Hook tool manufacture in New Caledonian crows: behavioural variation and the influence of raw materials.
Hook tool manufacture in New Caledonian crows: behavioural variation and the influence of raw materials.
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DOI：
10.1186/s12915-015-0204-7
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发表时间：
2015-11-18
期刊：
影响因子：
5.4
通讯作者：
Rutz C
中科院分区：
文献类型：
--
作者：
Klump BC;Sugasawa S;St Clair JJ;Rutz C
新喀里多尼亚乌鸦使用一系列觅食工具，并且是唯一已知能制作钩子的非人类物种。根据少量的观察，他们制造钩棒工具之前被描述为一个复杂的多阶段过程。工具行为是由遗传倾向、个人和社会学习和/或生态影响决定的，但理清这些因素的相对贡献仍然是一项重大的研究挑战。原材料的特性是工具制造行为变化的一个明显但在很大程度上被忽视的来源。我们对野生捕获的新喀里多尼亚乌鸦进行了实验，以评估其钩状棍子工具制造的变化，并研究原材料特性如何影响制造过程。在实验 1 中，我们发现新喀里多尼亚乌鸦制造钩状棒状工具的方式比之前想象的要复杂得多（18 名受试者使用 85 件工具），并且可能涉及两种新发现的行为：“拉动”以分离茎和弯曲工具轴。 Crows 的工具制造商差异很大：所采用的不同动作类型的数量；加工钩子和弯曲工具轴所花费的时间；以及处理序列的结构。在实验 2 中，我们研究了乌鸦与不同属性的原材料的相互作用，使用了一种新颖的范式，使我们能够确定受试者的排序偏好（7 名受试者 42 种工具）。植物特性受到影响：乌鸦选择茎的顺序；是否制造了钩状工具；发布基本工具所需的时间；以及可能的释放技术、行为动作的数量以及处理行为的方面。实验 2 的结果表明，实验 1 中观察到的自然行为变化至少部分是由于原材料特性的影响。我们对新颖制造行为的发现表明了新喀里多尼亚乌鸦钩状棍子工具制造的进化起源和逐步完善的合理情景。此外，我们对原材料特性与工具制造方面之间联系的实验证明，为解释在新喀里多尼亚乌鸦和一些灵长类动物中观察到的工具行为的区域差异提供了另一种假设。本文的在线版本 (doi:10.1186/s12915-015-0204-7) 包含补充材料，可供授权用户使用。
New Caledonian crows use a range of foraging tools, and are the only non-human species known to craft hooks. Based on a small number of observations, their manufacture of hooked stick tools has previously been described as a complex, multi-stage process. Tool behaviour is shaped by genetic predispositions, individual and social learning, and/or ecological influences, but disentangling the relative contributions of these factors remains a major research challenge. The properties of raw materials are an obvious, but largely overlooked, source of variation in tool-manufacture behaviour. We conducted experiments with wild-caught New Caledonian crows, to assess variation in their hooked stick tool making, and to investigate how raw-material properties affect the manufacture process. In Experiment 1, we showed that New Caledonian crows’ manufacture of hooked stick tools can be much more variable than previously thought (85 tools by 18 subjects), and can involve two newly-discovered behaviours: ‘pulling’ for detaching stems and bending of the tool shaft. Crows’ tool manufactures varied significantly: in the number of different action types employed; in the time spent processing the hook and bending the tool shaft; and in the structure of processing sequences. In Experiment 2, we examined the interaction of crows with raw materials of different properties, using a novel paradigm that enabled us to determine subjects’ rank-ordered preferences (42 tools by 7 subjects). Plant properties influenced: the order in which crows selected stems; whether a hooked tool was manufactured; the time required to release a basic tool; and, possibly, the release technique, the number of behavioural actions, and aspects of processing behaviour. Results from Experiment 2 suggested that at least part of the natural behavioural variation observed in Experiment 1 is due to the effect of raw-material properties. Our discovery of novel manufacture behaviours indicates a plausible scenario for the evolutionary origins, and gradual refinement, of New Caledonian crows’ hooked stick tool making. Furthermore, our experimental demonstration of a link between raw-material properties and aspects of tool manufacture provides an alternative hypothesis for explaining regional differences in tool behaviours observed in New Caledonian crows, and some primate species. The online version of this article (doi:10.1186/s12915-015-0204-7) contains supplementary material, which is available to authorized users.