Cognitive psychology of tool use in New Caledonian crows (Corvus moneduloides ) Alexander Allan Scott Weir Magdalen College and Department of Zoology University of Oxford Thesis submitted for the Degree of Doctor of Philosophy Trinity Term 2005 Cognitive psychology of tool use in New Caledonian crows (Corvus moneduloides ) Alexander Allan Scott Weir, Magdalen College and Department of Zoology Thesis submitted for the Degree of Doctor of Philosophy, Trinity Term, 2005 ABSTRACT Most studies into the evolution of humans’ manufacture and use of tools have concentrated on non-human primates. Within the past decade, however, it has been reported that wild New Caledonian crows make and use tools as complex as those of chimpanzees, and that aspects of their behaviour may be culturally transmitted. In this thesis, I present work examining the cognitive basis of New Caledonian crows’ tool-oriented behaviour. I begin by reviewing the hotly-disputed issue of whether non-human animals are capable of ‘reasoning’ in the physical domain, and examining experiments designed to address this issue. It has often been claimed that naturally-occurring tool use and manufacture indicates special cognitive abilities, so I critically analyse this argument and propose a framework that might allow the question to be tested empirically. After reviewing what is known of the ecology of New Caledonian crows, I address cognition directly, presenting results from two studies into their understanding of hooks and tool shape. I report that one subject showed remarkable innovation and flexibility by spontaneously making hooks out of wire when she needed a hooked tool, and by quickly transferring this ability to novel material requiring a different technique. However, it was not clear if her behaviour reflected a full and true understanding of the task and tool properties. I also investigated whether the crows showed lateralised tool use, since wild crows have a population-wide bias for making tools using the left side of their bill. I found that individual captive crows almost always use tools with the same laterality, but there was no consistency across individuals (similar to observations in chimpanzees), suggesting that tool use and manufacture might have different neural underpinnings. Finally, a study on hand-raised crows found that they reliably developed tool use and basic tool manufacture without ever observing others using or making tools, suggesting that they have a genetic propensity to use tools to retrieve food. However, none of the juveniles ever made tools as sophisticated as ones made by wild crows, so the possibility remains that social learning is important in the natural acquisition of tool-oriented behaviour. i Acknowledgements There are so many people who have helped so much over the years it is hard to know where to begin! But first thanks must go to my supervisors, Alex Kacelnik and Jackie Chappell, who introduced me to the crows, provided constant encouragement and support, inspiring discussions and debates, and most importantly, friendship. Thanks also, Jackie, for so generously allowing me to use experimental apparatus you had designed and built, and for doing the hard work of capturing the first subjects and setting up the initial colony. I have been very lucky throughout my DPhil to have help and support from so many other members of the Behavioural Ecology Research Group. Ben Kenward joined the crow team just in time for all the hassles and difficulties of planning a field trip to New Caledonia to capture more crows; he made the whole process, and building new aviaries back in Oxford and hand-raising baby crows, much easier and more fun. Ben has also been great at being the sceptical voice in the group, leading to many enjoyable (and sometimes heated!) debates. Christian Rutz somehow managed to devote huge amounts of time to the crows despite being in the final stages of his own DPhil on goshawks, and he was instrumental in helping to write the grant application that has enabled us to continue with this work for the next three years. Thanks Chris also for always finding the time to provide statistical advice (not to mention teaching me how to recognise birds by their wing-beat frequency…!). Radha Nair kindly devoted many hours to teaching me how to extract and process crow brains, as well as preparing and fixing many herself – I’m sorry it has taken so long to do anything with them, but I promise we will! Jo Wimpenny, Lucas Bluff, Stephen Barlow, and more recently Irmgard Teschke and Stuti Mehta, made an enormous difference to my workload in the last year by being willing to do more than their fair share of bird husbandry and aviary building – I very much doubt this thesis would be complete by now if they had not. As always when doing fieldwork in a different country, many people in New Caledonia were instrumental in enabling us to capture and bring back crows. Particular thanks must go to Christophe Lambert and Annie-Claude Panché of the Service des Parcs et Reserves Terrestres, who gave us permission to work there, took care of captured crows in the Parc Forestier, arranged for their shipment to the UK, and were helpful in so many other ways. Tino and Danni Lecren also introduced us to the crazier side of New Caledonia, as well as seeming to know everyone and insisting on giving up their days to take us to the best crow sites, even when we thought we knew better. Thanks too to Gavin Hunt, who has taught us almost everything we know about the crows in the wild. Many technical and administrative staff in the Department of Zoology have provided support and help, especially David Wilson who has been very diligent in looking after the crows’ everyday husbandry, Judith Lloyd and Jason Hogg who arranged logistics and building work, and Dave Palmer and Tony Price who catered for our sometimes obscure carpentry and metalwork requirements. My interest in science and some of the ideas presented in this thesis have been inspired by conversations with many people over the years. Especially important were my ii undergraduate biology tutors, particularly David Roberts, Graham Stone, and David Raubenheimer, who are largely responsible for my decision to stay in science and do a DPhil. The supervisors of my Masters projects, Anna Nobre, Heather Jordan, and Kim Plunkett, also helped me develop my interests and scientific thinking, and the regular exchange of ideas with the Cambridge corvid research group has been very stimulating. My family and friends have been an enormous source of fun, support, and sanity. My parents, grandparents, and brother have always encouraged me and shown interest in my work, even though it must have seemed like an obscure and strange thing to want to do. My grandfather in particular had a passion for birds, and had had a pet jackdaw when he was a boy – perhaps my interest in corvids is inherited! My friends have constantly encouraged me when the thesis seemed like an insurmountable obstacle – thank you Jenny for all the delicious meals and chocolate cake (!) and Fe for the fun conversations accompanying them, Rich, Lucy, Hattie, and the rest of the zoology crew for guaranteeing that work finished early on Fridays, and all our friends from undergrad days for making sure that I remembered there was a welcoming world outside academia! Finally, the person who has kept me going all these years with her support, inspiration, friendship, and love. Thank you, Charlie, for always being willing to discuss experiments and problems, read my papers and thesis drafts and make fantastic suggestions; for encouraging me when I was demoralised, and for putting up with me when I had to spend all hours in the aviaries rearing baby crows and writing my thesis – I couldn’t have done it without you. As I said all those years ago: saya cinta padamu . My DPhil was funded as part of the Wellcome Trust’s 4-year Doctoral Programme in Neuroscience, and I was also very grateful to receive an award from the Oxford University Vice-Chancellors’ Fund, a Senior MacKinnon Scholarship from Magdalen College, and the very generous prize from the Royal Institution and L’Oreal, all of which helped me get through the final months after my Wellcome Trust funding ended. iii Author’s contribution Regarding Alex Weir’s thesis submitted for the degree of DPhil, Trinity Term 2005, entitled “Cognitive psychology of tool use in New Caledonian crows ( Corvus moneduloides )” Chapter 1. Entirely my own work, apart from small parts of Section 1.3 which were adapted from two publications that I co-authored (Kenward, Rutz, Weir, Chappell, & Kacelnik (2004), Ibis 146: 652-660; and Kacelnik, Chappell, Weir, & Kenward (in press), chapter in Comparative Cognition: Experimental Explorations of Animal Intelligence , eds. Wasserman & Zentall). Chapter 2. Entirely my own work. Chapter 3. Entirely my own work, apart from some sentences in the section describing Experiment 2, which were taken from a paper I wrote with two colleagues (Weir, Chappell, & Kacelnik (2002) Science 297: 981 – see Appendix 5). The apparatus used in the experiments was designed and built by Jackie Chappell. Chapter 4. Entirely my own work. Chapter 5. I designed the experiment with input from the other co-authors. I collected and analysed the data and wrote the first draft of the paper. The co-authors were involved in editing and revising the paper. Chapters 6. The crows were hand-raised by Ben Kenward and myself (with occasional help from other group members). The experiment was designed by all authors in collaboration. Ben Kenward conducted the demonstrations and collected detailed behavioural data (reported in Appendix 6); I helped with some of the video recording of sessions.