The social cognitive abilities of the Clark’s nutcracker: from self to other
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Date
2016
Authors
Clary, Dawson
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Abstract
This dissertation explored the social cognitive abilities of the Clark’s nutcracker (Nucifraga columbiana), a relatively non-social, food-caching corvid. Corvids are a family of large-brained birds, which are capable of remarkable cognitive feats (e.g., future planning, tool use). These cognitive abilities have been revealed predominantly by testing social species, supporting popular theories that living in social groups drove the evolution of complex cognition. However, few studies have investigated the social cognitive abilities of corvid species that do not live in large groups. Here, I developed novel procedures using the food-caching behaviour of Clark’s nutcrackers as a tool to explore two cognitive abilities predicted to be limited to social species: mirror self-recognition (Chapter 2) and cooperation (Chapter 4). In Chapter 2, birds cached food when alone, with a conspecific present, and with a regular or blurry mirror. The nutcrackers suppressed caching with a regular mirror (as done with a conspecific), but not with the blurry mirror. When integrated with the traditional ‘mark test’, the birds also showed evidence of self-recognition with the blurry mirror by attempting to remove a coloured mark placed on their body with the blurry mirror, but not with an opaque barrier. In Chapter 3, I discuss the importance of self-recognition as a precursor for complex and flexible social cognitive abilities such as cooperation. To investigate cooperation, in Chapter 4 the birds experienced having their caches exchanged with another bird over multiple trials. This procedure assessed whether the normal response of cache suppression with a conspecific could be over-ridden if the experimental contingencies made cache sharing beneficial. The nutcrackers continued to cache in this context, and male birds increased caching when cooperation from the conspecific was exaggerated artificially by the experimenter. Combined, the results indicate the non- social Clark’s nutcracker is capable of mirror self-recognition, and the ability to distinguish one’s ‘self’ from others may facilitate flexible caching decisions, contrary to the predictions of the social living hypotheses. The findings indicate social living alone does not strongly predict complex cognitive abilities and, instead, that multiple evolutionary paths exist for the development of complex cognition.
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Keywords
Corvid, Comparative cognition, Clark's nutcracker, Cooperation, Cache protection, Mirror self-recognition, Complex cognition, Social living hypothesis, Evolution