Publications

lateralization of tool use in new caledonian crows (corvus moneduloides).	we studied laterality of tool use in 10 captive new caledonian (nc) crows (corvus moneduloides). all subjects showed near-exclusive individual laterality, but there was no overall bias in either direction (five were left-lateralized and five were right-lateralized). this is consistent with results in non-human primates, which show strong individual lateralization for tool use (but not for other activities), and also with observations of four wild nc crows by rutledge & hunt. jointly, these resul ...	2004	15504013
parallel tool industries in new caledonian crows.	individual specialization in the use of foraging tools occurs in hunter-gatherer societies but is absent in non-human primate tool use. 'parallel tool industries' in hunter-gatherers are mainly based on strict sexual division of labour that is highly reliant on social conformity. here, we show that 12 individuals in a population of new caledonian crows on maré island had strong preferences for either stick tools or pandanus tools. eight of the 12 crows had exclusive preferences. the individual s ...	2007	17284404
tool use by wild new caledonian crows corvus moneduloides at natural foraging sites.	new caledonian crows corvus moneduloides use tools made from sticks or leaf stems to 'fish' woodboring beetle larvae from their burrows in decaying wood. previous research on this behaviour has been confined to baited sites, leaving its ecological context and significance virtually unexplored. to obtain detailed observations of natural, undisturbed tool use, we deployed motion-triggered video cameras at seven larva-fishing sites. from 1797 camera hours of surveillance over 111 days, we recorded ...	2010	20053646
activity profiles and hook-tool use of new caledonian crows recorded by bird-borne video cameras.	new caledonian crows are renowned for their unusually sophisticated tool behaviour. despite decades of fieldwork, however, very little is known about how they make and use their foraging tools in the wild, which is largely owing to the difficulties in observing these shy forest birds. to obtain first estimates of activity budgets, as well as close-up observations of tool-assisted foraging, we equipped 19 wild crows with self-developed miniature video cameras, yielding more than 10 h of analysabl ...	2015	26701755
new caledonian crows attend to multiple functional properties of complex tools.	the ability to attend to the functional properties of foraging tools should affect energy-intake rates, fitness components and ultimately the evolutionary dynamics of tool-related behaviour. new caledonian crows corvus moneduloides use three distinct tool types for extractive foraging: non-hooked stick tools, hooked stick tools and tools cut from the barbed edges of pandanus spp. leaves. the latter two types exhibit clear functional polarity, because of (respectively) a single terminal, crow-man ...	2013	24101625
restricted gene flow and fine-scale population structuring in tool using new caledonian crows.	new caledonian crows corvus moneduloides are the most prolific avian tool users. it has been suggested that some aspects of their complex tool use behaviour are under the influence of cultural processes, involving the social transmission-and perhaps even progressive refinement-of tool designs. using microsatellite and mt-haplotype profiling of crows from three distinct habitats (dry forest, farmland and beachside habitat), we show that new caledonian crow populations can exhibit significant fine ...	2012	22418860
the evolutionary origins and ecological context of tool use in new caledonian crows.	new caledonian (nc) crows corvus moneduloides are the most prolific avian tool users. in the wild, they use at least three distinct tool types to extract invertebrate prey from deadwood and vegetation, with some of their tools requiring complex manufacture, modification and/or deployment. experiments with captive-bred, hand-raised nc crows have demonstrated that the species has a strong genetic predisposition for basic tool use and manufacture, suggesting that this behaviour is an evolved adapta ...	2012	22209954
extraordinary large brains in tool-using new caledonian crows (corvus moneduloides).	a general correlation exists between brain weight and higher cognitive ability in birds and mammals. in birds this relationship is especially evident in corvids. these animals are well-known for their flexible behavior and problem-solving abilities, and have relatively large brains associated with a pallial enlargement. at the behavioral level, new caledonian crows stand out amongst corvids because of their impressive object manipulation skills both in the wild and in the laboratory. however, no ...	2008	18262356
the crafting of hook tools by wild new caledonian crows.	the 'crafting' of tools involves (i) selection of appropriate raw material, (ii) preparatory trimming and (iii) fine, three-dimensional sculpting. its evolution is technologically important because it allows the open-ended development of tools. new caledonian crows manufacture an impressive range of stick and leaf tools. we previously reported that their toolkit included hooked implements made from leafy twigs, although their manufacture had never been closely observed. we describe the manufactu ...	2004	15101428
did tool-use evolve with enhanced physical cognitive abilities?	the use and manufacture of tools have been considered to be cognitively demanding and thus a possible driving factor in the evolution of intelligence. in this study, we tested the hypothesis that enhanced physical cognitive abilities evolved in conjunction with the use of tools, by comparing the performance of naturally tool-using and non-tool-using species in a suite of physical and general learning tasks. we predicted that the habitually tool-using species, new caledonian crows and galápagos w ...	2013	24101628
hook tool manufacture in new caledonian crows: behavioural variation and the influence of raw materials.	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 ...	2015	26582537
of babies and birds: complex tool behaviours are not sufficient for the evolution of the ability to create a novel causal intervention.	humans are capable of simply observing a correlation between cause and effect, and then producing a novel behavioural pattern in order to recreate the same outcome. however, it is unclear how the ability to create such causal interventions evolved. here, we show that while 24-month-old children can produce an effective, novel action after observing a correlation, tool-making new caledonian crows cannot. these results suggest that complex tool behaviours are not sufficient for the evolution of th ...	2014	24920476
using the aesop's fable paradigm to investigate causal understanding of water displacement by new caledonian crows.	understanding causal regularities in the world is a key feature of human cognition. however, the extent to which non-human animals are capable of causal understanding is not well understood. here, we used the aesop's fable paradigm--in which subjects drop stones into water to raise the water level and obtain an out of reach reward--to assess new caledonian crows' causal understanding of water displacement. we found that crows preferentially dropped stones into a water-filled tube instead of a sa ...	2014	24671252
an end to insight? new caledonian crows can spontaneously solve problems without planning their actions.	animals rarely solve problems spontaneously. some bird species, however, can immediately find a solution to the string-pulling problem. they are able to rapidly gain access to food hung on the end of a long string by repeatedly pulling and then stepping on the string. it is currently unclear whether these spontaneous solutions are produced by insight or by a perceptual-motor feedback loop. here, we presented new caledonian crows and humans with a novel horizontal string-pulling task. while the h ...	2012	23097511
new caledonian crows reason about hidden causal agents.	the ability to make inferences about hidden causal mechanisms underpins scientific and religious thought. it also facilitates the understanding of social interactions and the production of sophisticated tool-using behaviors. however, although animals can reason about the outcomes of accidental interventions, only humans have been shown to make inferences about hidden causal mechanisms. here, we show that tool-making new caledonian crows react differently to an observable event when it is caused ...	2012	22988112
population genetic structure and colonisation history of the tool-using new caledonian crow.	new caledonian crows exhibit considerable variation in tool making between populations. here, we present the first study of the species' genetic structure over its geographical distribution. we collected feathers from crows on mainland grande terre, the inshore island of toupéti, and the nearby island of maré where it is believed birds were introduced after european colonisation. we used nine microsatellite markers to establish the genotypes of 136 crows from these islands and classical populati ...	2012	22590576
new caledonian crows learn the functional properties of novel tool types.	new caledonian crows were presented with bird and emery's (2009a) aesop's fable paradigm, which requires stones to be dropped into a water-filled tube to bring floating food within reach. the crows did not spontaneously use stones as tools, but quickly learned to do so, and to choose objects and materials with functional properties. some crows discarded both inefficient and non-functional objects before observing their effects on the water level. interestingly, the crows did not learn to discrim ...	2011	22194779
the ecological significance of tool use in new caledonian crows.	tool use is so rare in the animal kingdom that its evolutionary origins cannot be traced with comparative analyses. valuable insights can be gained from investigating the ecological context and adaptive significance of tool use under contemporary conditions, but obtaining robust observational data is challenging. we assayed individual-level tool-use dependence in wild new caledonian crows by analyzing stable isotope profiles of the birds' feathers, blood, and putative food sources. bayesian diet ...	2010	20847272
an investigation into the cognition behind spontaneous string pulling in new caledonian crows.	the ability of some bird species to pull up meat hung on a string is a famous example of spontaneous animal problem solving. the "insight" hypothesis claims that this complex behaviour is based on cognitive abilities such as mental scenario building and imagination. an operant conditioning account, in contrast, would claim that this spontaneity is due to each action in string pulling being reinforced by the meat moving closer and remaining closer to the bird on the perch. we presented experience ...	2010	20179759
how do adult humans compare with new caledonian crows in tool selectivity?	we examined humans' tool selections on stick-and-tube tasks similar to those used to study crows' and other avian species' physical cognition. in experiment 1, the participants selected a stick from a set of 10 to retrieve a candy placed in a horizontal tube. although the stick that was selected depended on the distance to the candy, the participants generally did not select a stick whose length was the same as the candy's distance from the open end of the tube nor did they select the longest st ...	2010	20065352
diversification and cumulative evolution in new caledonian crow tool manufacture.	many animals use tools but only humans are generally considered to have the cognitive sophistication required for cumulative technological evolution. three important characteristics of cumulative technological evolution are: (i) the diversification of tool design; (ii) cumulative change; and (iii) high-fidelity social transmission. we present evidence that crows have diversified and cumulatively changed the design of their pandanus tools. in 2000 we carried out an intensive survey in new caledon ...	2003	12737666