Which New World monkey uses stone hammers and anvils to crack open nuts?

The bearded capuchin uses stone hammers and anvils to crack open nuts and other hard fruits. Also called the black-striped capuchin, Sapajus libidinosus lives mainly in the dry forests, savannas, and Caatinga landscapes of Brazil.

The monkey places a nut on a flat stone or a natural hollow in a rock, then strikes it with a selected hammerstone. The anvil holds the nut steady while the hammer delivers the force needed to break its shell. Capuchins may transport both nuts and stones to favored cracking sites, where repeated use leaves cracked shells, discarded fragments, and pitted anvil surfaces.

This is more than a one-off trick. Young monkeys gradually learn the technique through observation and practice, and populations can differ in the foods they process and the stones they prefer. Some hammerstones weigh more than a kilogram, a substantial load for a monkey weighing only a few kilograms.

The main mix-up is taxonomy: “bearded capuchin” is a common name for the black-striped capuchin, whose scientific name has changed from Cebus libidinosus to Sapajus libidinosus in modern classifications. Other capuchin species also use tools, but this species is particularly famous for hammer-and-anvil nut cracking.