Secrets of whales' long-distance songs unveiled ,
China daily 3-23-05
Date: Wed, 23 Mar 2005 18:43:35 -0800
Secrets of whales' long-distance songs unveiled
www.chinaview.cn 2005-03-23 10:48:09
BEIJING, March. 23 -- Long ago scientists
discovered whales could
sing.
They can utter different sounds to express anger,
surprise and sadness
with
the changes of environments and their physical
conditions.
Long ago scientists discovered whales could sing. They
can utter
different
sounds to express anger, surprise and sadness with the
changes of
environments and their physical conditions.
It was also discovered that whales in the North
Atlantic Ocean seem
to
be moving together and coherently, even when they were
far away from
one
another.
Why do whales move in such a way? What is
impelling them forward?
How do
they communicate with each other, seemingly over
thousands of miles of
ocean?
For nearly nine years, Christopher Clark, a
researcher from Cornell
University of the United States, has been trying to
answer these
questions
by listening to whale songs and calls in the North
Atlantic using the
navy's
antisubmarine listening system. The underwater
microphones of SOSUS
(Sound
Surveillance System) can track singing blue whales,
fin whales,
humpback
whales and minke whales.
A world linked by songs
There is a time delay in the water, and the
response time for
whales'
communications is different from the time of human
beings. Sounds are
transmitted in the water at a speed of 1,450 meters
per second. This is
four
times faster than the transmission speed in the air.
As a result, when
whales communicate via songs, the responses come much
quicker.
Because humans still know so litte about whale
communications,
Clark and
his team decided to observe whale patterns of
association and
coordination.
Although the whales are spaced far apart, the
SOSUS system provided
a
wealth of new data. Through weeklong soundings, Clark
obtained
thousands of
acoustical tracks of singing whales from different
species throughout
the
year.
"We now have evidence that they are communicating
with each other
over
thousands of miles of ocean. Singing is part of their
social system and
community," Clark said.
Excellent singers by birth
Whale songs have a much bigger wavelength than
human songs. The
songs
are very pleasant to the ears of whales born as bel
canto singers.
Scientists have also discovered that whales sing
new songs each
year.
New syllables appear constantly to replace old ones
and the new
syllables
soon spread worldwide. By using the tracking system,
scientists have
found
that a whale in Hawaii sings a similar song to a whale
in Bermuda. They
also
found that when a horde of whales return to their
original territory
after
long-distance trips, they first sing old songs of the
previous year and
then
new songs.
Information transfer via songs
Why do whales sing? Scientists think that they
sing to locate their
positions and to transfer information.
Whales will aim directly at a seamount that is 300
miles away, then
once
they reach it, change course and head to a new
feature. It is as if
they are
slaloming from one geographic feature to the next. It
means they must
have
acoustic memories much like our visual memories.
Whales communicate with each other via songs. To
avoid sending
information to their enemies, they use a unique
low-frequency, which
can
only be heard by allies.
It is still unclear why whales make long-distance
movements. What
is
influencing their movement and distribution? What are
the ocean
features
whales are honing in on?
Threats on whales' habitat
Just as researchers gain new ways of understanding
the linkages
between
whales and oceanographic features, what they hear is
the rising tide of
noise from an increasingly urbanizing marine
environment � the
collective
noises from shipping traffic, oil and gas exploration
and production,
and
recreational traffic. And every decade the amount of
noise is doubling.
"Many whales have very traditional feeding grounds
and their
migratory
routes occur along shallow coastlines, which are now
some of the
noisiest,
most heavily impacted habitats," Clark explains. But
often it is along
these
routes that the male songs are sent long distance to
prospective
females,
who might not receive the message through the "ocean
smog."
"If females can no longer hear the singing males,
they lose
breeding
opportunities and choices. The ocean area over which a
whale can
communicate
and listen today has shriveled down to a small
fraction of what it was
less
than a century ago," said Clark.
(Source: Shenzhen Daily)
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