Fragaszy Dorothy, Izar Patrícia, Visalberghi Elisabetta, Ottoni Eduardo B, de Oliveira Marino Gomes
Psychology Department, University of Georgia, Athens, GA 30602, USA.
Am J Primatol. 2004 Dec;64(4):359-66. doi: 10.1002/ajp.20085.
We conducted an exploratory investigation in an area where nut-cracking by wild capuchin monkeys is common knowledge among local residents. In addition to observing male and female capuchin monkeys using stones to pound open nuts on stone "anvils," we surveyed the surrounding area and found physical evidence that monkeys cracked nuts on rock outcrops, boulders, and logs (collectively termed anvils). Anvils, which were identified by numerous shallow depressions on the upper surface, the presence of palm shells and debris, and the presence of loose stones of an appropriate size to pound nuts, were present even on the tops of mesas. The stones used to crack nuts can weigh >1 kg, and are remarkably heavy for monkeys that weigh <4 kg. The abundance of shell remains and depressions in the anvil surface at numerous anvil sites indicate that nut-cracking activity is common and long-enduring. Many of the stones found on anvils (presumably used to pound nuts) are river pebbles that are not present in the local area we surveyed (except on or near the anvils); therefore, we surmise that they were transported to the anvil sites. Ecologically and behaviorally, nut-cracking by capuchins appears to have strong parallels to nut-cracking by wild chimpanzees. The presence of abundant anvil sites, limited alternative food resources, abundance of palms, and the habit of the palms in this region to produce fruit at ground level all likely contribute to the monkeys' routine exploitation of palm nuts via cracking them with stones. This discovery provides a new reference point for discussions regarding the evolution of tool use and material culture in primates. Routine tool use to exploit keystone food resources is not restricted to living great apes and ancestral hominids.
我们在一个地区进行了一项探索性调查，在那里，野生卷尾猴用石头敲开坚果的行为在当地居民中广为人知。除了观察雄性和雌性卷尾猴用石头在石头“砧座”上砸开坚果外，我们还对周边地区进行了调查，发现了猴子在岩石露头、巨石和原木（统称为砧座）上敲开坚果的实物证据。砧座的上表面有许多浅凹痕、棕榈壳和碎片，还有大小合适的可用来砸坚果的松散石头，即使在台地顶部也有砧座。用来敲开坚果的石头重量可能超过1千克，对于体重不足4千克的猴子来说，这些石头相当重。众多砧座地点的砧座表面有大量的壳残骸和凹痕，这表明敲坚果的活动很常见且持续时间很长。在砧座上发现的许多石头（大概是用来砸坚果的）是河卵石，在我们调查的当地地区（除了砧座上或附近）并不存在；因此，我们推测它们是被运到砧座地点的。从生态和行为角度来看，卷尾猴敲坚果的行为似乎与野生黑猩猩敲坚果的行为有很多相似之处。大量砧座地点的存在、有限的替代食物资源、丰富的棕榈树以及该地区棕榈树在地面结果的习性都可能促使猴子通过用石头砸开坚果来常规性地获取棕榈坚果。这一发现为有关灵长类动物工具使用和物质文化进化的讨论提供了一个新的参考点。利用关键食物资源进行常规工具使用并不局限于现存的大型猿类和原始人类。
