Here's a picture of Pandora with the twelve points that I tracked marked with a red dot.
Following is a graph of the body angle of four successive points along Pandora's back that are anywhere from 3-5 inches apart. (Taken from Video 01.)
Note that all the angles oscillate around 180 deg. Also, it is interesting that there is a phase difference of about 3.5-4.5 frames between the different points along the snake. (2 frames = 1 second). That seems to imply that there is a propagation of muscle activity, and thus neurons firing, along the body of the snake that also follows a similar model.
Watching the videos it's interesting that Pandora seems to utilize all four types of snake locomotion: serpentine or lateral undulation (what you normally think of when a snake slithers); concertina (think inch worm); rectilinear (when the snake moves in a straight line by picking up its ribs, moving them forward and then setting them down); and sidewinding.
One interesting combination that she often used was to sidewind with the front three quarters of her body to position herself in front of something while leaving her back portion stationary. Then she would pull the back portion forward like a sideways inch worm and push herself towards her goal using concertina motion. This tactic is very apparent in Video 03.
The use of sidewinding into concertina and back to sidewinding seems to be a preferred way of getting around for a large snake that is limited to a small area. I would be very interested in performing a similar experiment on a garter snake which I suspect will move with a purer form of serpentine motion and will have more space to move freely. I would also like to experiment with ways of attaching tracking points along the body of the snake. I don't think taping pieces of paper would be very animal friendly as adhesives could rip off scales or cause some other damage to the snake.
Let me know if you have any comments or suggestions.
Oh, and special thanks to Nicole and Alex for letting me borrow their snake for a couple hours.
Video 01
Video 02
Video 03
Video 04
Video 05
Video 06
Video 07
Video 08
Video 09
Video 10
Video 11
Video 12
Video 13
