Turning turtle: Scaling relationships and self-righting ability in Chelydra serpentina

Testudines are susceptible to inversion and self-right using their necks, limbs, or both, to generate enough mechanical force to flip over. We investigated how shell morphology, neck length, and self-righting biomechanics scale with body mass during ontogeny in Chelydra serpentina, which uses neck-powered self-righting. We found that younger turtles flipped over twice as fast as older individuals. A simple geometric model predicted the relationships of shell shape and self-righting time with body mass. Conversely, neck force, power output, and kinetic energy increase with body mass at rates greater than predicted. These findings were correlated with relatively longer necks in younger turtles than would be predicted by geometric similarity. Therefore, younger turtles self-right with lower biomechanical costs than predicted by simple scaling theory. Considering younger turtles are more prone to inverting and their shells offer less protection, faster and less costly self-righting would be...

龟鳖目（Testudines）易发生翻倒，可通过颈部、四肢或二者协同产生足够机械力以完成自扶正动作。本研究以依赖颈部动力实现自扶正的北美拟鳄龟（Chelydra serpentina）为研究对象，探究了其个体发育过程中，壳体形态、颈部长度以及自扶正生物力学特性随体质量的异速缩放规律。研究结果显示，幼体龟的翻身速度为成体龟的两倍。通过简单几何模型，可预测壳体形态、自扶正时长与体质量间的关联关系。与之相反，颈部肌力、功率输出及动能随体质量的增长速率高于模型预测值。上述发现与幼体龟颈部长度较几何相似性理论预测值更长的现象存在相关性。因此，幼体龟完成自扶正动作的生物力学成本低于简单缩放理论的预测结果。考虑到幼体龟更易发生翻倒，且其壳体防护能力较弱，更快且成本更低的自扶正行为将有助于...