Monkeys use tools to crack nuts, shuck oysters

Wild macaque monkeys use rocks to open nutshells and oyster shells. (AFP pic)

PARIS: Wild macaque monkeys have learnt to use tools to crack open nuts and even shuck oysters, researchers said on Wednesday, identifying a rare skillset long thought to exclusively belong to humans and chimpanzees.

Scientists from the UK and Thailand, where the native long-tailed macaque feeds on sea almonds, palm nuts, and the occasional bivalve, observed the monkeys using rocks for two distinct tasks.

Larger rocks, some weighing up to two kilogrammes (4.5 pounds), were used as a hammer to smash open nuts, while sharper stones formed knife-like levers to jimmy open prey such as oysters.

Before the study, conducted on  Thailand’s island of Piak Nam Yai, it was thought that only chimpanzees and bearded capuchins used stones to break open food in the wild.

Professor Tomos Proffitt, British Academy Postdoctoral Fellow at University College London, who wrote the study, said it could have wide relevance to primate studies.

“It contributes to our increasing understanding that not only apes and humans use tools for different tasks,” he told AFP.

“We should view macaques as highly intelligent problem solvers, in the same way that chimpanzees, capuchin monkeys are and early humans were also.”

Scientists in Brazil in 2016 observed wild-bearded capuchin monkeys hammering away at stones to create rough flakes similar to the tools first used by human forerunners.

But one of the macaques’ food sources, the oil palm, was only introduced to their island in the past few decades, meaning that the monkeys have learned to use tools to access its fruit for food extremely quickly, evolutionarily speaking.

“What we see is that they are adapting this stone tool use to other food sources away from the coast,” Proffitt said.

“In many cases of primate tool use these behaviours are learnt by youngsters through many years of observation and is not something that is genetically coded into them.”

The study was published in the journal Royal Society Open Science.