The Whale Behind the Tusk 
Myths and superstitions concerning the narwhal tooth 
have been a factor in the whale's exploitation 
by Randall R. Reeves and Edward Mitchell 
During the Middle Ages, European 
apothecaries frequently sold “unicorn 
horn,” with the promise that it would 
cure epilepsy, strengthen the heart, in- 
duce perspiration, and buffer poison. 
The substance being offered was, in 
fact, derived from the ivory tooth of the 
narwhal, a small arctic whale. This spe- 
cies ( Monodon monoceros) has only two 
fully developed teeth, both rooted in 
the upper jaw. In males the left tooth 
develops into a straight tusk protruding 
as much as seven or eight feet forward 
from the upper lip, its surface grooved 
in a left-handed spiral. Modern medi- 
cine has long since undermined the 
importance of “unicorn horn” as a 
pharmaceutical panacea, but the nar- 
whal’s remarkable tusk continues to 
stir the human imagination. 
Most scientific explanations for the 
origin and function of the narwhal’s 
tusk have not been tested by direct ob- 
servation because the animal’s high 
Arctic habitat makes study difficult 
and expensive. Casual observations by 
whalers and early naturalists gave rise 
to various speculations. Some argued 
that the tusk is used to poke breathing 
holes in ice; others that it is used to 
spear fish or at least to stir up bottom- 
dwelling prey. More recently, two den- 
tal anatomists speculated that the tusk 
operates as a cooling mechanism, al- 
lowing the well-insulated narwhal to 
dump excess body heat during spurts of 
physical activity. And acousticians 
have wondered whether the tusk might 
be useful in focusing or otherwise en- 
hancing the echolocation signals by 
which the narwhal is believed to navi- 
gate and find food. 
Helen Silverman, while a graduate 
student at McGill University in Mon- 
treal, spent three recent seasons on 
northern Baffin Island studying the so- 
cial behavior of narwhals. She often 
saw the animals crossing tusks with one 
another, both above and below the 
water, an activity noted also by early 
Scottish whalers. Although little ag- 
gressiveness was evident during these 
episodes of tusk crossing, Silverman in- 
ferred that such behavior might help 
maintain dominance hierarchies and 
enable young narwhals to develop the 
skills necessary for performance of 
adult sexual roles. Unfortunately, her 
observations were limited to the sum- 
mer season, June to October, and the 
narwhals’ peak period of effective mat- 
ing falls between March and May. As a 
result, whether narwhals actually use 
their tusks for more serious combat 
during the breeding season could only 
be inferred. 
In addition to watching live nar- 
whals, Silverman and others have ex- 
amined animals killed by Eskimo 
hunters. A relatively high incidence of 
scarring is found on the heads of adult 
males, and more than half of them have 
broken tusks. One heavily scarred indi- 
vidual had a tusk tip embedded in the 
upper jaw near the base of its own tusk. 
This, together with reports of broken 
tusks into which the tip of another tusk 
has been jammed, is evidence that the 
tusk serves an aggressive function. A 
burst in growth of the tusk at sexual 
maturity has been taken as further 
proof of the importance of this appen- 
dage in agonistic confrontations be- 
tween adult males. 
Even if the evidence for its aggressive 
use begins to explain one function of the 
tusk, several interesting questions are 
left unresolved. For instance, of the 
male narwhal’s two adult teeth, why 
does only the left one normally erupt 
through the gum, giving the animal an 
asymmetry rarely found in the natural 
world? Most other mammals with 
horns, tusks, or antlers have them in 
pairs (the one-horned Asian rhinoceros 
being an exception). Curved, paired 
tusks like those of the walrus, elephant, 
wart hog, and dugong are common in 
nature, but straight tusks, such as the 
lower jaw pair in the hippopotamus, are 
rare. The single, straight tusk of the 
narwhal is unique. 
The narwhal’s use of the tusk as a 
weapon need not rule out the possibility 
of other uses. In many large mammals 
bearing horns, antlers, and other ce- 
phalic appurtenances, these structures 
are important as signaling devices. If a 
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