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Small vertebrates running on uneven terrain : a biomechanical study of two differently specialised lacertid lizards

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Abstract
While running, small animals frequently encounter large terrain variations relative to their body size, therefore, terrain variations impose important functional demands on small animals. Nonetheless, we have previously observed in lizards that running specialists can maintain a surprisingly good running performance on very uneven terrains. The relatively large terrain variations are ofset by their capacity for leg adjustability that ensures a ‘smooth ride’ of the centre of mass (CoM). The question as to how the efect of an uneven terrain on running performance and locomotor costs difers between species exhibiting diverse body build and locomotor specializations remains. We hypothesise that specialized runners with long hind limbs can cross uneven terrain more efciently than specialized climbers with a dorso-ventrally fattened body and equally short fore and hind limbs. This study reports 3D kinematics using high-speed videos (325Hz) to investigate leg adjustability and CoM movements in two lacertid lizards (Acanthodactylus boskianus, running specialist; Podarcis muralis, climbing specialist). We investigated these parameters while the animals were running on a level surface and over a custommade uneven terrain. We analysed the CoM dynamics, we evaluated the fuctuations of the positive and negative mechanical energy, and we estimated the overall cost of transport. Firstly, the results reveal that the climbers ran at lower speeds on fat level terrain but had the same cost of transport as the runners. Secondly, contrary to the running specialists, the speed was lower and the energy expenditure higher in the climbing specialists while running on uneven terrain. While leg movements adjust to the substrates’ variations and enhance the stability of the CoM in the running specialist, this is not the case in the climbing specialist. Although their legs are kept more extended, the amplitude of movement does not change, resulting in an increase of the movement of the CoM and a decrease in locomotor efciency. These results are discussed in light of the respective (micro-)habitat of these species and suggest that energy economy can also be an important factor for small vertebrates.
Keywords
running, small vertebrates, biomechanical study

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MLA
Druelle, François, et al. “Small Vertebrates Running on Uneven Terrain : A Biomechanical Study of Two Differently Specialised Lacertid Lizards.” SCIENTIFIC REPORTS, vol. 9, no. 1, 2019.
APA
Druelle, F., Goyens, J., Vasilopoulou-Kampitsi, M., & Aerts, P. (2019). Small vertebrates running on uneven terrain : a biomechanical study of two differently specialised lacertid lizards. SCIENTIFIC REPORTS, 9(1).
Chicago author-date
Druelle, François, Jana Goyens, Menelia Vasilopoulou-Kampitsi, and Peter Aerts. 2019. “Small Vertebrates Running on Uneven Terrain : A Biomechanical Study of Two Differently Specialised Lacertid Lizards.” SCIENTIFIC REPORTS 9 (1).
Chicago author-date (all authors)
Druelle, François, Jana Goyens, Menelia Vasilopoulou-Kampitsi, and Peter Aerts. 2019. “Small Vertebrates Running on Uneven Terrain : A Biomechanical Study of Two Differently Specialised Lacertid Lizards.” SCIENTIFIC REPORTS 9 (1).
Vancouver
1.
Druelle F, Goyens J, Vasilopoulou-Kampitsi M, Aerts P. Small vertebrates running on uneven terrain : a biomechanical study of two differently specialised lacertid lizards. SCIENTIFIC REPORTS. 2019;9(1).
IEEE
[1]
F. Druelle, J. Goyens, M. Vasilopoulou-Kampitsi, and P. Aerts, “Small vertebrates running on uneven terrain : a biomechanical study of two differently specialised lacertid lizards,” SCIENTIFIC REPORTS, vol. 9, no. 1, 2019.
@article{8649632,
  abstract     = {While running, small animals frequently encounter large terrain variations relative to their body size,
therefore, terrain variations impose important functional demands on small animals. Nonetheless, we
have previously observed in lizards that running specialists can maintain a surprisingly good running
performance on very uneven terrains. The relatively large terrain variations are ofset by their capacity
for leg adjustability that ensures a ‘smooth ride’ of the centre of mass (CoM). The question as to how
the efect of an uneven terrain on running performance and locomotor costs difers between species
exhibiting diverse body build and locomotor specializations remains. We hypothesise that specialized
runners with long hind limbs can cross uneven terrain more efciently than specialized climbers with a
dorso-ventrally fattened body and equally short fore and hind limbs. This study reports 3D kinematics
using high-speed videos (325Hz) to investigate leg adjustability and CoM movements in two lacertid
lizards (Acanthodactylus boskianus, running specialist; Podarcis muralis, climbing specialist). We
investigated these parameters while the animals were running on a level surface and over a custommade uneven terrain. We analysed the CoM dynamics, we evaluated the fuctuations of the positive and
negative mechanical energy, and we estimated the overall cost of transport. Firstly, the results reveal
that the climbers ran at lower speeds on fat level terrain but had the same cost of transport as the
runners. Secondly, contrary to the running specialists, the speed was lower and the energy expenditure
higher in the climbing specialists while running on uneven terrain. While leg movements adjust to the
substrates’ variations and enhance the stability of the CoM in the running specialist, this is not the case
in the climbing specialist. Although their legs are kept more extended, the amplitude of movement does
not change, resulting in an increase of the movement of the CoM and a decrease in locomotor efciency.
These results are discussed in light of the respective (micro-)habitat of these species and suggest that
energy economy can also be an important factor for small vertebrates.},
  articleno    = {16858},
  author       = {Druelle, François and Goyens, Jana and Vasilopoulou-Kampitsi, Menelia and Aerts, Peter},
  issn         = {2045-2322},
  journal      = {SCIENTIFIC REPORTS},
  keywords     = {running,small vertebrates,biomechanical study},
  language     = {eng},
  number       = {1},
  pages        = {11},
  title        = {Small vertebrates running on uneven terrain : a biomechanical study of two differently specialised lacertid lizards},
  url          = {http://dx.doi.org/10.1038/s41598-019-53329-5},
  volume       = {9},
  year         = {2019},
}

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