dolphin intelligence

Humans have known for a long time that dolphins are intelligent creatures. But the more we study them, the more intelligent we find they are.

At the Institute for Marine Mammal Studies in Mississippi, dolphins are trained to clean their own pools; if they bring trash to the trainers, they will receive a reward of fish.

One dolphin named Kelly has figured out how to maximize her payoff:

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 goes down to the rock and 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.

Kelly has learned how to save for the future. And that's not all:

One day, when a gull flew into her pool, she grabbed it, waited for the trainers and then gave it to them. It was a large bird and so the trainers gave her lots of fish. This seemed to give Kelly a new idea. The next time she was fed, instead of eating the last fish, she took it to the bottom of the pool and hid it under the rock where she had been hiding the paper. When no trainers were present, she brought the fish to the surface and used it to lure the gulls, which she would catch to get even more fish.

After mastering this technique, Kelly taught it to other dolphins. The dolphins have learned how to make wise, high-yield investments.

But there's more. In a famous experiment by Karen Pryor, dolphins demonstrated the ability to think creatively:

Two rough-toothed dolphins were rewarded whenever they came up with a new behaviour. It took just a few trials for both dolphins to realise what was required. A similar trial was set up with humans. The humans took about as long to realise what they were being trained to do as did the dolphins. For both the dolphins and the humans, there was a period of frustration (even anger, in the humans) before they "caught on". Once they figured it out, the humans expressed great relief, whereas the dolphins raced around the tank excitedly, displaying more and more novel behaviours.

Wild dolphins have even been observed using tools:

Scientists have observed a dolphin coaxing a reluctant moray eel out of its crevice by killing a scorpion fish and using its spiny body to poke at the eel. Off the western coast of Australia, bottlenose dolphins place sponges over their snouts, which protects them from the spines of stonefish and stingrays as they forage over shallow seabeds.

And now they've evolved opposable thumbs:

[M]arine biologists at the Hawaii Oceanographic Institute reported Monday that dolphins, or family Delphinidae, have evolved opposable thumbs on their pectoral fins.

OK, that last one isn't real; it's from the Onion. For the rest, see this article from The Guardian. And here is Karen Pryor's research paper on dolphin creativity.

Dolphins truly are a fascinating species.