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      The running kinematics of free-roaming giraffes, measured using a low cost unmanned aerial vehicle (UAV)

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          Abstract

          The study of animal locomotion can be logistically challenging, especially in the case of large or unhandleable animals in uncontrolled environments. Here we demonstrate the utility of a low cost unmanned aerial vehicle (UAV) in measuring two-dimensional running kinematics from free-roaming giraffes ( Giraffa camelopardalis giraffa) in the Free State Province, South Africa. We collected 120 Hz video of running giraffes, and calibrated each video frame using metatarsal length as a constant object of scale. We tested a number of methods to measure metatarsal length. The method with the least variation used close range photography and a trigonometric equation to spatially calibrate the still image, and derive metatarsal length. In the absence of this option, a spatially calibrated surface model of the study terrain was used to estimate topographical dimensions in video footage of interest. Data for the terrain models were collected using the same equipment, during the same study period. We subsequently validated the accuracy of the UAV method by comparing similar speed measurements of a human subject running on a treadmill, with treadmill speed. At 8 m focal distance we observed an error of 8% between the two measures of speed. This error was greater at a shorter focal distance, and when the subject was not in the central field of view. We recommend that future users maximise the camera focal distance, and keep the subject in the central field of view. The studied giraffes used a grounded rotary gallop with a speed range of 3.4–6.9 ms −1 (never cantering, trotting or pacing), and lower duty factors when compared with other cursorial quadrupeds. As this pattern might result in adverse increases in peak vertical limb forces with speed, it was notable to find that contralateral limbs became more in-phase with speed. Considering the latter pattern and the modest maximal speed of giraffes, we speculate that tissue safety factors are maintained within tolerable bounds this way. Furthermore, the angular kinematics of the neck were frequently isolated from the pitching of the body during running; this may be a result of the large mass of the head and neck. Further field experiments and biomechanical models are needed to robustly test these speculations.

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          Most cited references 29

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          Software techniques for two- and three-dimensional kinematic measurements of biological and biomimetic systems.

           Tyson Hedrick (2008)
          Researchers studying aspects of locomotion or movement in biological and biomimetic systems commonly use video or stereo video recordings to quantify the behaviour of the system in question, often with an emphasis on measures of position, velocity and acceleration. However, despite the apparent simplicity of video analysis, it can require substantial investment of time and effort, even when performed with adequate software tools. This paper reviews the underlying principles of video and stereo video analysis as well as its automation and is accompanied by fully functional and freely available software implementation.
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            A dynamic similarity hypothesis for the gaits of quadrupedal mammals

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              The Gaits of Bipedal and Quadrupedal Animals

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                Author and article information

                Contributors
                Journal
                PeerJ
                PeerJ
                peerj
                peerj
                PeerJ
                PeerJ Inc. (San Diego, USA )
                2167-8359
                12 February 2019
                2019
                : 7
                Affiliations
                [1 ]Structure & Motion Laboratory, Royal Veterinary College , Hatfield, United Kingdom
                [2 ]Faculty of Natural and Agricultural Sciences, Department of Animal, Wildlife and Grassland Sciences, University of the Free State , Bloemfontein, South Africa
                Article
                6312
                10.7717/peerj.6312
                6376938
                ©2019 Basu et al.

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ) and either DOI or URL of the article must be cited.

                Funding
                Funded by: NERC
                Award ID: NE/K004751/1
                Funded by: ERC
                Award ID: AD-G 323041
                Funded by: National Research Foundation
                Award ID: V106005
                Funded by: Society for Experimental Biology
                Funded by: Company of Biologists Travelling Fellowship
                This work was funded by NERC (PhD studentship for Christopher Basu; grant no. NE/K004751/1 to John Hutchinson), ERC (Advanced grant AD-G 323041 to Alan Wilson), National Research Foundation (South African project no. V106005 to Francois Deacon), Society for Experimental Biology student travel grant (Christopher Basu), and a Company of Biologists Travelling Fellowship (Christopher Basu). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Categories
                Biophysics
                Zoology
                Kinesiology

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