Strolling by way of the savanna-woodland panorama of Boé Nationwide Park, Guinea-Bissau, you would possibly encounter a tree coated in gnarled scars, with an accumulation of rocks surrounding its base.
The chimpanzees could have left the world, however you’re fortunate nonetheless, as a result of you’ve got stumbled upon proof of a uncommon — and probably cultural — chimpanzee conduct: accumulative stone throwing.
Video recordings present wild western chimpanzees, often grownup males, throwing rocks at particular bushes and repeatedly returning to these trees to perform the behavior.
[See video link after end of article.]
Whereas throwing, the chimpanzees pant hoot — a loud, long-distance communicative signal — and generally repeatedly hit their hands and feet on the tree in a conduct referred to as buttress drumming.
We now have simply returned from a subject web site in Guinea-Bissau the place we collected knowledge to assist us examine the social and ecological context of accumulative stone throwing to find out what these chimpanzees are attempting to speak.
Given our evolutionary relatedness to chimpanzees, we hope accumulative stone throwing can help us understand the emergence of complex communication and stone tool use over the course of human evolution.
A cultural conduct
Pant hooting and buttress drumming are each a part of the male chimpanzee show, suggesting that accumulative stone throwing would possibly characterize a modification of this frequent conduct. It is likely a cultural behavior on account of its restricted distribution, and since the provision of rocks and bushes doesn’t assure the presence of an accumulative stone throwing web site.
Earlier analysis means that accumulative stone throwing is probably going communicative or could actually have a symbolic goal, with websites marking necessary areas throughout the chimpanzees’ territory.
Nonetheless, we nonetheless don’t know what accumulative stone throwing websites would possibly imply to the chimpanzees themselves nor why they do it. Whereas some primates use stone instruments to entry meals, for example to crack open nuts, accumulative stone throwing is a uncommon instance of stone software use in a social context. It has been noticed in solely 4 chimpanzee teams in West Africa thus far.
Establishing camp
We traveled to the distant Boé chimpanzee territory in Guinea-Bissau and primarily based ourselves in Béli, a small village the place, in collaboration with native individuals, the Dutch non-governmental organization Chimbo maintains a compound. Visiting researchers and vacationers can keep right here and use a workspace with solar-generated electrical energy.
From Béli, we cycled and hiked 22 kilometers into the savanna-woodland to ascertain a bush camp with our two subject assistants, Djei Baldé and Balu Séra, and a grasp’s scholar from the Great Ape Behaviour Lab, Taylor Tippett.
The Boé chimpanzees performing the conduct are unhabituated; they will not be used to people, which means that we can not observe particular person chimpanzees on foot as a result of they’ll run away. As a substitute, we collected behavioral knowledge utilizing digital camera traps and recording gadgets.
We arrange two video cameras at every accumulative stone throwing web site and positioned the recording gadgets strategically to seize audio knowledge from the areas round these websites.
Our campsite bordered the Fefine, a big river that flows even in the dry season. In a panorama just like the savanna-woodland the place water sources are scarce, rivers just like the Fefine are necessary for wildlife and people alike. We captured a number of of our neighbors on cameras set up close to the riverbank.
Chimpanzee nests
On a mean day, we awakened round 6:30 a.m. and ate a small breakfast earlier than heading to a set of two to 5 websites. There, we changed the SD playing cards and batteries on the cameras, made positive the gadgets have been working properly and picked up any extra knowledge wanted, together with measurements of the tree and 3D scans of rocks thrown on the tree for later evaluation.
Alongside the way in which, we recorded observations of chimpanzee nests, feeding indicators, vocalizations and sightings.
The video and audio knowledge we collected will enable us to analyze the social traits of accumulative stone throwing, together with the age and intercourse of the stone thrower and the viewers (different chimpanzees close by who would possibly react to the throw). This data may help us decide what chimpanzees are attempting to speak.
We discovered that many of the websites first recognized by the Pan African Program, and revisited by our group in 2017, have been nonetheless in use throughout our latest journey to the sector, which means that chimpanzees can use these websites for over a decade.
The specter of bauxite mining
As many primate species face threats from human actions, cultural behaviors and the upkeep of wealthy cultural repertoires may help them adapt to environmental changes and provide support for conservation.
On prime of its potential communicative significance and intrinsic worth as a cultural conduct, accumulative stone throwing entails sturdy primate materials tradition, the lack of which might represent the erasure of primate heritage.
Sadly, chimpanzee habitat in Guinea-Bissau is threatened by extractive industries, notably industrial mining. Whereas within the subject, we encountered bore holes from bauxite mining exploration.
Bauxite mining represents a big alternative for economic growth and development in Guinea-Bissau. It may possibly additionally trigger habitat destruction and air pollution with extreme detrimental results for chimpanzees, different wildlife and the native individuals — because it already has in neighboring Guinea.
Environmental oversight and rules are a lot wanted, particularly given the added challenges of unstable governance in Guinea-Bissau.
By finding out and bringing consideration to chimpanzee cultural behaviors like accumulative stone throwing, we hope to help chimpanzee conservation and the maintenance of biodiversity more broadly, in addition to the preservation of primate cultural supplies for future analysis and training.
