Deep in the Congolese jungle is a band of apes that, according to local legend, kill lions, catch fish and even howl at the moon. Local hunters speak of massive creatures that seem to be some sort of hybrid between a chimp and a gorilla.
Their location at the center of one of the bloodiest conflicts on the planet, the civil war in the Democratic Republic of the Congo, has meant that the mystery apes have been little studied by Western scientists. Reaching the region means negotiating the shifting fortunes of warring rebel factions and the heart of the animals' range is deep in impenetrable forest.
But despite the difficulties, a handful of scientists have succeeded in studying the animals. Early speculation that the apes may be some yeti-like new species or a chimp/gorilla hybrid proved unfounded, but the truth has turned out to be in many ways even more fascinating. They are actually a population of super-sized chimps with a unique culture -- and it seems, a taste for big cat flesh.
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. 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," Hicks said. Previously, researchers had only managed to snatch glimpses of the animals or take photos of them using camera traps.
"We were told of this sort of fabled land out west by one of our trackers who goes out there to fish," said Hicks, whose project is supported by the Wasmoeth Wildlife Foundation.
"I call it the magic forest. It is a very special place," he said.
Getting there means a gruelling 40km trek through the jungle, from the nearest road, not to mention navigating croc-infested rivers. But when he arrived he found apes without their normal fear of humans. Chimps near the road flee immediately at the sight of people because they know the consequences of a hunter's rifle, but these animals were happy to approach him.
"The further away from the road the more fearless the chimps got," he said.
Unlike their cousins in other parts of Africa, Hicks said, the chimps regularly bed down for the night in nests on the ground. Around a fifth of the nests he found were there rather than in the trees.
"How can they get away with sleeping on the ground when there are lions, leopards, golden cats around as well as other dangerous animals like elephants and buffalo?" Hicks said.
"I don't like to paint them as being more aggressive, but maybe they prey on some of these predators and the predators kind of leave them alone," he said.
"The ground nests were very big and there was obviously something very unusual going on there," said Colin Groves, a specialist on primate morphology at the Australian National University in Canberra.