Whole animal measurements of shear and adhesive forces in adult tree frogs: insights into underlying mechanisms of adhesion obtained from studying the effects of size and scale

Barnes, W. J. P., Smith, J. M. and Oines, C. (2006) Whole animal measurements of shear and adhesive forces in adult tree frogs: insights into underlying mechanisms of adhesion obtained from studying the effects of size and scale. Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology, 192(11), pp. 1179-1191. (doi:10.1007/s00359-006-0146-1)

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Abstract

This allometric study of adhesion in 15 Trinidadian tree frog species investigates how relationships between length, area and mass limit the ability of adult frog species of different sizes to adhere to inclined and overhanging surfaces. Our experiments show that hylid frogs possess an area-based wet adhesive system in which larger species are lighter than expected from isometry and adhere better than expected from their toe pad area. However, in spite of these adaptations, larger species adhere less well than smaller species. In addition to these adhesive forces, tree frogs also generate significant shear forces that scale with mass, suggesting that they are frictional forces. Toe pads detach by peeling and frogs have strategies to prevent peeling from taking place while they are adhering to surfaces, including orienting themselves head-up on slopes. The scaling of tree frog adhesion is also used to distinguish between different models for adhesion, including classic formulae for capillarity and Stefan adhesion. These classic equations grossly overestimate the adhesive forces that tree frogs produce. More promising are peeling models, designed to predict the pull-off forces of adhesive tape. However, more work is required before we can qualitatively and quantitatively describe the adhesive mechanism of tree frogs.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Barnes, Dr W.Jon.P
Authors: Barnes, W. J. P., Smith, J. M., and Oines, C.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology
Publisher:Springer
ISSN:0340-7594
ISSN (Online):1432-1351
Published Online:19 August 2006

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