Wildlife researchers have witnessed and filmed startling habitual behaviour being exhibited by wild chimpanzees that suggests the animals are treating certain trees as ‘sacred’, in a similar way to early humans.
In rituals first noted in the Republic of Guinea, chimps were seen throwing rocks at a particular tree. In itself, this might seem unremarkable, but the action has no perceivable benefit to the animals whatsoever, and they repeat it time and time again, as detailed in a newly published report.
Writing for The Conversation, PhD researcher in wildlife conservation and land use at the Humboldt University of Berlin and report author, Laura Kehoe, describes how she was alerted to the phenomenon by a local guide while tracking a group of previously unstudied chimpanzees through the savannahs of the Republic of Guinea. The guide drew her attention to a series of markings on a tree trunk, and the team subsequently set up a camera trap to see what was making them.
‘What we saw on this camera was exhilarating,’ she explains. ‘A large male chimp approaches our mystery tree and pauses for a second. He then quickly glances around, grabs a huge rock and flings it full force at the tree trunk.’ They went on to discover more trees, some of which even had piles of rocks around or (in the case of some hollow trunks) inside them, which the group’s subsequent report said were ‘reminiscent of human cairns’.
‘Maybe we found the first evidence of chimpanzees creating a kind of shrine that could indicate sacred trees,’ writes Kehoe. ‘Indigenous West African people have stone collections at ‘sacred’ trees and such man-made stone collections are commonly observed across the world and look eerily similar to what we have discovered here.’
Chimps’ creative use of and sticks and stones has been recorded since Jane Goodall‘s groundbreaking field work in the 1960s, and the species is not alone in its employment of such tools—bearded capuchin monkeys in Brazil and long-tailed macaques in Thailand are known to use stone hammers to crack open shells and get at food, and various apes have previously been observed throwing rocks around to display their strength and gain influence or reinforce their position within a group—but this latest habitual behaviour has revealed something new to science.
The report describes how wild animals in 17 mid-to-long-term chimpanzee research sites, ‘habitually bang and throw rocks against trees, or toss them into tree cavities.’ Often, when the rock was thrown, the chimp would also let out a ‘pant hoot’ (vocal scream) and often begin drumming with its hands or feet on the tree.
Thus far, researchers have two main theories: either these antics form part of a male mate-seeking display, whereby the noise of the rock hitting a hollow tree increases the attractiveness of the animal (like a man showing off his brawn by using a hammer to ring a bell at a fairground strongman stall), or it is really ritualistic behaviour, which implies some sort of reverence for the so-called sacred trees.
When the group reported their findings, other researchers from around the region began setting up cameras and sending in videos of similar chimp behaviour. The ritualistic activity has been observed in parts of Guinea Bissau, Liberia and Côte d’Ivoire, yet it is certainly not thought to be universal, and nothing of the same nature has been seen any further east.
The chimp is our nearest living relative, and discoveries such as this underline the fact that we’re still a long way from understanding what really makes these animals tick. The most disturbing thing about that is, according to the Wild Chimpanzee Foundation there are fewer than 100,000 free-ranging chimpanzees left in the wild and, between deforestation, poaching and disease, some scientists believe the species will only survive for three more decades in the wild. If you’re interested in contributing to our understanding of our cousins, consider becoming a citizen scientist with www.chimpandsee.org.