Abstract

The use of pounding stone tools (PSTs) is a customary behaviour in several wild populations of capuchin monkeys; most of these monkeys use PSTs primarily to open hard palm nuts. Here, we describe the use of PSTs in two not previously studied groups of capuchin monkeys ( Sapajus libidinosus ) in Serra da Capivara National Park (SCNP), northeastern Brazil, and compare them to other groups and populations. Capuchins from SCNP are one of the only known population that habitually use PSTs for several purposes other than nut processing, including cracking seeds and fruits, breaking and/or enlarging holes in tree trunks or rocks, and pulverizing pebbles. Moreover, they use PSTs sequentially with probe stick tools to access hidden prey. The average size of PSTs was larger than the average locally available stones, suggesting active choice. The two groups exhibited more diversity in the use of PSTs than any other known population to date.