They say a bad worker blames his tools – but it’s hard to imagine a capuchin monkey using such an excuse. The crafty little monkeys of Boa Vista in Brazil are often seen using heavy rocks to crack open large palm nuts. Now, researchers say they are experts at choosing the best stones for the job.
In field experiments, Elisabetta Visalberghi of the Institute of Cognitive Sciences and Technologies in Rome, Italy, and colleagues have shown that the capuchins actually test their stone hammers before use.
If a monkey thinks one stone might not be up for the job of cracking the sturdy nuts – say, because it is too light or too likely to crumble – it will not waste time with it. Instead, the capuchin will move on and find another stone more suitable for the job.
Other than chimpanzees in western Africa, and a recently discovered group of long-tailed macaques, the capuchins of Boa Vista are the only non-human primates known to routinely use stones to crack open their dinner.