The BBC's Sue Nelson: Chimps in Africa display a rich cultural tradition

The discovery shows that our closest animal cousins are even more like us than we thought.

A major study, involving seven chimpanzee sites across equatorial Africa and an international team of researchers, pooled a total of 151 years of chimpanzee observations.

It revealed remarkable differences in the behaviour of the chimpanzees in different groups.

Personal grooming

For example, each had their own distinct ways of grooming, gathering ants, probing bee hives for honey, cracking nuts and making threats. These are passed down from one generation to the next.

Chimps: A rich spectrum of behaviour

A biological definition of culture is the ability to pass on behaviour through social learning, as well as through the genes, so in that sense chimps now join humans as the only cultured beings on Earth.

"Chimp communities differ from each other not in just one behaviour, but in a whole suite of patterns," says the team leader, Professor Andrew Whiten at St Andrew's University in Scotland

"This seems much more like what we see in human cultures, where different societies vary in many ways, like their technologies, cuisines and manners," he says.

Culture clash

The team looked at 65 different behaviours, but ruled out differences in 26 of them as being the result of environmental or ecological factors. For example, chimps living in areas where many lions and leopards roamed slept in tree nests, not ground ones.

But this left 39 differing behaviours which were truly cultural.

In West Africa, a chimp will remove a tick from the fur of a friend, place the bug on its forearm, and crush it with a jab of the forefinger. But at Gombe, Tanzania, the parasite will be placed on a leaf before being squashed.

And chimps at one site in Uganda go as far as picking a leaf, placing the bug on it for inspection, and then either discarding or eating it.

Credibly cultural

Frans de Waal, at the Yerkes Regional Primate Research Centre, Atlanta, US believes the chimpanzees deserve their place as cultured creatures.

"The evidence is now overwhelming that chimpanzees have a remarkable ability to invent new customs and technologies, and that they pass these on socially rather than genetically," he says, writing in the journal Nature, in which the study is published.

Professor Whiten believes the findings emphasise the "continuity of human nature and the rest of the natural world".

They also made more poignant the plight of chimpanzees being decimated by loss of habitat and the African appetite for bush meat. Professor Whiten said: "We are not just losing the chimpanzee. We are losing a diversity of chimpanzee culture."