DOI: 10.5061/dryad.hmgqnk9q5
title: Effects of ingesting large prey on the kinematics of rectilinear locomotion in Boa constrictor

description: Large and stout snakes commonly consume large prey and use rectilinear
 crawling, yet, whether body wall distention after feeding impairs
 rectilinear locomotion is poorly understood. After eating large prey
 (30-37% body mass), all Boa constrictor tested could perform rectilinear
 locomotion in the region with the food bolus despite a greatly increased
 distance between the ribs and the ventral skin that likely lengthens
 muscles relevant to propulsion. Unexpectedly, out of eleven kinematic
 variables, only two changed significantly (P&lt;0.05) after feeding:
 cyclic changes in snake height increased by more than 1.5x and the
 longitudinal movements of ventral skin relative to the skeleton decreased
 by more than 25%. Additionally, cyclic changes in snake width suggest that
 the ribs are active and mobile during rectilinear locomotion particularly
 in fed snakes, but also in unfed snakes. These kinematic changes suggest
 that rectilinear actuators reorient more vertically and undergo smaller
 longitudinal excursions following large prey ingestion, both of which
 likely act to reduce elongation of these muscles that may otherwise
 experience substantial strain.
description: # Effects of ingesting large prey on the kinematics of rectilinear
 locomotion in *Boa constrictor*
 [https://doi.org/10.5061/dryad.hmgqnk9q5](https://doi.org/10.5061/dryad.hmgqnk9q5) Corresponding Author: Jarrod Petersen, Brown University, [jarrod_petersen@brown.edu](mailto:jarrod_petersen@brown.edu) Principal Investigator: Thomas Roberts, Brown University, [thomas_roberts@brown.edu](mailto:thomas_roberts@brown.edu) ## Overview and General Information This dataset consists of only one type of file which has X and Y marker coordinates obtained from point tracking of light videography. There are at least three trial files per individual (n=6) and sometimes there are more. The "bc00" prefix lists the ID number for the snake which can be referenced to the tables in this document and "PRE" & "POST" refer to the feeding condition (either before or after, respectively). From these coordinates, all of our variables were calculated using simple equations described in the manuscript. Data was recorded at 30 frames per second and the videos were stopped when the snake stopped moving, so each video is not the same length. **All numerical values are in millimeters**. For further detail on our methodology and for a supplementary video, please refer to our manuscript published in The Journal of Experimental Biology. Importantly, the following two rules describe how this coordinate data should be treated. * For a y-coordinate, a more dorsal/superior point will have a lower numerical value than a more ventral/inferior point which would have a higher numerical value. * For an x-coordinate, a more cranial point will have a higher numerical value than a more caudal point which would have a lower numerical value. ## Data-specific Information For each file there are 16 variables describing the X and Y positions of eight markers, the description of these variables and markers is as follows: 1. **marker001_cam1_X, marker001_cam1_Y**: Marker 1 is the most dorsal point that is located on a piece of tape sitting just above the most dorsal part of the snake body. X and Y represent the X and Y coordinates of marker 1 over time and cam 1 indicates the camera on the lateral plane. 2. **marker002_cam1_X, marker002_cam1_Y**: Marker 2 is the second most dorsal point that is located superiorly on dorsal scale row within the range of 17-24. X and Y represent the X and Y coordinates of marker 2 over time and cam 1 indicates the camera on the lateral plane. 3. **marker003_cam1_X, marker003_cam1_Y**: Marker 3 is the third most dorsal point that is located superiorly on a dorsal scale row within the range of 11-16. X and Y represent the X and Y coordinates of marker 3 over time and cam 1 indicates the camera on the lateral plane. 4. **marker004_cam1_X, marker004_cam1_Y**: Marker 4 is the second most ventral point that is located inferiorly on a dorsal scale row within the range of 6-8. X and Y represent the X and Y coordinates of marker 4 over time and cam 1 indicates the camera on the lateral plane. 5. **marker005_cam1_X, marker005_cam1_Y**: Marker 5 is the most ventral point that is located inferiorly on dorsal scale row 3. X and Y represent the X and Y coordinates of marker 5 over time and cam 1 indicates the camera on the lateral plane. 6. **marker006_cam2_X, marker006_cam2_Y**: Marker 6 is located on the underside/belly of the snake on the cranial-most ventral scute of a three-scute-pair. This scute pair is directly underneath markers 1-5. X and Y represent the X and Y coordinates of marker 6 over time and cam 2 indicates the camera on the ventral plane, looking up from below at the underside of the snake. 7. **marker007_cam2_X, marker007_cam2_Y**: Marker 7 is located on the underside/belly of the snake on the caudal-most ventral scute of a three-scute-pair. This scute pair is directly underneath markers 1-5. X and Y represent the X and Y coordinates of marker 7 over time and cam 2 indicates the camera on the ventral plane, looking up from below at the underside of the snake. 8. **marker008_cam2_X, marker008_cam2_Y**: Marker 8 is located on the lateral skin of the snake at a marker located approximately at the midline. X and Y represent the X and Y coordinates of marker 8 over time and cam 2 indicates the camera on the ventral plane, looking up from below at the underside of the snake. This marker is exclusively used to measure cyclic changes in muscle width (∆W). As some markers (2-5) give a range of dorsal scale rows they were attached to, a complete list per individual is below: | | bc04 | bc04 | bc06 | bc06 | bc08 | bc08 | bc09 | bc09 | bc10 | bc10 | bc11 | bc11 | | -------- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | | | Pre | Post | Pre | Post | Pre | Post | Pre | Post | Pre | Post | Pre | Post | | Marker 2 | 22 | 17 | 20 | 20 | 18 | 17 | 21 | 21 | 20 | 21 | 17 | 24 | | Marker 3 | 12 | 11 | 13 | 14 | 12 | 12 | 14 | 12 | 13 | 14 | 11 | 16 | | Marker 4 | 8 | 7 | 8 | 8 | 8 | 7 | 8 | 7 | 7 | 7 | 7 | 6 | | Marker 5 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 |