Why do chimpanzees throw stones at trees?
Why do chimpanzees throw stones at trees?
Newly discovered stone tool-use behavior and accumulation sites in wild chimpanzees reminiscent to human cairns
February 29, 2016
Chimpanzees often use tools to extract or consume food. Which tools they choose for which purpose, however, can differ depending on the region where they live. Researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have thus initiated the ‘Pan African Programme: The Cultured Chimpanzee’ and, since 2010, have collected data on chimpanzee behavior, demography and resource availability across Africa following a standardized protocol. This is how the researchers encountered a thus far unknown behavior: In West Africa chimpanzees throw stones at trees resulting in conspicuous accumulations at these sites. Why exactly the animals do this the researchers do not yet know, yet the behavior appears to have some cultural elements.
This link goes to the Max Plank Institute in Germany
Mysterious stone piles under trees are the work of chimpanzees.
Chimpanzees have been studied for almost 60 years at a few long-term field sites, which are mainly located in East and West Africa. They are proficient tool-users, using sticks to fish for termites, to dip for ants, to extract honey, and even using stone or wooden hammers to crack open nuts. Outside the foraging context male chimpanzees sometimes throw branches and stones during displays, or leaf-clip to solicit sex from females. This research has therefore been fundamental for providing insights into natural chimpanzee behavior and most importantly into the differences between populations. However, at the same time it has also become clear that chimpanzee behavior observed at such a small number of sites is unlikely to be representative of other chimpanzee populations.
In an effort to overcome this limitation, researchers of the Department of Primatology at the Max Planck Institute for Evolutionary Anthropology have initiated the ‘Pan African Programme: The Cultured Chimpanzee’ (PanAf) to better understand the ecological and evolutionary drivers of behavioral diversification in chimpanzees. Following a unique standardized protocol, data on chimpanzee behavior, demography and resource availability have been collected since 2010 at 39 different temporary research sites across Africa. “The PanAf project represents a new approach to studying chimpanzees and will provide many interesting insights into chimpanzee demography and social structure, genetics, behavior and culture”, says Hjalmar Kuehl of the Max Planck Institute for Evolutionary Anthropology and the German Centre for Integrative Biodiversity Research. “The Pan Af is only possible due to the numerous collaborations with chimpanzee researchers, field workers and national wildlife authorities in 14 countries across Africa”. Since chimpanzees were not habituated to human presence at these sites, the researchers rely on a wide spectrum of non-invasive sampling methods, including remote camera traps.
http://www.mpg.de/10328790/chimpanzee-stone-tree
Stone-throwing chimps leave scientists stumped by ‘sacred shrine’
Chimpanzees in Guinea and the forests of Liberia have been observed picking up stones and throwing them at a tree as well as placing them gently at the base - behaviour that appeared to serve no purpose and could be evidence of "ritualistic behaviour" in animals.
"What we saw on this camera was exhilarating – 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," said Laura Kehoe, PhD researcher at Humboldt University of Berlin.
The German primatologist, whose team discovered the odd behaviour, said that the practice "could be a ritual ... This would be the first evidence of ritualistic behaviour in animals."
In a paper published in the journal Nature Scientific Reports the researchers suggested two possible explanations: "The behaviour could be part of a male display" or "it could be more symbolic than that."
In the first case the loud noise made by the rock hitting a tree could "add to the impressive nature of a display".
With video:
http://www.telegraph.co.uk/news/science/science-news/12182951/Stone-throwing-chimps-leave-scientists-stumped-by-sacred-shrine.html
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