Adaptive bill morphology for enhanced tool manipulation in New Caledonian crows

Early increased sophistication of human tools is thought to be underpinned by adaptive morphology for efficient tool manipulation. Such adaptive specialisation is unknown in nonhuman primates but may have evolved in the New Caledonian crow, which has sophisticated tool manufacture. The straightness...

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Bibliographic Details
Published in:Scientific reports 2016-03, Vol.6 (1), p.22776-22776, Article 22776
Main Authors: Matsui, Hiroshi, Hunt, Gavin R., Oberhofer, Katja, Ogihara, Naomichi, McGowan, Kevin J., Mithraratne, Kumar, Yamasaki, Takeshi, Gray, Russell D., Izawa, Ei-Ichi
Format: Article
Language:English
Subjects:
631/158/857
631/601/1332
Animals
Beak - anatomy & histology
Behavior, Animal
Biological Evolution
Computed tomography
Crows - anatomy & histology
Crows - physiology
Humanities and Social Sciences
Mandible
Morphology
multidisciplinary
Principal Component Analysis
Principal components analysis
Science
Tomography, X-Ray Computed
Tool use
Tool Use Behavior
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Summary:Early increased sophistication of human tools is thought to be underpinned by adaptive morphology for efficient tool manipulation. Such adaptive specialisation is unknown in nonhuman primates but may have evolved in the New Caledonian crow, which has sophisticated tool manufacture. The straightness of its bill, for example, may be adaptive for enhanced visually-directed use of tools. Here, we examine in detail the shape and internal structure of the New Caledonian crow’s bill using Principal Components Analysis and Computed Tomography within a comparative framework. We found that the bill has a combination of interrelated shape and structural features unique within Corvus and possibly birds generally. The upper mandible is relatively deep and short with a straight cutting edge and the lower mandible is strengthened and upturned. These novel combined attributes would be functional for (i) counteracting the unique loading patterns acting on the bill when manipulating tools, (ii) a strong precision grip to hold tools securely and (iii) enhanced visually-guided tool use. Our findings indicate that the New Caledonian crow’s innovative bill has been adapted for tool manipulation to at least some degree. Early increased sophistication of tools may require the co-evolution of morphology that provides improved manipulatory skills.
ISSN:2045-2322
2045-2322
DOI:10.1038/srep22776