A chimp in West Africa makes a tool to prepare food
Primate experts have found more evidence that chimpanzees, like humans, show cultural diversity.
Habits such as grooming, and the use of stone and wooden tools, vary among nine populations in the wild.
Some chimps inspect each other for parasites, flick the bugs on to leaves, then inspect or kill them. However their neighbours show quite different behaviour, simply squashing the parasites on their forearms.
The research is the second stage of the Chimpanzee Cultures Project, an international study of chimps in Africa.
The project is being co-ordinated at the University of St Andrews, Scotland.
"Co-operation with the best field researchers on chimpanzees, from Europe, Japan and America, is revealing a rich diversity of cultural variation in our nearest living relatives," said William McGrew of Miami University, Ohio, US, who is spending the summer with the Scottish team.
"Knowing that the chimpanzee is an endangered species is an even greater spur to pressing on with our studies," he added.
Chimp technology
Professor McGrew said the team was starting to see new patterns of chimpanzee behaviour emerging.
This ranged from day-to-day activities like gathering food to social organisation, relationships, and the use of simple technology.
Experts have recorded over 40 different types of stone tool use in chimps. In West Africa, apes at several locations use wood or stone tools to crack nuts to feed on the kernels. In East Africa, although nuts are available, chimps don't eat them.
"We continue to be surprised at the extent of chimpanzee elementary technology," Professor McGrew told BBC News Online.
He said the differences from one population to another "cannot be accounted for either by genetic make-up or environmental influences".
"These sorts of differences seem to be the sorts of things that if they occurred in human beings we would call them traditions," he said.
There is evidence that other apes, such as gorillas and orang-utans, show cultural differences, as well as creatures such as whales and dolphins.
Chimp culture could help us understand the evolutionary origins of human culture, Professor McGrew said.