A study published this week in the Science journal shows that the diversity of behaviour of chimpanzees is poorer when in contact with humans.
Chimpanzees have, over the centuries, developed their own culture. Tools to catch their food, a way of communicating, this is all transmitted from generation to generation in primates and this is often enriched over time.
As with humans, the social and cultural behaviours of chimpanzees are important for each animal to be integrated into a community. Moreover, according to the geographical origin of great apes, their ways of doing things can be different.
Under pressure from humans
But chimpanzees are currently under pressure from humans, who are encroaching more and more on their territory. And when their habitat is gradually occupied by humans, populations decline, as do their cultural variations.
A team of researchers from around the world studied 144 different chimpanzee communities in 17 countries in equatorial Africa. Scientists focused on behaviours that are not innate in monkeys and can therefore vary from one community to another.
Their methods of finding food are different. Where some will plunge a stick of wood into a tree trunk to capture ants, others have learned how to crack nuts open.
Cultural diversity declining
The results are alarming: in areas where chimpanzees are most impacted by humans, diversity is reduced by 88%. Human activity thus disrupts the lives of monkeys, who develop fewer specific behaviours.
The hypotheses of explanations are multiple. Because chimpanzees are hunted for meat, they may be reluctant to use long distance screams or other noisy means of communication, such as kicking tree trunks, to communicate. This so as not to be spotted.
Similarly, chimpanzees near humans have shown an ability to adapt by going to feed where their neighbours are living. This is not without risk since the peasants do not hesitate to kill the monkeys who come too close to their homes.
The establishment of sanctuaries?
How is this a problem? After all, there is no connection between the cultural diversity of chimpanzees and their ability to survive in the wild. Nevertheless, the risk is that human pressure will reduce the ability of monkeys to adapt to their environment.
When scientists discover a new group of chimpanzees, it is not uncommon for them to have practices that are very different from those we have known in the past. And it remains difficult to measure the loss, for chimpanzees, that can lead to such a cultural decline.
The authors of the study request the establishment of ‘cultural heritage sites for chimpanzees,’ areas where humans could not come into contact with the monkeys. A concept that could also be put in place with orangutans, for whom a great cultural diversity has also been observed.
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