Does it contain a missing link between apes and men? The Guardian reports on the Congo:
The most detailed and recent data comes from Cleve Hicks, at the University of Amsterdam, who has spent 18 months in the field watching the Bili apes - named after a local town - since 2004. His team's most striking find came after one of his trackers heard chimps calling for several days from the same spot.
When he investigated he came across a chimp feasting on the carcass of a leopard. Mr Hicks cannot be sure the animal was killed by the chimp, but the find lends credence to the apes' lion-eating reputation.
"What we have found is this completely new chimpanzee culture," said Mr Hicks. Previously, researchers had only managed to snatch glimpses of the animals or take photos of them using camera traps. But Mr Hicks used local knowledge to get closer to them and photograph them.
"We were told of this sort of fabled land out west by one of our trackers who goes out there to fish," said Mr Hicks whose project is supported by the Wasmoeth Wildlife Foundation. "I call it the magic forest. It is a very special place."