DOI: 10.5061/dryad.7h44j0zw8
title: Data from: Scaling and relations of morphology with locomotor kinematics in the sidewinder rattlesnake Crotalus cerastes

description: The movement of limbless terrestrial animals differs fundamentally from
 that of limbed animals, yet few scaling studies of their locomotor
 kinematics and morphology are available. We examined scaling and relations
 of morphology and locomotion in sidewinder rattlesnakes (Crotalus
 cerastes). During sidewinding locomotion, a snake lifts sections of its
 body up and forward while other sections maintain static ground contact.
 We used high-speed video to quantify whole-animal speed and acceleration;
 the height to which body sections are lifted; and the frequency,
 wavelength, amplitude, and skew angle (degree of tilting) of the body
 wave. Kinematic variables were not sexually dimorphic, and most did not
 deviate from isometry, except wave amplitude. Larger sidewinders were not
 faster, contrary to many results from limbed terrestrial animals. Free
 from the need to maintain dynamic similarity (because their locomotion is
 dominated by friction rather than inertia), limbless species may have
 greater freedom to modulate speed independently of body size. Path
 analysis supported: (1) a hypothesized relationship between body width and
 wavelength, indicating that stouter sidewinders form looser curves; (2) a
 strong relationship between cycle frequency and whole-animal speed; and
 (3) weaker effects of wavelength (positive) and amplitude (negative) on
 speed. We suggest that sidewinding snakes may face a limit on stride
 length (to which amplitude and wavelength both contribute), beyond which
 they sacrifice stability. Thus, increasing frequency may be the best way
 to increase speed. Finally, frequency and skew angle were correlated, a
 result that deserves future study from the standpoint of both kinematics
 and physiology.
description: Full details on data collection and processing can be found in
 the Methods section of the published article. Methods
 overview: We measured morphometric and meristic traits
 for sidewinder rattlesnakes (Crotalus cerastes) captured at the Barry M.
 Goldwater Range near Yuma, Arizona, USA during June and July 2016. We then
 used two high-speed video cameras to record locomotor trials for for 66
 individuals. We digitized a subset of videos using using the MATLAB
 programs DLTcal5 and DLTdv5 (Hedrick, 2008), choosing that subset based on
 trial quality (whether the snake performed multiple sidewinding cycles
 without stopping and turning), video and calibration quality, and
 representation of snakes from the entire size range of both sexes. We
 smoothed the data and extracted kinematic variables using custom MATLAB
 programs written by co-author BMS. The final sample for kinematic analysis
 included one representative trial for each of 26 individuals.
description: The morphology dataset includes 74 individuals, a subset of which
 are included in the kinematic dataset. It has some missing values for four
 individuals. File name: Tingle_et_al_2022_1_morphology.csv
 The file of kinematic data output from the authors' custom
 MATLAB programs includes multiple trials per individual. Some of those
 trials have missing data. We ultimately chose one representative trial for
 each individual for statistical analayses, based on completeness of data
 and number of sidewinding cycles completed without stopping or turning.
 File name: Tingle_et_al_2022_2_kinematics_sand_2.0b.csv
 The cleaned up data file of representative trials with their
 associated morphological measurements includes some outlier values that
 were removed prior to statistical analyses (see published article for
 details). File name:
 Tingle_et_al_2022_3_full_data_representative_trials_1.csv
 The DLTdv5 output files include all output for all trials that
 were digitized, some of which were ultimately discarded (four files per
 trial; 344 files total). The *_xyzpts.csv files are the ones that were
 processed in the author's custom MATLAB programs. File names:
 Tingle_et_al_2022_4_DLTdv5_output_*.csv