Manual skills for processing plant underground storage organs by wild bearded capuchins

Abstract

Objectives: Wild Sapajus libidinosus exploit underground storage organs (USOs) that require extraction and extensive processing before consumption. Since capuchin monkeys are small-sized extractive foragers that cannot perform forceful precision grips, we expected that: (a) they would use other body parts together with their hands, (b) older (and larger) capuchins would be more efficient than younger (and smaller) ones, and (c) capuchins would invest greater effort/time to exploit USOs than other foods. Materials and Methods:We recorded 178 episodes of USO processing performed by 20 individuals. The behavior was videotaped and scored frame-by-frame.Results: We identified six sequential stages of processing: Excavation, extraction, soil removal, transport, peeling, and fragmenting the inner tissues. Capuchins made frequent use of forceful hand postures and manipulation in which the hands were strongly supported by other body parts, principally the mouth. Older capuchins were more efficient than younger individuals in pulling the USOs out of the ground. Finally, exploiting USOs was time-consuming, lasting more than 4 min per item, on average.Discussion: Despite having smaller body-mass and greater manual constraints than catarrhine extractive foragers, capuchins, even smaller individuals, mastered USO processing thanks to their behavioral flexibility and persistence. Our findings reveal that precision grips are not essential for forceful actions during complex food processing and that, unlike catarrhines, capuchins, especially adults, rarely use thumb opposition during forceful grasping of food. In contrast, extended sustained attention and varied manual behavior appear to be convergent features of platyrrhine and catarrhine extractive foragers. K E Y W O R D Sdigging behavior, extractive foraging, manual dexterity, USOs, Sapajus libidinosus

Positional behavior and substrate use in wild adult bearded capuchin monkeys (Sapajus libidinosus)

“…Our last two predictions link the use of terrestrial substrates with diet and bipedal behavior. The capuchins at FBV, and other sites, have been the subject of several previous studies focused on the use of stone hammers to crack palm nuts (e.g., Visalberghi & Fragaszy, ), their use of other foods found on the ground that are difficult to access and to process (Chalk et al, ; Spagnoletti et al, ; Truppa et al, ; Wright et al, ), and their bipedal behavior when they transport stones and use them to crack nuts (Duarte, Hanna, Sanches, Liu, & Fragaszy, ; Falótico, Inaba, McGrew, & Ottoni, ; Hanna et al, ; Visalberghi et al, ). We predicted that monkeys would move bipedally primarily during transport of objects (such as nuts and hammer stones) and stand bipedally during nut‐cracking.…”

“…These behaviors primarily occur on the ground (Visalberghi & Fragaszy, ) and elicit bipedal behavior during transport of materials and during the strike (Liu et al, ; Massaro, Massa, Simpson, Fragaszy, & Visalberghi, ). They also collect many foods found on the ground or extracted from the ground (i.e., underground plant storage organs; Chalk et al, ; Spagnoletti et al, ; Truppa, Marino, Izar, Fragaszy, & Visalberghi, ; Visalberghi et al, ; Wright et al, ).…”

Anticipating future actions: Motor planning improves with age in wild bearded capuchin monkeys (Sapajus libidinosus)

“…Capuchins' ancestral lineage diverged 30–40 million years ago from that of the other haplorrhine primates, humans included (Schrago & Russo, 2003). Capuchins improve their locomotor skills rapidly once they begin to spend time off the mother around three months of age (Fragaszy et al, 2004), yet their proficiency in exploiting hard‐to‐process foods, which require strength and/or fine hand movements, develops over years (e.g., Eadie, 2015; Fragaszy & Adams‐Curtis, 1997; Gunst et al, 2010; Truppa et al, 2019; Truppa et al, 2019; Visalberghi et al, 2016). We expected that infant capuchins, which were independent enough from their mother to participate in our study, would show motor anticipation, as 19‐month‐old human infants do (McCarty et al, 1999).…”

The art of snacking: Innovative food extraction in a synanthropic species is associated with food exposure and food categorization

“…Most studies on extractive foraging in primates have either documented extractive foraging in naturalistic settings with natural food items (e.g. shellfish cracking in long-tailed monkey, Gumert & Malaivijitnond, 2012; walnut ‘processing’ in Japanese macaques, Tamura, 2020; plant underground storage organ ‘processing’ in capuchin, Truppa et al, 2019) or have employed artificial extraction tasks in captive (e.g. Crast et al, 2010; Kendal et al, 2015) and non-captive settings (e.g.…”