How smart are dolphins? Anuschka de Rohan reviews the evidence, including an underwater-tv encounter between a dolphin and David Attenborough.
At the Institute for Marine Mammal Studies in Mississippi, Kelly the dolphin has quite a reputation. All the institute's dolphins are trained to hold onto any litter that falls into their pools until they see a trainer, when they can trade the litter for fish. Kelly took this task one step further. When people drop paper into the water she hides it under a rock at the bottom of the pool.
The next time a trainer passes, she tears off a piece of paper to give to the trainer. After a fish-reward, she goes back down, tears off another piece of paper, gets another fish, and so on. This behaviour is particularly interesting because it suggests that Kelly has a sense of the future and delays gratification. She has, in effect, trained the humans.
Problem-soving with tools
Despite their lack of hands, dolphins can also use tools to solve problems. Scientists have observed a dolphin trying to get a reluctant moray eel to come out of its crevice by poking it with the spiny body of a dead scorpionfish. In Australia, bottlenose dolphins place sponges over their snouts as protection from the spines of stonefish and stingrays as they forage over shallow seabeds.
Many species of dolphin live in complex societies. To keep track of the many different relationships within a large social group, it helps to have an efficient communication system. Dolphins use a variety of clicks and whistles to keep in touch. There is currently no evidence that dolphins have a language of their own. But we've barely begun to record all their sounds and body signals let alone try to decipher them, and so there are certain to be a few surprises in store.
Communicating with sign language
At Kewalo Basin Marine Laboratory in Hawaii, Lou Herman and his team have developed a sign language to communicate with the dolphins, and the results are remarkable. Not only do the dolphins understand the meaning of individual words, they also understand the significance of word order in a sentence. For example, they generally responded correctly straight away to "touch the frisbee with your tail and then jump over it." This has the characteristics of true under- standing, not rigid training.
In the BBC programme Wildlife on One: Dolphins - Deep Thinkers?, one of Lou Herman's dolphins, Akeakamai, watches David Attenborough on an underwater tv screen. No one could predict how she would react, but as soon as David appeared on the screen, she responded correctly to his sign language, and even had a go at imitating him.
Despite inhabiting a very different world to ourselves, dolphins perform brilliantly in our 'intelligence tests'. There is still much to learn about these flexible problem-solvers, but from the evidence so far, it seems that dolphins do indeed deserve their reputation for being highly intelligent.
Learning from their peers
Up to now, many scientists have concentrated on the cultural transmission of behaviour from mother to offspring, but new research by Stan Kuczaj and his team have revealed some surprising results. They have noticed that, during play, calves are more likely to copy and learn from dolphins closer to their own age group.
Whether they're swimming through bubble rings or balancing pieces of kelp on their tails, young dolphins increase the complexity of their play behaviour most of all when they're in the company of their peers.
Most mammals seem to enjoy play - but dolphins seem to like making their games as challenging as possible. A killer whale calf learned the trick of luring gulls to the surface of the water with fish. When the gulls landed on the water, the killer whale would then attempt to capture them in her mouth, without killing them.
Once she mastered this skill, she made the task more challenging for herself: instead of waiting for the gulls to land on the water, she tried to capture the gulls on their descent when they were more than a metre above the water surface.
She failed many times but kept going until she got good at it. More often than not, it was the naive juvenile gulls that were caught and subsequently tossed around. The next difficulty level entailed trying to catch the more clued-up, older gulls. As with human children, the activity itself, not just the outcome, has to be fun.
On a beautiful day in 1997, researchers working at Pereirinha beach, off the southern coast of Brazil, observed a little dog going into the sea and swimming towards the dolphins. To their surprise, the dolphins approached the dog and then started throwing it into the air. The dog seemed to enjoy the 'game' and continued playing with the dolphins for more than an hour. From then on, different dogs were seen trying to interact with the dolphins.
From an original article in the July 2003 issue of BBC Wildlife Magazine - Ocean masters
Tags: Dolphins Animals Biology Science Education