Ruhr, Ilan M.; orcid: 0000-0001-9243-7055Rose, Kayleigh A. R.; orcid: 0000-0001-7023-2809Sellers, William I.; orcid: 0000-0002-2913-5406Crossley, Dane A., II; orcid: 0000-0001-9683-7013Codd, Jonathan R.; orcid: 0000-0003-0211-1786; email: jonathan.codd@manchester.ac.uk2021-06-012021-06-012021-03-032021-01-26Proceedings of the Royal Society B, volume 288, issue 1946, page 20210213http://hdl.handle.net/10034/624800From The Royal Society via Jisc Publications RouterHistory: received 2021-01-26, accepted 2021-01-28, pub-electronic 2021-03-03, pub-print 2021-03-10Article version: VoRPublication status: PublishedFunder: Leverhulme Trust; Id: http://dx.doi.org/10.13039/501100000275; Grant(s): RPG-2019-104Testudines are susceptible to inversion and self-righting 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 advantageous in overcoming the detriments of inversion.Licence for VoR version of this article: http://creativecommons.org/licenses/by/4.0/Morphology and biomechanicsResearch articlestestudinemorphologyneckallometryontogenybiomechanicsarticle2021-06-01