The ostrich (Struthio camelus) is widely appreciated as a fast and agile bipedal athlete, and is a useful comparative bipedal model for human locomotion. Here, we used GPS-IMU sensors to measure naturally selected gait dynamics of ostriches roaming freely over a wide range of speeds in an open field and developed a quantitative method for distinguishing walking and running using accelerometry. We compared freely selected gait–speed distributions with previous laboratory measures of gait dynamics and energetics. We also measured the walk–run and run–walk transition speeds and compared them with those reported for humans. We found that ostriches prefer to walk remarkably slowly, with a narrow walking speed distribution consistent with minimizing cost of transport (CoT) according to a rigid-legged walking model. The dimensionless speeds of the walk–run and run–walk transitions are slower than those observed in humans. Unlike humans, ostriches transition to a run well below the mechanical limit necessitating an aerial phase, as predicted by a compass-gait walking model. When running, ostriches use a broad speed distribution, consistent with previous observations that ostriches are relatively economical runners and have a flat curve for CoT against speed. In contrast, horses exhibit U-shaped curves for CoT against speed, with a narrow speed range within each gait for minimizing CoT. Overall, the gait dynamics of ostriches moving freely over natural terrain are consistent with previous lab-based measures of locomotion. Nonetheless, ostriches, like humans, exhibit a gait-transition hysteresis that is not explained by steady-state locomotor dynamics and energetics. Further study is required to understand the dynamics of gait transitions.
The authors declare no competing or financial interests.
M.A.D. and A.J.C. conceived and designed the study, A.J.C. and G.S.N. performed the experiments, G.S.N., J.H. and M.A.D. analysed the data, J.H. and M.A.D. wrote the paper, and M.A.D. supervised the research.
This work was supported grant (BB/H005838/1) to M.A.D. from the Biotechnology and Biological Sciences Research Council (BBSRC).
Data are available from the Dryad Digital Repository: http://dx.doi.org/10.5061/dryad.h846r.
Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.142588.supplemental
- Received April 28, 2016.
- Accepted August 8, 2016.
- © 2016. Published by The Company of Biologists Ltd