Unit11-Part1-Reading

Dolphin intelligence.

We all know that dolphins are very intelligent,

but they are more intelligent than we think.

They are able to learn from experience.

They can pass on their skills to other dolphins too.

This kind of intelligence is very rare in the animal kingdom.

One of those extremely intelligent dolphins is Billy.

Years ago, Billy was trapped in a lake

on the South Australian coast and got sick.

He couldn't return to the sea.

Then some fishermen rescued him and brought him to a marine park.

Billy stayed in a big dolphin tank there.

When he recovered three weeks later,

scientists released him back into the wild

and he swam to his home off the coast.

A few months later, Billy began tail -walking.

To do this, dolphins leap out of the water backwards

and move backwards through the water on their tails.

Tail -walking is unusual for wild dolphins

because special training is necessary for it.

Scientists were amazed when they saw Billy tail -walking in the sea

because he had no training.

They say he probably learned it by watching the other dolphins

in his tank in the marine park.

Those dolphins were able to do some tricks in their shows.

Billy soon began to teach tail -walking to his friends in the sea too.

Now, most of them are walking on their tails for fun.

Also, there's Kelly.

Kelly lives in a research center in the U .S.

Her trainer taught her to keep her tank clean.

When Kelly picks up a piece of litter from the tank,

the trainer rewards her with a fish.

Kelly also created a trick for earning more fish.

When she finds a piece of paper in the tank,

she puts it under a stone at the bottom.

Then she tears off small pieces

and brings the pieces to the trainer, one at a time.

This way, each time she brings a small piece,

she gets one more fish.

Now, she is teaching her calf the same trick.