Dolphins are aquatic animals that are closely related to whales and porpoises. They usually live in the ocean, but some live in the river, like the Chinese river dolphin. There are 40 kinds of dolphins in the world, and they have a great difference between their sizes. The smallest dolphin is Maui’s dolphin, and the biggest is Killer whale. Dolphin’s brain have two sides to take turns to rest, they rest one hemisphere of their brains at a time for about 15 to 20 minutes, and they rest for several times a day. Since dolphin’s brains are extremely well developed, they are said to be the smartest animal in the ocean.

         Dolphins are indeed ultra-high-IQ animals. They can perform many difficult and wonderful tricks after trainers train them. For example, playing basketball, high jumping, jumping over hula loops, singing with people, and some of the dolphins can even draw pictures. They are not only intelligent but also very kind to humans. There are lots of events which are about dolphins saving people, like they save people who are drowning, protect people from being hurt by sharks and so on. Since people found out about their intelligence, we train them not only to entertain people at the aquarium, but also rely on their cleverness to complete many complex military mission. Their intelligence and wisdom isn’t just reflected in how they save people, dolphins also have their own language. Every dolphin has their own voice to be their own sign and also use it to contact others. They also know how to search for missing dolphins by releasing signals, they can even understand the meaning of artificial sounds. A few years ago, dolphin research organization Speak Dolphin once recorded dolphins’ sounds and translated them into images by using sonar equipment. They discovered that human beings are just like little cute animals to dolphins.

       Besides saving people and entertaining people, dolphins can also be used to cure some mental illness and developmental retardation. For example, research in 2005 discovered that dolphins can help alleviate the symptoms of depression in some patients. Dolphins are such a great animal that people got a lot of help from them, so we have to stop hunting them and keep them away from the crisis of extinction.