Meeting Abstract
Tool use is not unique to humans; a few wild populations of nonhuman animal species use tools as well. While channeling the organization of movements as per task demands is a defining feature of tool use in humans, we lack information about this aspect of tool use in nonhuman animals as quantifying movements under free-ranging conditions is usually difficult. In the present study, we analyzed how wild bearded capuchin monkeys, Sapajus libidinosus organize their movements when using anvil-and-hammer tools to hit a piaçava palm nut. They mostly use the lower back, hip, and knee, with only limited movement of the elbow, shoulder, and wrist. Their tendency to rely on the movement of the hind limbs and trunk increases as hammer mass increases in relation to the body. They organize their movements to maintain the velocity of the hammer at the moment of impact (a first order parameter) rather than maintaining the kinetic energy of the hammer (a second order parameter) as humans do. In this way, although relatively inefficient, wild bearded capuchin monkeys have developed a skillful method to meet the demands of the nut-cracking task.
