A tussle at the den?

I am currently reviewing all the footage from the dens this past spring and will have many things to share very soon (until then, you can see a new timelapse photo almost daily on our facebook page). Recently, I came across some rather unusual behavior:

What's unusual about this? Well, interactions among snakes at our dens usually look like this, where snakes just appear to be resting with each other:

So what's going on in the first video? We have never before seen any reproductive activity (male combat or males courting females) at our dens, but we think this might be combat. This timelapse video was taken at 30 second intervals, so much of the fighting action is lost. Also keep in mind, if you've never seen rattlesnakes fight, it's gentler than you might expect (not our video):

For years people thought that combat, or the so-called 'rattlesnake dance,' was courtship between males and females. Like many animals, rattlesnake combat is largely ritualistic and rarely involves biting. The goal is to topple your opponent, similar to professional wrestling (hence the twisting to be 'on top' in the above video).

For comparison, here's a male Arizona black rattlesnake courting a female:

So what do you think is going on in the timelapse video at the top of the page?