Talking chimpanzee: apes use screams to send out social signals

Words may not come easily to them but it appears the communication barrier between mankind and our nearest animal relatives may be narrower than we thought. Scientists have found that, when chimpanzees want to make a point, the message is loud and clear.

Chimps are mankind's closest relations in the animal kingdom, sharing 95 per cent of our DNA and many of our characteristics - including the ambition and aggression which leads to arguments and occasional violence. They may have some of our basic communication skills too.

After two years of research, psychologists from the University of St Andrews believe that subtle differences in vocalisations may have been developed to provide important clues for nearby allies. Led by a PhD student, Katie Slocombe, the research team found that chimpanzees scream differently depending on whether they are the aggressor or the victim and these calls are intended to tell nearby allies and relatives about the identity and social role of the group members involved in a fight.

Watching chimps may then use this information to decide whether or not it is necessary to intervene in an ongoing fight. "Chimpanzees who are the victim of an attack produce screams acoustically different from the attacking chimpanzee," said Ms Slocombe, who spent eight months in the Budongo forest, in Uganda, studying wild chimpanzees. "The acoustic differences were consistent across all 14 individuals observed, suggesting chimps produce reliable information about their social role during a fight.

"In their native rainforest habitat this may provide important clues for nearby friends, allies or relatives, particularly as to whether or not they should approach and intervene in an ongoing fight."

Previous research by scientists indicated that chimps have a "vocabulary" of about 30 "words" or sounds that enable them to communicate with other members of their groups. But this research suggests the chatter used by chimps may be much more complicated and detailed than initially thought.

Ms Slocombe said: "The next step is to conduct playback experiments to see what other chimps gain from hearing the screams. Our theory is that chimps unable to see the fight will be able to gain important social information from just listening to the screams, just as we would overhear a conversation and gain information from it."

Language is among the few exclusive behaviours which sets humans apart from the rest of the animal world; there is no comparable evidence of any sort of language among other species. Ms Slocombe added: "We are looking at the evolution of communication. At one time, animal communication was seen as just emotional in that they made certain noises when they were happy and certain noises when they were sad. We think it is more complex than that."