WildLife Group
of the SAVA
The Violent Purpose of The
Narwhal's Tusk
Article taken from Science Alert: https://www.sciencealert.com/never-before-
seen-behaviour-reveals-the-violent-purpose-of-the-narwhal-s-tusk
15 MAY 2017
Drone footage has captured something no one's ever
seen before - wild narwhals using their bizarre tusks to
hunt Arctic cod by hitting and stunning them, making
them easier to consume.
when they measured the whales' echolocation skills,
they found that they have the most directional sonar
ever detected.
The behaviour addresses a biological mystery that's
spanned decades - why these rare and elusive whales
have evolved an extra-long left canine tooth that
bursts through the upper lip and protrudes from the
head like the horn of a unicorn. Like dolphins and other whales, they're able to
navigate dark, murky waters by producing clicking
sounds at a rate of up to 1,000 clicks per second, and
using the echoes to reconstruct their surroundings
based on how the sound waves bounce off nearby
prey or rock formations.
The footage was captured by two drones in Tremblay
Sound, Nunavat, in northeastern Canada, which were
operated by Adam Ravetch from the World Wildlife
Fund (WWF) Canada and researchers from Fisheries
and Oceans Canada. Previous research had found that the narwhal tooth
had foregone the protection of hard, external enamel
to make it sensitive to even the tiniest of stimuli - and
this appears to have given them the edge over all
other echolocating species.
"This is an entirely new observation of how the tusk is
used," Brandon Laforest, a senior specialist of Arctic
species and ecosystems with WWF-Canada, told
National Geographic. Scientists suspect that the tooth plays a role in
echolocation by allowing seawater to enter it through
pores in its tip. Bubbles then travel through the shaft
and excite nerve endings at the base of the tooth
near the head, sending signals to the brain about
the narwhal's surroundings. This sensitivity suggests
that the narwhal tusk isn't something to be used
haphazardly - you'll notice in the footage above that
those hunting taps are extremely gentle. It also
reveals the cost of narwhal territorial battles (as seen
in the image at the top of the page), which involve
bashing their most sensitive appendages against each
other.
The mystery of these 'horns' - which can grow up to
2.7 metres (9 feet) long - has led scientists to pose
a number of possible functions, including signals of
testicle size, navigation, and territorial battles.
But there's been one obvious gap in the evidence -
these things look a whole lot like weapons, so are they
using them to hunt too? Turns out, they are, as you
can see in the footage.
Now that we've witnessed this behaviour for the
first time, it's become clear that the narwhal tusk is
a multipurpose appendage that really was worth the
cost of evolving the most unusual tooth in nature.
Late last year, researchers discovered that this tusk
helps narwhals 'see' like no other species on Earth -
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We should note that the behaviour in the drone
footage has not been published in a peer-reviewed
journal at this stage, so any interpretations of
what we're seeing will have to be independently
verified. But this is the first time we've ever seen
the mysterious narwhal tusk being used for hunting,
which could be the final piece of the puzzle for this
bizarre oddity of evolution.