The influence of claw morphology on gripping efficiency

Turnbull, Graham; Chari, Sutejas; Li, Zehao; Yang, Ziyue; Alam, Catharina Maria; Clemente, Christofer J.; Alam, Parvez

Abstract

This paper considers the effects of claw morphology on the gripping efficiency of arboreal (Varanus varius) and burrowing (Varanus gouldii and Varanus panoptes) lizards. To ensure a purely morphological comparison between the lizards, we circumvent the material effects of claws from different species, by modelling and testing claw replicates of the same material properties. We correlate climbing efficiency to critical morphological features including; claw height (hc), width (wc), length (lc), curvature () and tip angle (γ), which are expressed as ratios to normalise mechanically beneficial claw structures. We find that there is strong correlation between the static grip force Fsg and the claw aspect and the cross-sectional rigidity ratio , and milder correlation (i.e. higher scatter) with the profile rigidity ratio . These correlations are also true for the interlocking grip force Fint over different shaped and sized protuberances, though we note that certain protuberance size-shape couplings are of detriment to the repeatability of Fint. Of the three lizard species, the claws of the arboreal (V. varius) are found to be superior to those of the burrower lizards (V. gouldii and V. panoptes) as a result of the V. varius claws having a smaller aspect, a higher cross-sectional rigidity ratio and a small profile rigidity ratio, which are deemed noteworthy morphological parameters that influence a claw's ability to grip effectively.

Citation

Turnbull, G., Chari, S., Li, Z., Yang, Z., Alam, C. M., Clemente, C. J., & Alam, P. (2023). The influence of claw morphology on gripping efficiency. Biology Open, 12(5), Article bio059874. https://doi.org/10.1242/bio.059874

• Journal Article Type: Article
• Acceptance Date: Apr 12, 2023
• Online Publication Date: May 16, 2023
• Publication Date: 2023-05
• Deposit Date: May 22, 2023
• Publicly Available Date: May 22, 2023
• Journal: Biology Open
• Publisher: Company of Biologists
• Peer Reviewed: Peer Reviewed
• Volume: 12
• Issue: 5
• Article Number: bio059874
• DOI: https://doi.org/10.1242/bio.059874
• Keywords: Lizard claw, Morphology, Climbing