For the longest time scientists have put the intelligence of dolphins on an even par or even slightly lower than that of chimpanzees. However recent studies have made scientists re-evaluate their assessment of just how intelligent dolphins are.
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.
In the usual standard used by scientists, that being the brain size relative to body size, dolphins are also providing some surprises. Scientists have found that the cerebral cortex and neocortex of the bottlenose dolphin were so large that “the anatomical ratios that asses 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.
All I can say on a personal level is that it’s about time.