Читать книгу National Geographic Kids Chapters: My Best Friend is a Dolphin! - Moira Donohue Rose - Страница 7
ОглавлениеTim trains the dolphins to retrieve anything they find. Credit 5
The dolphins already knew how to retrieve (sounds like ree-TREEV) toys. Tim would toss out a ball or hoop. Then he would bend his arm at the elbow, his fingers pointing up. With his palm facing the dolphin, he would push it down, toward the animal. It was the signal to retrieve. The dolphins would bring back whatever toys they found.
The dolphins were so good at retrieving, Tim decided to put this training to practical use. Visitors often dropped things into the dolphin tank by accident. Oops, those were my favorite sunglasses! Dolphins love to make toys out of anything new. But cameras and hats don’t belong in their tank. Tim decided to teach the dolphins to fetch anything that didn’t belong there.
Soon, when Tim gave the retrieve command, a dolphin would sometimes find a toy. But if a dolphin brought back a lost item, she got an extra big fish. Before long, the dolphins figured out that they would get big treats if they found lost items.
Kelly seemed to find items more quickly than the other dolphins. Tim would give the signal, and she would dive straight down. Moments later, she would pop up again. She had something in her mouth every time. Sometimes it was just a small piece of trash. Other times it was a valuable lost item. Tim thought she was very smart. He would soon find out just how smart she really was.
Did You Know?
Different types of wild dolphins eat different types of fish. Some types like salmon, and some chow down on squid. But even though dolphins have teeth, they don’t chew their food! They just swallow it whole.
Some scientists think dolphins are the second smartest animals on Earth. And they have a superpower, too. Dolphins use echolocation (sounds like ek-oh-loh-KAY-shun) to find things. That means they send out a stream of sounds underwater. Click, click, click! The sound bounces back to them. The sound waves form a picture in their minds. From that mental picture, dolphins can tell the size and shape of something. The echo also tells them how close something is. This super talent tells them if danger is nearby. It also helps them find food—or lost items!
The tank where Kelly and the other dolphins swam had windows on the lower level. People could watch the dolphins underwater. The dolphins would flip, twist, and kick. Sometimes they would come up to the windows. They would look at the visitors. One day, Tim was walking by a window. Kelly was floating in front of the window. Tim hadn’t given the retrieve command, but Kelly had a piece of trash in her mouth. As soon as Tim noticed, she turned and splashed up to the surface. Kelly gave him the trash. Tim gave her a fishy treat. He was impressed!
Kelly started waiting at the window for Tim more and more often. Each time, she had a piece of trash or a lost item. Tim wondered, Why does she find so much more trash than the other dolphins? Then he got his answer. One day, the pool was being cleaned. The dolphins were safe in another pool. Tim went into the dry pool. In a far corner was a pile of rocks. Tim looked around them. That’s when he discovered Kelly’s secret. Kelly picked up trash whenever she found it.
Experts used to think that only people and some apes could recognize themselves in mirrors. But Diana Reiss and another scientist did a study with bottlenose dolphins. They found out that dolphins recognize themselves in mirrors, too. And they do more than just look. They study how they look. The scientists put marks on the dolphins. The dolphins swam straight to the mirror. They turned to see the mark better. But unlike chimps, the dolphins didn’t look at marks on each other.
Then Kelly hid it. She had her own private trash stash! Whenever she wanted a treat, Kelly pulled something out. She waited at the window until she caught Tim’s eye. As soon as he took the bait, she swam to the dock where the fish were kept. Tim laughed. She’s being lazy! he thought. But she was also being a smarty-pants. She had figured this out all by herself. And she had outsmarted Tim!
Today, scientists are trying to test dolphins’ intelligence (sounds like in-TELL-i-jens). They have created an experiment called the ELVIS project. The scientists show shapes on an underwater screen. Each shape represents a type of fish. The dolphin must aim its echolocation at the symbol. When it does, the dolphin gets that kind of treat. A dolphin named Luna was the first to learn how to find the right symbol to ask for her favorite.
Experiments like this tell us that dolphins are smart and fast learners. Tim knew that, too. And after Kelly’s tricks, he wanted to know just how smart she was. Tim decided to try a different kind of test. He wanted to compare three dolphins. But it’s hard to find ways to test dolphin smarts. So Tim met with another dolphin expert. Together, they designed a test.
First, they made a special plastic screen. The screen was clear, so the dolphins could see through it. Using a target pole, they taught three dolphins to swim to the screen. Then a trainer dove on the other side of the screen. He gave hand signals for behaviors the animals knew. The trainer would signal for a spin or a wave. Once the animals showed they knew the behaviors, it was time to darken the screen. That made it harder for them to see the signal. Eventually, Tim made the screen completely dark. Now the dolphins couldn’t see the diver with their eyes. They had to use echolocation to “see” his signal. Pretty soon, they understood. Next, Tim used a computer to give him signals in a random order. He told the trainer who was hidden behind the screen what signal to give. The dolphins had to read the diver’s signal and perform the right action. All three passed the test. One dolphin got it correct more than 90 percent of the time. It was Kelly, of course!
