University of Tübingen: Orangutans spontaneously use a mallet to crack nuts

The cracking of nuts with an object used as a hammer is considered to be one of the most complex tool uses in the animal kingdom. So far, only chimpanzees, capuchin monkeys and macaques have been seen cracking nuts with such tools in the wild. Dr. Elisa Bandini and Dr. Claudio Tennie from the Older Prehistory and Quaternary Ecology of the University of Tübingen examined in a new study. Of twelve orangutans living in zoos, four spontaneously and successfully used the hammers offered for this purpose, although they could not learn this behavior from others. The study is published in the American Journal of Primatology .

“After chimpanzees, the orangutans are the great apes with the second largest repertoire of known tool use. So far, however, wild animals have not been observed cracking nuts, ”says Claudio Tennie. In the new study, four orangutans at the Leipzig Zoo who had not been shown this behavior were given hard nuts, sections of branches as hammers and a block of wood that could serve as an anvil.

Successful without a role model
An orangutan first used the anvil as a hammer. In later experiments this was attached, whereupon the animal spontaneously used the mallet to crack a nut. However, the other three older orangutans tried their hands or teeth. “Biting up really worked with these three animals,” reports Tennie.

In their analysis, the researchers included a similar study from Zurich Zoo with eight orangutans, which was previously unpublished. Of the total of twelve orangutans tested, four individuals, one in Leipzig and three in Zurich, spontaneously and inexperienced began to crack nuts with wooden hammers. “The orangutans can even develop this complex behavior purely through individual learning,” says Elisa Bandini. So cracking nuts with tools is – at least in the case of orangutans – behavior that does not require cultural transmission through copying. “Up to now, science had assumed the opposite assumption and had even expected that the skill would become extinct in great apes if it could not be passed on culturally.”