The scaling of ground reaction forces and duty factor in monitor lizards: implications for locomotion in sprawling tetrapods

Robert L Cieri; Taylor J M Dick; Robert Irwin; Daniel Rumsey; Christofer J Clemente

doi:10.1098/rsbl.2020.0612

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The scaling of ground reaction forces and duty factor in monitor lizards: implications for locomotion in sprawling tetrapods

Journal article

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The scaling of ground reaction forces and duty factor in monitor lizards: implications for locomotion in sprawling tetrapods

Robert L Cieri, Taylor J M Dick, Robert Irwin, Daniel Rumsey and Christofer J Clemente

Biology Letters, Vol.17(2), pp.1-8

2021

DOI: https://doi.org/10.1098/rsbl.2020.0612

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Abstract

effective mechanical advantage

impulse

kinetics

speed

varanids

Geometric scaling predicts a major challenge for legged, terrestrial locomotion. Locomotor support requirements scale identically with body mass ( α M 1 ), while force-generation capacity should scale α M 2/3 as it depends on muscle cross-sectional area. Mammals compensate with more upright limb postures at larger sizes, but it remains unknown how sprawling tetrapods deal with this challenge. Varanid lizards are an ideal group to address this question because they cover an enormous body size range while maintaining a similar bent-limb posture and body proportions. This study reports the scaling of ground reaction forces and duty factor for varanid lizards ranging from 7 g to 37 kg. Impulses (force×time) ( α M 0.99−1.34 ) and peak forces ( α M 0.73−1.00 ) scaled higher than expected. Duty factor scaled α M 0.04 and was higher for the hindlimb than the forelimb. The proportion of vertical impulse to total impulse increased with body size, and impulses decreased while peak forces increased with speed.

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Title: The scaling of ground reaction forces and duty factor in monitor lizards: implications for locomotion in sprawling tetrapods
Authors: Robert L Cieri (Author) - University of the Sunshine Coast, Queensland, School of Science and Engineering - Legacy
Taylor J M Dick (Author) - The University of Queensland
Robert Irwin (Author) - Australia Zoo
Daniel Rumsey (Author) - Australian Reptile Park
Christofer J Clemente (Author) - University of the Sunshine Coast, Queensland, School of Science and Engineering - Legacy
Publication details: Biology Letters, Vol.17(2), pp.1-8
Publisher: The Royal Society Publishing
Date published: 2021
DOI: 10.1098/rsbl.2020.0612
ISSN: 1744-957X; 1744-9561
Grants: Understanding evolution through the use of optimization of biologically mimicking robotic systems., DP180100220, Australian Research Council (Australia, Canberra) - ARC
Design of a biologically inspired running and climbing robotic lizard, DE120101503, Australian Research Council (Australia, Canberra) - ARC
Grant note: National Science Foundation (1256065) and the Natural Sciences and Engineering Research Council of Canada.
Organisation Unit: School of Science and Engineering - Legacy; School of Science, Technology and Engineering
Language: English
Record Identifier: 99508608702621
Output Type: Journal article

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