But several animal species are capable of one or more of these abilities, e.g. chimpanzees and dolphins. The dolphin is considered to be the most linguistically promising because of its large brain size and because of the range of sounds it can make. MOST studies have been done on the Atlantic bottle-nosed dolphin Tursiops truncatus . Tursiops' brains are large and well developed. The brain to body ratio of the dolphin is the largest of any non-human mammal and is twice as great as the chimpanzee.
Dolphins have a complex echolocation system that they use in hunting.
However, the large brain is not apparently necessary to support this because some bats have an equally sophisticated echo-location system but one of the smallest mammalian brains. The large dolphin brain more likely explains their complex social system. Complexity of social relations in mammals is correlated with brain size. It is proposed that human language is an evolutionary offshoot of that process. Dolphin society may rival primate society in complexity.