The narwhal is not an aquatic unicorn. It's not magical, or
mythical. It's just a whale with two teeth, one of which happens
to be really long on males. But it's not just its snaggletooth
which can be up to nine feet long that makes this Arctic
sea creature unbelievable. The narwhal sees with sound and
it's exceptionally good at it too, according to a
study published Wednesday in the journal PLOS One.
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In
a photo provided by the National Oceanic and Atmospheric Administration,
a pod of narwhals surfaces in the waters off northern Canada
in August, 2005. Researchers tracked narwhals and found that
they have exceptional echolocation abilities, reconstructing
their underwater world with more resolution that most other
animals on the planet. (Kristin Laidre / NOAA via The New
York Times)
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Like any whale, the narwhal needs to surface to breathe
on average, every four to six minutes. But unlike most whales, narwhals
spend all of their lives in extreme Arctic conditions, primarily
in waters off Eastern Canada and Greenland, where there's more darkness
than light, and more ice than open sea. Somehow, this blubbery bundle
finds its way to cracks in the ice to breathe. Somehow, it can also
hunt for squid and dive down more than a mile into pitch black water
to capture fish and other prey.
"You don't see open water for miles and miles and suddenly
there's a small crack, and you'll see narwhals in it," said
Kristin Laidre, an ecologist at the University of Washington who
led the study. "I've always wondered how do these animals navigate
under that, and how do they find these small openings to breathe?"
Wondering how climate change and the prospect of an ice-free
Arctic might affect narwhal behavior in the future, scientists tracked
these whales over the ice in helicopters. Knowing that whales use
echolocation sending out clicks of sound that bounce off
objects in the environment around them they placed microphones
underwater and listened.
They found that with clicks of sound, like a flashlight switching
on and off, the narwhals scanned their underwater world to receive
narrow snapshots and reconstructed them into a larger acoustic picture
one with more resolution than any other animal on the planet,
with the possible exception of beluga whales.
The clicks, produced in organs known as phonic lips at rates
of up to 1,000 clicks per second, are inaudible to the human ear,
but detectable through special, underwater microphones. They exit
through the narwhal's head, which works like a glass lens, bundling
the sound together and sending it out in a narrow beam that travels
through the water, hitting anything in its path, said Jens Koblitz,
a bioacoustician with the BioAcoustics Network in Germany who worked
on the study. When echoes bounce back, the animal perceives them
with fatty pads in its lower jaw.
Koblitz thinks the narwhal can narrow its beam like an adjustable
flashlight on open ice at the sea surface or prey deep in the ocean,
and then widen it as it gets closer to track its prey, a skill that
has been observed in other echolocating animals like bats.
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In
a photo provided by the National Oceanic and Atmospheric Administration,
a pod of narwhals surfaces in the waters off northern Canada
in August, 2005. (Kristin Laidre / NOAA via The New York Times)
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Other scientists who study whales have praised the work for
managing tough conditions to reveal the importance of the narwhal's
navigation system.
"It is not like a singing humpback whale that spreads the
sound widely and can be heard over long distances," Mads Peter
Heide-Jorgensen, an ecologist at the Greenland Institute of Natural
Resources who was not involved in the study, wrote in an email.
"Narwhals are living a secretive life in the Arctic, but this
study has unveiled one of the secrets from the deep waters in the
Arctic."
Indeed, the narwhal has long evoked mystery since the Vikings
brought their tusks back to Europe with stories of unicorns. But
there's one thing you should know about the tusks, Laidre said:
Males and tuskless females appear to be equally good echolocators.
The tusk is likely just for sexual display, like a peacock's feathers
or a lion's mane. So it's highly unlikely to be used as an antenna
for sending and receiving.
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