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Mexico
beach towns say NO to cruise ships
Researchers: Dolphins use sponges as
tools
US
media investigates the dolphin captivity industry
Environmental
activism according to Sea World,
a PBS Frontline Interview with Susan Davis
July 6, 2003
OKAYAMA -- A woman has sued a hotel for injuries she sustained during
a swimming pool attraction enabling guests to "come in contact with
dolphins."
The woman, 37, from Okayama, whose name is being withheld, and her relatives
stayed at the Taiji Seaside Ichinoyu Hotel at the southern tip of the
Kii Peninsula in Wakayama Prefecture in July last year.
While she was swimming in the hotel's pool, one of three dolphins smashed
into her back, breaking several bones in her ribcage and back, the suit
says. She sought medical treatment from doctors for some 6 months after
the accident.
The woman now demands in the suit that the hotel pay some 2.8 million
yen in damages as she insists that she still suffers from numbness in
her lower back.
Mainichi Shimbun, Japan, June 7, 2003
June 6, 2005
Courtesy Proceedings of the National Academy of Sciences and World Science
staff
Scientists are studying an extended family of dolphins in Western Australia
who use tools, and have concluded that the behavior is a family tradition.
The bottlenose dolphins break marine sponges off the seafloor and wear
them over their snouts to probe into the seafloor for fish, the first
known case of tool use among marine mammals. It's well known that chimpanzees
and orangutans use tools. Scientists have recently come to define thisactivity
as animal "culture" because it is transmitted through generations,
and takes different forms in different animal groups.
Now, researchers say the same should be said of dolphins.However, theirs
might not be an equal-opportunity culture: "sponging" seems
to be almost exclusively a female job.
It in fact appears to be a cultural behavior passed from mother to daughter,
said the researchers, led by Michael Krützen of the Anthropological
Institute and Museum at the University of Zurich, Switzerland. They described
the findings in a paper in the early online edition of the Proceedings
of the National Academy of Sciences, a research journal, this week. The
spongers are a group of wild dolphins in Shark Bay, Australia. Krützen
and colleagues proposed that because almost all are related, they likely
descend from one "sponging Eve" who invented the technique.
It is not clear why so few males do it, as they spend as much time with
their mothers as females do, the researchers added.
The scientists analyzed DNA from 13 spongers, only one of which was male,
and 172 non-spongers. Bottlenose dolphins in Shark Bay have previously
been spotted used nearly a dozen different tactics for food foraging,
though none of the other methods involve tools. Sponging has been seen
in 15 of 141 known mothers in the Shark Bay bottlenose dolphin population,
the researchers wrote.
They rejected two alternative explanations for the sponging that wouldn't
involve a tradition or culture: a genetic, and a so-called ecological
explanation. The genetic explanation proposes that sponging is due to
a "sponging gene" or genes, rather than because of tradition
or learning.
This is unlikely, the researchers said, because because genes tend to
be passed down in specific patterns, depending among other things on which
chromosomes they are in. None of the known patterns matched the documented
one for sponging, in which mostly females, but at least one male, engaged
in the activity. The ecological explanation would state that particular
features of the dolphins' environment are, by themselves, enough to stimulate
sponging. This is also improbable because both spongers and non-spongers
shared the same feeding and foraging areas, the researchers reported.
The rejection of both the genetic and ecological explanations leaves only
one, cultural transmission, they argued.
"A behavioral trait is considered to vary culturally if it is acquired
through social learning" and is "transmitted repeatedly within
or between generations," the researchers wrote. "Bottlenose
dolphins are highly imitative and capable of social learning, both in
the wild and in captivity."
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