From The Sunday Times
January 3, 2010
Scientists say dolphins should be treated as
'non-human persons'
Dolphins have long been recognised as among the most intelligent of
animals but many researchers had placed them below chimps
Jonathan Leake
Dolphins have been declared the world’s second most intelligent
creatures after humans, with scientists suggesting they are so bright that they
should be treated as “non-human persons”.
Studies into dolphin behaviour have highlighted how similar their communications
are to those of humans and that they are brighter than chimpanzees. These have
been backed up by anatomical research showing that dolphin brains have many key
features associated with high intelligence.
The researchers argue that their work shows it is morally unacceptable
to keep such intelligent animals in amusement parks or to kill them for food or
by accident when fishing. Some 300,000 whales, dolphins and porpoises die in
this way each year.
“Many dolphin brains are larger than our own and second in mass only to
the human brain when corrected for body size,” said Lori Marino, a zoologist at
Emory University in Atlanta, Georgia, who has used magnetic resonance imaging
scans to map the brains of dolphin species and compare them with those of primates.
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“The neuroanatomy suggests psychological continuity between humans and
dolphins and has profound implications for the ethics of human-dolphin
interactions,” she added.
Dolphins have long been recognised as among the most intelligent of
animals but many researchers had placed them below chimps, which some studies
have found can reach the intelligence levels of three-year-old children.
Recently, however, a series of behavioural studies has suggested that dolphins,
especially species such as the bottlenose, could be the brighter of the two.
The studies show how dolphins have distinct personalities, a strong sense of
self and can think about the future.
It has also become clear that they are “cultural” animals, meaning that
new types of behaviour can quickly be picked up by one dolphin from another.
In one study, Diana Reiss, professor of psychology at Hunter College,
City University of New York, showed that bottlenose dolphins could recognise
themselves in a mirror and use it to inspect various parts of their bodies, an
ability that had been thought limited to humans and great apes.
In another, she found that captive animals also had the ability to
learn a rudimentary symbol-based language.
Other research has shown dolphins can solve difficult problems, while
those living in the wild co-operate in ways that imply complex social
structures and a high level of emotional sophistication.
In one recent case, a dolphin rescued from the wild was taught to
tail-walk while recuperating for three weeks in a dolphinarium in Australia.
After she was released, scientists were astonished to see the trick
spreading among wild dolphins who had learnt it from the former captive.
There are many similar examples, such as the way dolphins living off
Western Australia learnt to hold sponges over their snouts to protect
themselves when searching for spiny fish on the ocean floor.
Such observations, along with others showing, for example, how dolphins
could co-operate with military precision to round up shoals of fish to eat,
have prompted questions about the brain structures that must underlie them.
Size is only one factor. Researchers have found that brain size varies
hugely from around 7oz for smaller cetacean species such as the Ganges River
dolphin to more than 19lb for sperm whales, whose brains are the largest on the
planet. Human brains, by contrast, range from 2lb-4lb, while a chimp’s brain is
about 12oz.
When it comes to intelligence, however, brain size is less important
than its size relative to the body.
What Marino and her colleagues found was that the cerebral cortex and
neocortex of bottlenose dolphins were so large that “the anatomical ratios that
assess cognitive capacity place it second only to the human brain”. They also
found that the brain cortex of dolphins such as the bottlenose had the same
convoluted folds that are strongly linked with human intelligence.
Such folds increase the volume of the cortex and the ability of brain
cells to interconnect with each other. “Despite evolving along a different
neuroanatomical trajectory to humans, cetacean brains have several features
that are correlated with complex intelligence,” Marino said.
Marino and Reiss will present their findings at a conference in San
Diego, California, next month, concluding that the new evidence about dolphin
intelligence makes it morally repugnant to mistreat them.
Thomas White, professor of ethics at Loyola Marymount University, Los
Angeles, who has written a series of academic studies suggesting dolphins
should have rights, will speak at the same conference.
“The scientific research . . . suggests that dolphins are ‘non-human
persons’ who qualify for moral standing as individuals,” he said.
Additional reporting: Helen Brooks
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