Hill, I. D.C., Dong, B., Barnes, W. J. P., Ji, A. and Endlein, T. (2018) The biomechanics of tree frogs climbing curved surfaces: a gripping problem. Journal of Experimental Biology, 221(5), jeb168179. (doi: 10.1242/jeb.168179) (PMID:29361584)
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Abstract
The adhesive mechanisms of climbing animals have become an important research topic because of their biomimetic implications. We examined the climbing abilities of hylid tree frogs on vertical cylinders of differing diameter and surface roughness to investigate the relative roles of adduction forces (gripping) and adhesion. Tree frogs adhere using their toe pads and subarticular tubercles, the adhesive joint being fluid-filled. Our hypothesis was that, on an effectively flat surface (adduction forces on the largest 120 mm diameter cylinder were insufficient to allow climbing), adhesion would effectively be the only means by which tree frogs could climb, but on the two smaller diameter cylinders (44 mm and 13 mm), frogs could additionally utilise adduction forces by gripping the cylinder either with their limbs outstretched or by grasping around the cylinder with their digits, respectively. The frogs' performance would also depend on whether the surfaces were smooth (easy to adhere to) or rough (relatively non-adhesive). Our findings showed that climbing performance was highest on the narrowest smooth cylinder. Frogs climbed faster, frequently using a 'walking trot' gait rather than the 'lateral sequence walk' used on other cylinders. Using an optical technique to visualize substrate contact during climbing on smooth surfaces, we also observed an increasing engagement of the subarticular tubercles on the narrower cylinders. Finally, on the rough substrate, frogs were unable to climb the largest diameter cylinder, but were able to climb the narrowest one slowly. These results support our hypotheses and have relevance for the design of climbing robots.
| Item Type: | Articles |
|---|---|
| Keywords: | Adhesion, climbing, Tree frog. |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Hill, Mr Iain and Barnes, Dr William |
| Authors: | Hill, I. D.C., Dong, B., Barnes, W. J. P., Ji, A., and Endlein, T. |
| College/School: | College of Medical Veterinary and Life Sciences > School of Molecular Biosciences College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine |
| Journal Name: | Journal of Experimental Biology |
| Publisher: | Company of Biologists |
| ISSN: | 0022-0949 |
| ISSN (Online): | 1477-9145 |
| Published Online: | 19 January 2018 |
| Copyright Holders: | Copyright © 2018 The Company of Biologists Ltd. |
| First Published: | First published in Journal of Experimental Biology 221(5): jeb168179 |
| Publisher Policy: | Reproduced in accordance with the copyright policy of the publisher |
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