stone-tool-gracile supp 2 from Habitual stone-tool-aided extractive foraging in white-faced capuchins, Cebus capucinus

Habitual reliance on tool use is a marked behavioural difference between wild robust (genus Sapajus) and gracile (genus Cebus) capuchin monkeys. Despite being well studied and having a rich repertoire of social and extractive foraging traditions, Cebus sp. rarely use tools and have never been observed using stone tools. By contrast, habitual tool use by Sapajus is widespread. We review theory and discuss factors which might explain these differences in patterns of tool use between Cebus and Sapajus. We then report the first case of habitual stone tool use in a gracile capuchin: a population of white-faced capuchins (Cebus capucinus imitator) in Coiba National Park, Panama who habitually rely on hammerstone and anvil tool use to access structurally protected food items in coastal areas including Terminalia catappa seeds, hermit crabs, marine snails, terrestrial crabs and other items. This behaviour has persisted on one island in Coiba National Park since at least 2004. From 1 year of camera trapping, we found that stone tool use is strongly male-biased. Of the 205 camera trap days where tool use was recorded, adult females were never observed to use stone tools, although they were frequently recorded at the sites and engaged in scrounging behaviour. Stone tool use occurs year-round in this population; over half of all identifiable individuals were observed participating. At the most active tool use site, 83.2% of days where capuchins were sighted corresponded with tool use. Capuchins inhabiting the Coiba archipelago are highly terrestrial, under decreased predation pressure and potentially experience resource limitation compared to mainland populations—three conditions considered important for the evolution of stone tool use. White-faced capuchin tool use in Coiba National Park thus offers unique opportunities to explore the ecological drivers and evolutionary underpinnings of stone tool use in a comparative within- and between-species context.

习惯性依赖工具使用，是野生粗壮型悬猴属（Sapajus）与纤细型卷尾猴属（Cebus）卷尾猴之间显著的行为差异。尽管卷尾猴属（Cebus）物种已被广泛研究，且拥有丰富的社会行为与萃取觅食传统，但它们极少使用工具，且从未被观察到使用石制工具。与之形成鲜明对比的是，悬猴属（Sapajus）的习惯性工具使用行为分布广泛。我们首先梳理相关理论，并探讨可能解释卷尾猴属与悬猴属工具使用模式差异的各类因素。随后我们报告了首例纤细型卷尾猴的习惯性石制工具使用案例：位于巴拿马科伊巴国家公园的白面卷尾猴（Cebus capucinus imitator）种群，习惯性依赖锤砧式工具使用法，以获取沿海生境中结构保护性较强的食物资源，包括榄仁树（Terminalia catappa）种子、寄居蟹、海蜗牛、陆蟹及其他可食用物品。该行为至少自2004年起，便在科伊巴国家公园的一座岛屿上持续存在。通过为期1年的相机陷阱监测，我们发现石制工具使用行为存在显著的雄性偏向：在记录到工具使用行为的205个相机监测日中，从未观察到成年雌性使用石制工具，尽管它们频繁出现在工具使用位点并存在寄食行为。该种群的石制工具使用行为全年均可发生；超过半数的可识别个体曾被观察到参与此类行为。在活动最为频繁的工具使用位点，卷尾猴被目击的天数中，有83.2%对应工具使用行为。相较于大陆种群，科伊巴群岛的卷尾猴高度陆生、捕食压力较低，且可能面临资源限制——这三种条件被认为是石制工具使用演化的重要前置条件。因此，科伊巴国家公园内白面卷尾猴的工具使用行为，为在种内与种间的比较研究框架下探索石制工具使用的生态驱动因子与演化基础提供了独特的研究契机。