Factors affecting cashew processing by wild bearded capuchin monkeys (Sapajus libidinosus, Kerr 1792)

Abstract

Cashew nuts are very nutritious but so well defended by caustic chemicals that very few species eat them. We investigated how wild bearded capuchin monkeys (Sapajus libidinosus) living at Fazenda Boa Vista (FBV; Piauí, Brazil) process cashew nuts (Anacardium spp.) to avoid the caustic chemicals contained in the seed mesocarp. We recorded the behavior of 23 individuals toward fresh (N = 1282) and dry (N = 477) cashew nuts. Adult capuchins used different sets of behaviors to process nuts: rubbing for fresh nuts and tool use for dry nuts. Moreover, adults succeed to open dry nuts both by using teeth and tools. Age and body mass significantly affected success. Signs of discomfort (e.g., chemical burns, drooling) were rare. Young capuchins do not frequently closely observe adults processing cashew nuts, nor eat bits of nut processed by others. Thus, observing the behavior of skillful group members does not seem important for learning how to process cashew nuts, although being together with group members eating cashews is likely to facilitate interest toward nuts and their inclusion into the diet. These findings differ from those obtained when capuchins crack palm nuts, where observations of others cracking nuts and encounters with the artifacts of cracking produced by others are common and support young individuals' persistent practice at cracking. Cashew nut processing by capuchins in FBV appears to differ from that observed in a conspecific population living 320 km apart, where capuchins use tools to open both fresh and dry nuts. Moreover, in the latter population, chemical burns due to cashew caustic compounds appear to be common. The sources of these differences across populations deserve investigation, especially given that social influences on young monkeys learning to open cashew nuts at FBV seem to be nonspecific. Am. J. Primatol. 78:799-815, 2016. © 2016 Wiley Periodicals, Inc.

Cashew Nut Positioning during Stone Tool Use by Wild Bearded Capuchin Monkeys (Sapajus libidinosus)

“…We know that cashew nut processing with stone tools is present in at least 1 other population of capuchins, at Fazenda Boa Vista [Visalberghi et al, 2016], but we do not currently know whether this variant of positioning is present in this or other capuchin populations that use stone tools to process cashew nuts. Another factor not analysed here is whether different types of anvil materials or inclinations could elicit different frequencies of positioning styles.…”

“…In Fazenda Boa Vista, capuchins process fresh cashew nuts by rubbing them on an abrasive surface, but use stone tools to crack open dry cashews [Visalberghi et al, 2016]. Conversely, capuchins from Serra da Capivara National Park (SCNP) use stone tools to open both fresh and dry nuts .…”

“…Chimpanzees in West Africa ( Pan troglodytes verus ) use percussive wooden and stone tools to crack open nuts [Boesch and Boesch, 1983;by Capuchin Monkeys 393 Folia Primatol 2016;87:392-397 DOI: 10.1159/000459621 Koops et al, 2010;Sirianni et al, 2015]; Burmese long-tailed macaques ( Macaca fascicularis aurea ) use stones to process shellfish, nuts and other prey [Malaivijitnond et al, 2007;Gumert and Malaivijitnond, 2012], and capuchin monkeys ( Sapajus spp.) use percussive stone tools to process palm nuts [Fragaszy et al, 2004;Ottoni and Izar, 2008;Spagnoletti et al, 2011], cashew nuts [Sirianni and Visalberghi, 2013;Falótico and Ottoni, 2016;Visalberghi et al, 2016], and to access hidden resources [Mannu and Ottoni, 2009].…”

Percussive tool use by Taï Western chimpanzees and Fazenda Boa Vista bearded capuchin monkeys: a comparison

“…The monkeys can open the dry cashew nuts either with their teeth or with tools [4,25]. In this case, tool use serves to open the nut without exposing the hands or mouth to the caustic resin present in the shell [48].…”

“…One year of behavioural observations indicate that the vast majority of tool-use episodes occur on anvils located on the ground (boulders or logs), and only 1% of the episodes (seven palm nuts and two other encased food items) on tree branches [39]. Tree branches are used as anvils in 16% of the episodes in which dry cashew nuts are cracked [48].…”