December 13, 2005

Narwhal’s tusk is a giant sensor: study

WASHINGTON (Reuters) - The narwhal's mysterious spiral tusk
works as a giant sensor to help it test water qualities and to
smooch other narwhals, a U.S. researcher said on Tuesday.

The whale's eight-foot (2.4-meter) long tusk has long
mystified naturalists and hunters, and the explanation may be
equally intriguing, Harvard School of Dental Medicine
researcher Dr. Martin Nweeia said.

The tusk, it seems, has hydrodynamic-sensing capabilities,
Nweeia said in a statement released ahead of his presentation
to the Conference on the Biology of Marine Mammals in San

The mammals are among the rarest of whales, usually 13 to
15 feet long, found mostly in the Arctic Ocean waters of Canada
but as far east as Russia.

Nweeia's team found that the narwhal tusk is like a
membrane with an extremely sensitive surface. It has 10 million
nerve connections to the outer surface that would be capable of
detecting changes in water temperature, pressure, and salinity.

"There is no comparison in nature and certainly none more
unique in tooth form, expression, and functional adaptation,"
Harvard said in a statement.

Anyone with sensitive teeth who has bitten into an ice
cream would wince.

"Why would a tusk break the rules of normal development by
expressing millions of sensory pathways that connect its
nervous system to the frigid arctic environment?" Nweeia asked.
"Such a finding is startling and indeed surprised all of us who
discovered it."

Nweeia's team also noted that narwhal males will rub tusks
and said it was likely this provided the big animals with a
"unique sensation."

"Now that we know the sensory capabilities of the tusk, we
can design new experiments to describe some of the unique and
unexplained behaviors of this elusive and extraordinary whale,"
said Nweeia.