Chimpanzees living in habitats with greater environmental variability are more likely to have a wide-ranging set of behaviours, according to a study published in the journal Nature Communications.
Since the behaviours include cultural traditions, variable environments could be a key driver of behavioural and cultural diversification in these great apes, one of our closest living relatives, says lead author Ammie Kalan, from Germany’s Max Planck Institute
“This is exciting,” she adds, “because environmental variability is one of the leading evolutionary factors thought to have contributed to our very own success as a species.”
Flexible behaviours and innovation help species adapt to unpredictable conditions. But until now, the authors say it’s been hard to show whether these are prompted by variable environmental conditions such as seasonal flux.
Nearly a decade of field data on behavioural diversity in chimpanzee (Pan troglodytes) communities across Equatorial Africa, contributed to by the “Pan African Program: The Cultured Chimpanzee”, offered an opportunity to investigate within a species.
Chimpanzee groups show a vast range and scope of behaviours in different contexts, such as communicating and foraging with various tools and regulating body temperature through bathing in pools or cooling down in caves.
Evidence suggests some of these behaviours are socially learned and thus evolved into cultural traditions, according to the group, which was also led by co-author Hjalmar Kühl.
They created a dataset from field work data at 46 temporary research sites across the wild chimpanzee range and a literature search and coded 31 different behaviours across 144 social groups.
They found that chimp groups in more variable habitats, recently and historically, were more likely to have a diverse set of behavioural traits. These environments included greater seasonality in rainfall and open savannahs versus more stable forest habitats.
Populations that lived further away from forest refuges during glacial cycles in the Pleistocene, around 2.5 million to 10,000 years ago, also had more diverse behaviours in their tool kit. This suggests those that moved away from the refuges were more likely to innovate for survival, according to the authors.
While it’s promising that the chimps’ diverse repertoire of behaviours helps them flexibly survive different and changing environments, Kalan notes there could be a limit.
“It’s important to keep in mind that today these habitats are changing at much too fast a rate with mainly human-induced destruction,” she says, “therefore this is an unprecedented time for chimpanzees and they are endangered in the wild.”