Examining the accuracy of trackways for predicting gait selection and speed of locomotion

Abstract

Background: Using Froude numbers (Fr) and relative stride length (stride length: hip height), trackways have been widely used to determine the speed and gait of an animal. This approach, however, is limited by the ability to estimate hip height accurately and by the lack of information related to the substrate properties when the tracks were made, in particular for extinct fauna. By studying the Svalbard ptarmigan moving on snow, we assessed the accuracy of trackway predictions from a species-specific model and two additional Fr based models by ground truthing data extracted from videos as the tracks were being made. Results: The species-specific model accounted for more than 60% of the variability in speed for walking and aerial running, but only accounted for 19% when grounded running, likely due to its stabilizing role while moving faster over a changing substrate. The error in speed estimated was 0-35% for all gaits when using the species-specific model, whereas Fr based estimates produced errors up to 55%. The highest errors were associated with the walking gait. The transition between pendular to bouncing gaits fell close to the estimates using relative stride length described for other extant vertebrates. Conversely, the transition from grounded to aerial running appears to be species specific and highly dependent on posture and substrate. Conclusion: Altogether, this study highlights that using trackways to derive predictions on the locomotor speed and gait, using stride length as the only predictor, are problematic as accurate predictions require information from the animal in question.

Natural Frequency Method: estimating the preferred walking speed of Tyrannosaurus rex based on tail natural frequency

“…Recent amendments have been proposed to improve DS-based estimations, either by focusing on swing phase dynamics [52], or by incorporating taxon-specific morphological parameters to reduce uncertainty [53]. The latter are of course difficult to obtain from a fossilized trackway.…”

“…The resulting step lengths differed by less than 4% from the suggested preferred relative stride length. Whenever considering trackway data, substrate-related uncertainties will prevent any straightforward interpretation [53,54], although presumably, these would not affect tail natural frequency.…”

The Influence of Snow Properties on Speed and Gait Choice in the Svalbard Rock Ptarmigan (Lagopus muta hyperborea)

“… \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${l_{{\rm{stride}}}}$\end{document} was measured using ImageJ v. 1.52q ( Schneider et al 2012 ). Grounded running \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$U$\end{document} was not predicted because of the high error associated with the predictions based on \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${l_{{\rm{stride}}}}$\end{document} and the lack of certainty of gait identification ( Marmol-Guijarro et al 2020 ).…”

Dots on a screen: The past, present, and future of morphometrics in the study of nonavian dinosaurs

“…More recently, evolutionary robotics and biomechanical modeling approaches have been employed with body fossils to assess both gait and running speed (Bates et al, 2012; Hutchinson, 2004; Sellers & Manning, 2007). Such methods complement direct evidence from trackways, which may be problematic in predicting locomotor speed and gait when used singularly (Marmol‐Guijarro et al, 2020), granting paleobiologists an unprecedented view into nonavian dinosaur locomotor behavior.…”