Intelligence is not limited to humans. Many animals also show signs of intelligence: Animals also need to solve problems, and remembering how a problem is solved is useful to them. Many animals use tools to solve problems. These animals include the Great Apes, dogs, dolphins, elephants, rats and mice, and some birds. All these animals are vertebrates, but tool use isn't limited to these: Even cephalopods and arthropods show signs of intelligence. To be able to compare the behaviours of different species, scientists need to adapt the notion of intelligence. 