Abstract
Humans and birds use very different running styles. Unlike humans, birds adopt "grounded running"at intermediate speeds-a running gait where at least one foot always maintains ground contact. Avian grounded running is a paradox: Animals usually minimize locomotor energy expenditure, but birds prefer grounded running despite incurring higher energy costs. Using predictive gait simulations of the emu (Dromaius novaehollandiae), we resolve this paradox by demonstrating that grounded running represents an optimal gait for birds, from both energetics and muscle excitations perspectives. Our virtual experiments decoupled effects of posture and tendon elasticity, biomechanically relevant anatomical features that cannot be isolated in real birds. The avian body plan prevents (near) vertical leg postures, making the running style used by humans impossible. Under this anatomical constraint, grounded running is optimal if the muscles produce the highest forces in crouched postures, as is true in most birds. Shared anatomical features suggest that, as a behavior, avian grounded running first evolved within non-avian dinosaurs.
| Original language | English |
|---|---|
| Article number | eado0936 |
| Pages (from-to) | 1-19 |
| Number of pages | 19 |
| Journal | Science advances |
| Volume | 10 |
| Issue number | 39 |
| Early online date | 25 Sept 2024 |
| DOIs | |
| Publication status | Published - Sept 2024 |
Bibliographical note
Publisher Copyright:© 2024 The Authors.
Funding
Acknowledgments: We thank R. Main, J. Goetz, J. Hutchinson, and L. Lamas for sharing emu data and assistance during data processing. We thank M. Daley, S. Gatesy, P. Bishop, A. Abourachid, and A. Koenders for helpful advice and discussions on avian locomotion. The authors are very appreciative of discussions with N. Bianco, R. Miller, A. Fox, A. van den Bogert, B. Umberger, and A. Falisse on the Moco forums, which were instrumental in shaping the simulation methodology implemented here. We also thank D. Polet, J. Usherwood, T. Geijtenbeek, W. Sellers, A. Koelewijn, K. Lemaire, F. Muijres, and J. van Leeuwen for discussions on gait simulations and mechanics in general. J. IJzer, L. van den Boom, and L. Walen are thanked for providing specimen access. V. van Bijlert provided helpful suggestions regarding Latin myological terminology. We thank V. Duurland for providing permission to photograph his emus, T. Brown for providing access to equipment, and M. Spithoven and M. Dempsey for assistance during data collection. Last, we are grateful to two anonymous reviewers, whose suggestions and feedback improved this manuscript. Funding: This work was supported by a European Association of Vertebrate Palaeontologists Research Grant (to P.v.B.). Author contributions: Conceptualization: P.v.B., K.v.S., A.S., and K.B. Simulations and programming: P.v.B. Visualizations: P.v.B. Data interpretation: P.v.B., K.v.S., A.S., and K.B. Writing: P.v.B., K.v.S., A.S., and K.B. Competing interests: The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Models, 3D meshes of the skeleton, raw simulator outputs, and predictive simulation code examples are available on our SimTK project page: https://simtk.org/projects/emily_project (which stands for Emu Model for Investigating Locomotor dYnamics).
| Funders | Funder number |
|---|---|
| European Association of Vertebrate Palaeontologists Research | |
| European Association of Vertebrate Palaeontologists Research |