males are often seriously scarred after more earnest battles over females - but they, too, rarely spear one another. More than two animals may be involved in such fights, and sometimes others (of either sex) may 'observe' scuffles; it is possible that subadult male narwhals may learn about jousting by watching older males, or that females watch as the males show off in an attempt to win favour.
One of the most interesting theories has been advanced by Canadian scientist Peter Beamish. Narwhals are highly vocal, producing clicks, squeals, growls and whistles; the clicks are narrow-band, pulsed sounds with a frequency of 15-24 kHz. Beamish noticed that the tusks throbbed in a disturbing way when the males were producing their highest frequencies, and he suggests that they may be wave guides which channel the sounds and focus them into tight, directional beams. The sound frequencies recorded for narwhals could be sonar pulses, but they seem to show no variation with approach to obstacles. In the case of males, however, the tusk may conduct sound energy sufficiently close to a rival male's sensitive ears to cause considerable discomfort. A solid tusk would conduct sound energy more efficiently than a hollow one but, as noted above, most mature males have badly scarred heads consistent with tusk-tip slashes. This opens up the intriguing possibility of competing male narwhals fighting acoustic duels, lashing at each other with their sonic lances.
It is also interesting to note that there is also a mystery that surrounds the Narwhal's horn that dates from Medieval times through the 17th century. It seems that during this time period the existence of the unicorn was reinforced by the spectacular spiraling horns that the Vikings brought to Europe. It was believed that the unicorn horn could detect and destroy any poison that an enemy might place in one's food. The Vikings guarded their secret of the source of the horns from the Europeans for over 300 years. The horns were not from the legendary Unicorn, but from the Narwhal.
For more info from books check out the following:
June Wingert, Mad Scientist
Try the links in the MadSci Library for more information on Zoology.