Monkeys Share Stone Skills

Monkeys Share Stone Skills



March 2007 - Monkeys can learn skills 
from each other in the same way that humans do, according to a 
new study of capuchin monkeys in Brazil. While not conclusive, 
this research into the way monkeys use stones adds to a 
mounting body of evidence that suggests other species have 
something approaching human culture. 
Dr. Antonio Moura, a Brazilian researcher from the University 
of Cambridge Department of Biological Anthropology, has 
discovered signs that a group of capuchin monkeys in 
northeastern Brazil bang stones together as a signaling device 
to ward off potential predators. 
"One of the most interesting things is that they make a noise 
to scare off predators," Dr. Moura said. "They would seem to 
be communicating the danger to one another at the same time." 
A strong case has already been made for great apes, such as 
gorillas and chimpanzees, having a capacity for social 
learning, but until now there has been no evidence of such 
culture among the New World primates of Central or South 
America, including capuchins. 
Banging objects is an innate behavior in capuchin monkeys, but 
in all wild groups observed before this research the behavior 
had only happened in a foraging context. Banging stones is "an 
entirely new variant," Dr. Moura said. 
This research in the Serra da Capivara National Park, in the 
Piaui state of northeast Brazil. There Dr. Moura observed 
episodes of stone-banging among a group of 10 monkeys. 
Serra da Capivara National Park, a UNESCO World Heritage where 
ancient cave paintings have been found. 
As he approached, the monkeys would first search for a 
suitable loose stone, then hit it on a rock surface several 
times. 
At first, the act was apparently an aggressive one directed at 
Dr. Moura as a potential predator, and as the group became 
used to his presence in the area the stone-banging decreased. 
In many cases, adults and juvenile monkeys were seen banging 
the stones together without paying the researcher any 
attention at all. Dr. Moura says this suggests that the 
younger monkeys were learning the skill from their more 
experienced elders. 
Captive monkeys released into the area also appeared to learn 
to bang stones from the others. 
Dr. Moura describes this act of stone-banging as "a remarkable 
and novel" behavior which has yet to be observed in any other 
non-human primate species. 
Capuchin monkeys are found in Central America and middle South 
America, in Brazil, Ecuador, eastern Peru, and Paraguay). 

Biological anthropologists are divided over whether other 
species have the capacity to acquire skills by social 
learning, or whether the different skill sets exhibited by 
different groups of the same species are a result of 
environmental influences. 
In this case, Dr. Moura could find no environmental cause for 
the capuchins acquiring this skill, so he suggests that they 
had learned it by observing and imitating one another. 
"We already know that these monkey populations use stones as 
tools to dig holes or to forage and questions remain about why 
this happens in this area," Dr. Moura said. "Because it is 
quite dry and barren, it is possible they learn these skills 
from one another because they have to develop them quickly." 
As well as using the noise to deter predators, Dr. Moura also 
reports that in many cases the act of stone-banging, which 
often took place on higher ground, dislodged other stones that 
could hit the predator below. 
The main function of the act would appear to be that of a 
"loudspeaker," he said. Partly, this is to advise the predator 
that it has been spotted. 
Because the capuchins spread out widely in the dry forested 
areas of northeast Brazil when they forage, the noise could be 
an alarm call, he speculates. 
A capuchin monkey cracks a nut on an anvil using a large 
stone. 
This example of percussive stone technology adds to knowledge 
of other types of stone technology among wild capuchin monkeys 
of Brazil, such as the way they use stones as a hammer and 
anvil to crack nuts. 
In 2004, a team of researchers, led by University of Georgia 
psychologist Dr. Dorothy Fragaszy, published the first direct 
scientific report of tool use among a population of wild 
capuchin monkeys. The monkeys used stones as hammers to crack 
palm nuts on other anvil stones. There had been reports of 
single instances of this behavior but never before of a whole 
population using tools routinely over a long period of time. 
A multinational scientific research consortium including the 
University of Georgia, University of Sao Paulo, and the 
government of Italy has starting investigating this behavior 
with support grants from the National Geographic Society and 
the Leakey Foundation. 
The use of stones provides biological anthropologists with a 
rare example of primates using stone technology, adding to the 
archaeological record of primate behavior. Most items, such as 
sticks, used by primates in cases where they may be exhibiting 
socially-learned skills are perishable. 
Similar evidence of stone technology is found in the 
archaeological record of the earliest humans, and as more 
evidence emerges, scientists hope the ancient ancestry of 
human behavior will become clear. 





 

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