There is always an ongoing debate about dolphin intelligence. While most scientists agree about the problem-solving capabilities of dolphins and their advanced communication skill, they still argue about how smart are dolphins.
It is a fact that they can use tools to solve problems, very much like apes. They are also excellent communicating and learning new ways to interact as many investigations are about human-dolphin and dolphin-dolphin communication.
Dolphins can do intelligence tests, and they perform brilliantly on them, so they are problem solvers.
Even more, there is evidence that in some species they can transmit knowledge to new generations, very much like we do.
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