Optional tool use: The case of wild bearded capuchins (Sapajus libidinosus) cracking cashew nuts by biting or by using percussors

Abstract

Tool use in humans can be optional, that is, the same person can use different tools or no tool to achieve a given goal. Strategies to reach the same goal may differ across individuals and cultures and at the intra‐individual level. This is the first experimental study at the intra‐individual level on the optional use of a tool in wild nonhuman primates. We investigated optional tool use by wild bearded capuchins (Sapajus libidinosus) of Fazenda Boa Vista (FBV; Piauí, Brazil). These monkeys habitually succeed in cracking open the mesocarp of dry cashew nuts (Anacardium spp.) by pounding them with stones and/or by biting. We assessed whether availability of a stone and resistance of the nut affected capuchins' choice to pound or to bite the nuts and their rates of success. Sixteen capuchins (1–16 years) received small and large dry cashew nuts by an anvil together with a stone (Stone condition) or without a stone (No‐Stone condition). In the Stone conditions, subjects used it to crack the nut in 89.1% (large nuts) and 90.1% (small nut) of the trials. Nut size significantly affected the number of strikes used to open it. Availability of the stone significantly increased the average percent of success. In the No‐Stone conditions, monkeys searched for and used other percussors to crack the nuts in 54% of trials. In all conditions, age affects percentage of success and number of strikes to reach success. We argue that exclusive use of stones in other sites may be due to the higher abundance of stones at these sites compared with FBV. Since capuchins opened cashews with a tool 1–2 years earlier than they succeed at cracking more resistant palm nuts, we suggest that success at opening cashew nuts with percussors may support the monkeys' persistent efforts to crack palm nuts.

Stone tools differences across three capuchin monkey populations: food’s physical properties, ecology, and culture

“…More recently, the population of S. libidinosus of Serra das Confusões National Park (SCoNP), 100 km from SCaNP, was described to use stone tools to process encased food, exploring different resources ( Buchenavia nuts), or on different frequencies ( Attalea nuts, Hymenaea pods), from other populations 6 . Another well-studied population of S. libidinosus is from Fazenda Boa Vista (FBV), where the monkeys appear to be specialized in cracking open hard resistant palm nuts 10 , 25 , although they also occasionally process less resistant food 26 , using lighter stone tools 10 . Other populations of S. libidinosus have been described to use stone tools to process encapsulated, hard-to-break food resources 7 , 8 .…”

Effects of food material properties and embedded status on food processing efficiency in bearded capuchins

“…In addition, robust capuchins ( Sapajus spp.) exhibit masticatory adaptations that further enhance their ability to access embedded foods encased in mechanically challenging tissues (Daegling, 1992; Kay, 1981; Masterson, 1996; Taylor & Vinyard, 2009; Wright, 2005; Wright et al, 2009), or chemically challenging tissues (Visalberghi et al, 2016; Visalberghi, Barca, Izar, Fragaszy, & Truppa, 2021) and thereby increase their diet breadth. Capuchins begin to practice extractive food processing techniques early in development.…”

Açai Berry Attenuates Cyclophosphamide-Induced Damage in Genitourinary Axis-Modulating Nrf-2/HO-1 Pathways

“…The scientific community has been increasingly supporting the idea that food can serve as medicine and that diets high in plant foods and low in processed foods can prevent or reduce the severity of many diseases [ 19 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. It is imperative to carry out research to identify natural substances that can potentially protect against CYP-induced oxidative stress while also lowering chemotherapy-related toxicity.…”