Distinct morphological drivers of jumping and maneuvering performance in gerbils
Data files
Feb 06, 2025 version files 9.23 MB
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binomial_turn_data.csv
2.25 KB
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jumpdata.csv
7.90 MB
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maneuverability_tracing_data.csv
1.29 MB
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ManeuverabilityData.csv
24.02 KB
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pixel_scaling.xlsx
9.32 KB
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README.md
5.12 KB
Abstract
Theoretically, animals with longer hindlimbs are better jumpers, while those with shorter hindlimbs are better maneuverers. Yet experimental evidence of this intuitive relationship is lacking. We experimentally compared jump force and maneuverability in a lab colony of Mongolian gerbils (Meriones unguiculatus). We hypothesized that gerbils with long legs (ankle to knee) and thighs (knee to hip) would produce the greatest jump forces, while gerbils with short legs and thighs would be able to run most rapidly around turns. Consistent with these hypotheses, gerbils with longer legs produced greater jump forces after accounting for sex and body mass: a 1-mm greater leg length provided 1 body-weight-unit greater jump force on average. Furthermore, gerbils with shorter thighs were more maneuverable: each 1-mm greater thigh length reduced turn speed by 5%. Rather than a trade-off, however, there was no significant correlation between jump force and turn speed. The experiments revealed how distinct hindlimb segments contributed in different ways to each performance measure: legs to jumping and thighs to maneuvering. If variation in jumping and maneuvering influences survival during predator encounters, then hindlimb segment lengths may be subject to strong natural selection.
https://doi.org/10.5061/dryad.hdr7sqvqd
Jump Force Data and Code
Dataset: jumpdata.csv
Script: Jumping_Code.Rmd
This dataset and script allow you to test for correlations between gerbil traits and jump performance. The columns contain identifying information on each trial -- "Trial.ID", "Date" -- identitiy and trait information for each gerbil during that trial -- "Gerbil.ID", "Sex", "Mass.g", "Hindfoot.mm", "Leg.mm", "Thigh.mm", "Forefoot.mm", "Arm.mm", "Tail.mm". For each trial, "Time.ms" represents the timepoint in the trial in ms. "Input0" to "Input5" give the raw output from the force plate for the 6 inputs. "Vx", "Vy", and "Vz" give instantaneous velocity in the X, Y, and Z directions. "Vxfilt", "Vyfilt", and "Vzfilt" give instantenous velocity in each direction after running the filter. "Ax"..... and "Fx"...... give instantaneous acceleration and force, respectively, in each direction with and wihtout the filter. "AbsFx" to "AbsFz" takes the absolute value of filtered force for use in calculations.
Maneuverability (Corner-Turning) Data and Code
1. Determining corner-turning speed from video tracking data.
Dataset 1: maneuverability_tracing_data.csv
Dataset 2: pixel_scaling.xlsx
Script: Manueverability_Tracking_Code.Rmd
This dataset contains the movement-tracking datapoints for every video for which a gerbil turned the corner. The "Trial.ID" column contains the unique identifier for each trial (e.g., G2_T1_135d_03Jul2022), including the gerbil ID, trial #, turn angle, and date. There are also unique columns for "Date", "Turn.Angle", "Gerbil.ID", and "Sex". The columns "Coord.X" and "Coord.Y" represent the position of the gerbil's nose in the camera view based on tracking in DLTdv8.
Run the script "Manueverability_Tracking_Code.Rmd" to visualize the gerbil's trajectory and calculate speed around the turn for each trial in the dataset.
Use the dataset pixel_scaling.xlsx to determine the number of pixels per centimeter for each date and turn angle, which is needed for the maneuverability tracking script.
2. Testing impacts of sex and turn angle on probability of turning a corner.
Dataset: binomial_turn_data.csv
Script: Corner_Turning_Probability_Code.Rmd
This dataset and script allow you to run a bionomial regression to test whether sex and turn angle are significantly associated with the probability of turning the corner at least once at a given angle. This script also contains code to plot the results.
3. Testing impacts of traits, sex, and turn angle on corner-turning speed.
Dataset: ManeuverabilityData.csv
Script: CornerTurningAnalysis.Rmd
This dataset and script allow you to run generalized linear mixed models to test for significant impacts of traits, turn angle, and sex on corner-turning speed. The columns contain basic information about each trial -- "Date", "Trial.ID", "Turn.Angle" -- and identify and trait information about each geribl -- "Gerbil.ID", "Sex", "Mass.g", "Hindfoot.mm", "Leg.mm", "Thigh.mm", "Forefoot.mm", "Arm.mm", "Tail.mm". The last three columns describe the results of the trial. "Turn.Speed.mps" gives the speed around the turn in meters per second. "Top.Turn.Speed" indicates whether the trial is the best performance at that angle for that gerbil. "Notes" describe the gerbils behavior during the trial. This script also contains code to plot the results.
Testing for a trade-off in jumping and maneuvering performance
Dataset 1: jumpdata.csv
Dataset 2: ManeuverabilityData.csv
Script: Performance_Correlation_Code.Rmd
This script tests for a correlation between jumping and maneuvering performance using the jumping and maneuvering datasets described previously.
Videos
Video_S1.mp4 -- Example of a strong jump. Video shows male gerbil’s feet being sprayed with compressed air. He responds by hopping on all four feet, resetting on his hindfeet, and performing a jump. This was the strongest jump in the dataset, producing a force of 10.8 body weight units.
Video_S2.mp4 -- Side view of male gerbil maneuvering around 135° turn. Gerbil approaches the end of the corridor, receives the compressed air spray, turns around, and sprints down the corridor and around the corner. He completes the turn and continues with his body parallel to the slow-down corridor.
Video_S3.mp4 -- Top view of female gerbil maneuvering around 90° turn. Gerbil sprints down the corridor and around the corner. She completes the turn and then stops with her body parallel to the slow-down corridor.
Video_S4.mp4 -- Top view of male gerbil maneuvering around 45° turn. Gerbil sprints down the corridor and around the corner, slowing down as he turns. He completes the turn and then pauses with his body parallel to the slow-down corridor before continuing to run to the end.
Video_S5.mp4 -- Top view of female gerbil on 90° turning assay. Gerbil sprints down the corridor and stops in the corner without rounding it. She explores and tries to climb over the wall.
Jumping data
To test jump gerbil performance, we built a vertical tunnel (10x10x47-cm) using clear 1/16-mm polycarbonate sheets, including a ~0.5-cm gap at the bottom, and designed to not exert weight on the ATI mini40 force plate. We placed gerbils in the tunnel to acclimate for 30 seconds and set the force plate to record data at 1,000 samples per second using Igor (v7, Wavemetrics, Lake Oswego, OR, USA). Each trial began when gerbils stood on four feet and were sprayed with compressed air to simulate surprise by ambush predators. We recorded videos at 700 fps using two Phantom MIRO cameras and Phantom Camera Control software. To increase chances of measuring maximum jump force, we completed 2-4 trials for 20 gerbils (N = 12 males, 8 females); we stopped after 1 trial for 8 gerbils that exhibited stress (N = 2 males, 6 females). We scored each of 57 trials involving 28 individuals as a: (i) ‘jump’ in which the gerbil pushed off the ground vertically using its hindfeet, (ii) ‘hop’ on all four feet, or (iii) any ‘other’ response. We obtained time-matched morphological measurements for 15/17 of the gerbils who jumped (N = 11 males, 4 females), and the trials for which we recorded jumps are included in the attached dataset. We calculated maximum resultant force from the vector sum of forces in the x, y, and z directions and expressed this value in proportion to the gerbil’s mass. We low-pass filtered force plate data at 70 Hz to account for vibrations. Resultant force outputs were given in body weight units (BWU); a BWU of one is equivalent to a jump force of 1x body weight. We used the maximum force recorded for each gerbil for analysis.
Maneuverability data
To quantify gerbil maneuverability, we conducted corner-turning trials. We built polycarbonate corridors of increasingly difficult turn angles (135°, 90°, 45°) with a 120-cm runway into the turn and 80-grip black traction tape to line floors and visually indicate turns. Gerbils acclimated by exploring the corner and back at least three times before we sprayed them with compressed air to begin the trial. We recorded runs at 240 fps using GoPro Hero 10 Black cameras (one above the arena; one lengthwise along the runway). We ended up using the top camera view for analysis, and the tracking data from that camera are included in these datasets. We tested each gerbil up to three times on the three angles, allowing >48 hours between tests and randomizing the order of angles. We categorized each of 226 trials across 29 individuals (14 male; 15 female) as a: (i) ‘turn’ if the gerbil’s body was perpendicular to the lane after the turn (47.8%) (ii) ‘no turn’ if it stopped before its body was perpendicular (50.9%) or (iii) ‘fail’ if the gerbil ran into a wall (1.3%). We excluded failed trials from analyses, along with 15 trials for which a camera malfunctioned and 3 for which we did not have timely trait measurements. The final dataset included 192 trials across 28 individuals (N = 63 for 135°, 65 for 90°, 64 for 45°).
To calculate turn speed for each maneuverability trial, we tracked the tip of each gerbil’s nose through the trial using DLTdv8 in MATLAB R2022a to calculate instantaneous velocity using trajr and used filter order 3 with a filter length of 21 to smooth the trajectory. We calculated the average speed around the corner over 0.1-s intervals. The fastest turn speed was selected for each gerbil and angle, yielding 52 top-performance trials across 24 individuals (11 males, 13 females).
- Reed, Courtney; Swartz, Sharon; Littleford-Colquhoun, Bethan et al. (2025). Distinct morphological drivers of jumping and maneuvering performance in gerbils. Zenodo. https://doi.org/10.5281/zenodo.10428391
- Reed, Courtney; Swartz, Sharon; Littleford-Colquhoun, Bethan et al. (2025). Distinct morphological drivers of jumping and maneuvering performance in gerbils. Zenodo. https://doi.org/10.5281/zenodo.10428390
- Reed, Courtney G.; Swartz, Sharon M.; Littleford-Colquhoun, Bethan L. et al. (2025). Distinct morphological drivers of jumping and maneuvering performance in gerbils. Journal of Experimental Biology. https://doi.org/10.1242/jeb.250091