Corvus moneduloides

Abstract: TOOL behaviour in wild birds has been described as mostly stereotyped1,2, and tool manufacture involves little modification of material3–5. Here I report in New Caledonian crows Corvus moneduloides the manufacture and use of two different types of hook tool to aid prey capture: hooked-twig and stepped-cut barbed pandanus leaf. Crow tool manufacture had three features new to tool use in free-living nonhumans: a high degree of standardization, distinctly discrete tool types with definite imposition of form in tool shaping, and the use of hooks. These features only first appeared in the stone6 and bone7 tool-using cultures of early humans after the Lower Palaeolithic6,7, which indicates that crows have achieved a considerable technical capability in their tool manufacture and use.

Abstract: We present an experiment showing that New Caledonian crows are able to choose tools of the appropriate size for a novel task, without trial-and-error learning. This species is almost unique amongst all animal species (together with a few primates) in the degree of use and manufacture of polymorphic tools in the wild. However, until now, the flexibility of their tool use has not been tested. Flexibility, including the ability to select an appropriate tool for a task, is considered to be a hallmark of complex cognitive adaptations for tool use. In experiment 1, we tested the ability of two captive birds (one male, one female), to select a stick (from a range of lengths provided) matching the distance to food placed in a horizontal transparent pipe. Both birds chose tools matching the distance to their target significantly more often than would be expected by chance. In experiment 2, we used a similar task, but with the tools placed out of sight of the food pipe, such that the birds had to remember the distance of the food before selecting a tool. The task was completed only by the male, who chose a tool of sufficient length significantly more often than chance but did not show a preference for a matching length.

Abstract: The use of twigs by these birds to coax out hidden food seems to be an instinctive skill. New Caledonian crows make a variety of tools in the wild. They will remove leaves and side branches from a twig and use it to gather food, for instance. New experiments show that young hand-raised New Caledonian crows make and use tools without prior contact with adult crows and with no instruction from humans. This suggests that the skills of wild crows are not socially acquired. Social input may be involved in transmitting specific tool shapes or techniques, however, as young crows pay close attention to tool use by their human foster parents. The crow's use of tools in this way is a good model for the study of interactions between inherited traits and social or individual learning. New Caledonian crows (Corvus moneduloides) are the most prolific avian tool-users1,2. Regional variation in the shape of their tools may be the result of cumulative cultural evolution3 — a phenomenon considered to be a hallmark of human culture4. Here we show that hand-raised juvenile New Caledonian crows spontaneously manufacture and use tools, without any contact with adults of their species or any prior demonstration by humans. Our finding is a crucial step towards producing informed models of cultural transmission in this species, and in animals in general.

Abstract: Previous observations of a New Caledonian crow (Corvus moneduloides) spontaneously bending wire and using it as a hook [Weir et al. (2002) Science 297:981] have prompted questions about the extent to which these animals ‘understand’ the physical causality involved in how hooks work and how to make them. To approach this issue we examine how the same subject (“Betty”) performed in three experiments with novel material, which needed to be either bent or unbent in order to function to retrieve food. These tasks exclude the possibility of success by repetition of patterns of movement similar to those employed before. Betty quickly developed novel techniques to bend the material, and appropriately modified it on four of five trials when unbending was required. She did not mechanically apply a previously learned set of movements to the new situations, and instead sought new solutions to each problem. However, the details of her behaviour preclude concluding definitely that she understood and planned her actions: in some cases she probed with the unmodified tools before modifying them, or attempted to use the unmodified (unsuitable) end of the tool after modification. Gauging New Caledonian crows’ level of understanding is not yet possible, but the observed behaviour is consistent with a partial understanding of physical tasks at a level that exceeds that previously attained by any other non-human subject, including apes.