Humans are often defined as the only animal capable of language, yet researchers have recorded a very complex range of animal vocalisations. Some say that these simply reflect the animal’s emotions, such as fear or aggression. Other scholars maintain that animal vocalisations may act as symbols and refer to external things.

In any case, animals tend to develop local dialects and pass them on from generation to generation. In this audio piece, scientists and field assistants in a Nigerian research camp impersonate calls of monkeys and apes.