Ugandan and French scientists have for months been observing the behaviour of a group of chimpanzees whose uncanny aptitude for self-medication could help their human cousins discover new drugs.
The great apes' ability to treat ailments by adjusting their diet has long been observed by scientists, including world-renowned primatologist Jane Goodall, but a project in Uganda's Kibale forest offers a unique opportunity for pharmaceutical research.
"It's the first time that a chimpanzee observation aimed at discovering new medicine for humans is conducted within a scientific framework," said Sabrina Krief, a French veterinary and professor at the Paris National History Museum.
Uganda is an ideal research ground for the scientists' double mission of better understanding the chimps' behaviour and using them as guides towards new molecules -- and potentially new drugs.
"Uganda happens to be a country where eight of the 16 centres of endemic plants in the whole of Africa converge," said John Kasenene, professor of botanics at the University of Makerere in Kampala.
The university is conducting the project in partnership with the Natural History Museum in Paris, France's National Centre for Scientific Research (CNRS) and the Uganda Wildlife Authority.
Should a new drug be discovered through the project, the memorandum of understanding signed by all the partners includes a revenue-sharing clause.
The Kibale equatorial forest, located some 250 kilometres (130 miles) west of the capital Kampala, offers a high concentration of primates.
"There are very few research stations in the world where chimps have been so well accustomed to being in the presence of human observers," said Krief, who heads the chimp project there.
The key moment in the observation is when one among the group of around 50 chimps she monitors gets sick.
The primate's choice of food -- what he pulls out of his medicine chest -- is packed with information that could lead the scientists to new discoveries.
"We want to compare which plants are used by the traditional healers or traditional practitioners, and the medicines used by chimpanzees. Is there a relation for the kind of treatment they go for?," Kasenene said.
At dawn the team collects the animal's faeces from under that night's nest and carry out a range of analyses.
Krief explained how a chimp named Yogi, suffering from intestinal worms, ingested Aneilema aequinoctiale leaves in the morning and Albizia grandibracteata bark in the evening.
Such plants have been used in traditional medicine in some areas and the Kibale team later confirmed through in vitro testing that they acted against parasites.
Another male chimpanzee who had been feverish and weak was observed eating only Trichilia rubescens leaves for a whole day.
The plants' molecules, later isolated by the scientists in a laboratory, were found to be effective against malaria.
"These findings have allowed us to discover new plant molecules with significant properties against malaria, worms or tumours," Krief said.
Dennis Kamoga, a botanics researcher from Makerere University, is tasked with collecting samples from plants ingested by chimps that will later be analysed in both France and Uganda.
"What is surprising to me is that these chimps have no chemist, no lab... They simply move in and collect plants and eventually find themselves getting cured," the 27-year-old marvelled. "It's a proof that they are very close to us."
Around 100 different kinds of plants have already been sampled in Kibale since the start of 2007.
"It's quite rare to find active molecules but especially new molecules which might put us on the path to developing new pharmaceuticals," which is the ultimate goal of the project, Krief said.
The French scientist said she hoped that, while advancing medicine for humans, the research project in Kibale could also contribute to "a better understanding and protection of the flora and the great apes" in the forest, both of which include critically endangered species.