The chimpanzees of Bossou use a method of cracking nuts not recorded in any other non-human animals. Yet despite this sophistication, and unusually protective human neighbors, their numbers recently fell to just seven, most too old to breed. Now those trying to save them are delighted at the first healthy baby born to the Bossou chimps for eight years.
The Bossou troop of southeastern Guinea are spared some of the threats faced by their counterparts across central Africa. The inhabitants of the nearest village, also known as Bossou, revere them as the reincarnation of their ancestors and protect and share food with them. Scientists value the Bossou chimpanzees for a different reason; they crack nuts between a stone hammer and a stone anvil, a tool use advance not seen in almost any other wild population of our nearest living relatives.
Unfortunately, however, the forest in which the Bossou chimps live is small – 320 hectares (790 acres) – and almost entirely isolated from larger forest areas. To avoid interbreeding, adolescent chimpanzees disperse from their birth group. Over the years, some Bossou chimps have heard the call of more intact forests and made the dangerous journey across the surrounding savannah. None, however, have come the other way.
A mother chimp in Bossou tries to teach an earlier child to crack nuts, but the baby needs more time. ©ANC Productions Inc. and Primate Research Institute, Kyoto University
After numbering in the low 20s for many years, the Bossou chimps lost a third of their members to an outbreak of a respiratory disease in 2003. Besides being a reminder of the risks diseases like Covid-19 pose to great apes, this led to ground-breaking accounts of chimpanzee mothers caring for their dead children for weeks or months. The numbers have halved again since. Just one female of breeding age, Fanle, remains.
Tour guides have now reported Fanle clutching a baby, and even got close enough to confirm the child is another female.
When the news reached the village, "everyone, young and old, men and women, erupted in joy – the atmosphere was incredible," Aly Gaspard Soumah, director of the Bossou Environmental Research Institute, told AFP.
For 23 years, scientists, villagers, and conservationists have been working together to plant a tree corridor they hope will be wide enough to attract inhabitants of the larger nearby forested Nimba Mountains to Bossou. Hopefully, some of these will join the Bossou tribe and restore its viability, perhaps even learning double tool use in the process. There are plans to accelerate the tree planting in 2021.
If their nut-cracking is not a sufficient reason to love the Bossou chimps, the Bossou chimps have previously been observed getting drunk by shaping leaves to absorb sap the villagers tap from raffia palms. The sap ferments in the collecting containers, becoming 3-7 percent ethanol. Accounts of animals getting drunk on fermented fruit or even stealing cocktails are common. However, the construction of a tool to access alcohol is unprecedented, as is the fact scientists made a detailed study of how many standard drinks each chimp could handle.