The tiny community of apes lives in a forest around the village of Bossou, in the far southeastern corner of the country.
Scientists have trekked to the remote location for decades to study the chimps’ remarkable use of tools.
They include the use of a stone hammer and anvil to crack open nuts — the most sophisticated act ever observed of humanity’s genetically closest relative.
But the number of chimps at Bossou has slumped to single figures.
The tribe is dying off and cannot be replenished by neighbouring chimp communities because forest destruction has left it isolated.
But after years of sad decline, there has been good news, said Aly Gaspard Soumah, director of the Bossou Environmental Research Institute.
Guides last week spotted the group’s last fertile female, Fanle, clutching a tiny baby on her belly, Soumah told AFP.
“There’s no doubt about it,” he said by phone.
“Three days ago we were able to confirm the (baby’s) sex using binoculars, because they were in the trees at the time — it’s a female.”
The Bossou apes have a unique relationship with the village population.
The animals live in the wild but share the territory and its resources with the locals, who protect the chimps, believing them to be the reincarnation of their ancestors.
Bossou is part of the Mount Nimba Strict Nature Reserve, a UNESCO-listed site located on the borders with Ivory Coast and Liberia that rises above the surrounding savannah.
The famous apes live in a forest of 320 hectares (790 acres).
But they are cut off from other chimps, on the slopes of Mount Nimba, by deforestation.
Locals practice a traditional slash-and-burn form of agriculture.
Until 2003, the number of Bossou chimps were relatively stable, with around 21 individuals, Soumah said.
But seven died of influenza in 2003, and others passed away in the following years, leaving just three adult males and four adult females before the latest birth.
Of these, three are aged over 60, while the youngest is an eight-year-old male. Fanle, aged in her 30s, is the last fertile female.
The big question now is about what to name her baby.
“We are going to invite prominent figures, the local authorities, partners we work with, to find one for her,” Soumah said.