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Whales Can't Hear Love Songs of Potential Mates |
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By Francesca Colombo*
Whales
along Italy's northwest Mediterranean coast are unable to reproduce.
The culprit is severe noise pollution, which drowns out mating calls.
GENOA, Italy - The whales inhabiting the waters
off Italy's Liguria coast are in danger of remaining forever ''single''
because of communication problems caused by too much extraneous
noise.
The so-called Ligure Sea, which comprises the Gulf of Genoa and
the northern Tirreno Sea in the Mediterranean, is known as a ''whale
sanctuary'', but the daily merchant ship traffic causes so much
noise that it has become nearly impossible for the giant water mammals
to communicate with each other.
Found in these waters are fin whales (Balaenoptera physalus), one
of the species of baleen whales, which have sieve-like plates instead
of teeth, used to filter krill, plankton and small fish.
The males emit certain sounds to attract the attention of females,
who indicate whether they are ready for mating, ''especially in
the winter months, and with greatest volume and frequency in February
and March,'' Fabrizio Borsani, a marine acoustic researcher with
the Rome-based marine research institute, ICRAM, told Tierramérica.
The whale ''song'', which sounds like hammer strikes, would be heard
up to 500 kilometers away if there is no interference. But the female
whales in the Ligure Sea don't hear the males' call, ''and there
is a danger that they will be left single,'' said Guido Ognone,
research coordinator at the Genoa Aquarium.
An ICRAM study conducted between 1999 and 2003 found that the Gulf
of Genoa and northern Tirreno Sea are among the world's noisiest
marine areas due to ship traffic, especially merchant ships.
Some 300 tanker ships alone pass through the area each year, carrying
18 million tons of petroleum and its derivatives to northern Europe.
ICRAM recorded 16,000 hours of whale song, using 18 devices with
micro-computer chips placed at depths of 600 to 2,000 meters, and
found that on a daily basis the sounds from ships interrupt 97 percent
of the whales' messages.
According to the researchers, that means that every 24 hours there
are only 43 minutes free of noise, not enough for the whales to
finalize their mating communications.
The fin whale can measure 24 meters long and weigh 60 tons, with
a lifespan of around 90 years. Its strong musculature allows these
undersea giants to swim at a rate of 40 to 50 km per hour.
Hundreds of whales inhabit the Mediterranean Sea, and spend most
of their time alone, covering hundreds of kilometers each day.
The reproductive capacity of the baleen whales is relatively low,
with an average of three offspring in a lifetime. Females are ready
to become mothers at around age 14, and males are sexually active
beginning at 18.
The gestation period ranges from 12 to 16 months, and mothers nurse
their young for one year. The baby whales consume some 200 liters
of milk daily.
Faced with the ''noise explosion'' of the last century, much of
it resulting from more and bigger ships, ''it is possible that the
whales have increased the volume and frequency of their song, but
that remains a hypothesis to be tested,'' said Ognone.
In any case, it is clear that noise pollution is harmful to the
sea's inhabitants, and is why United Nations and European Union
agencies are seeking ways ''to limit human activities in the sea,
but there have been no results nor changes in direction,'' Maria
Teresa D'Agostino, head of the marine campaign for LAV, an Italian
animal rights group, said in a Tierramérica interview.
According to ICRAM, to prevent further harm to whales, it is essential
to regulate ship traffic in the navigational corridors, establish
preferential routes, and build vessels, ports and other infrastructure
that reduces noise pollution.
The World Wildlife Fund reports that a quarter of whale species
are in danger of extinction. The populations where decimated by
hunters in the past centuries, and continue to be threatened by
toxic substances in the seas and oceans.
Furthermore, the International Whaling Commission estimates that
300,000 whales die each year, trapped in fishing nets.
The whales off the Liguria coast face all of these threats.
* Francesca Colombo is a Tierramérica contributor.
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