I thought this would be more of a funny titled thread than anything but since we are taking guesses and I got it started I will go initially with exercise. I can imagine that moving from the home enclosure to another will involve more exercise and that can help move the digestive process along much like a human going on a distance run.

Another thought would be that the animals leave a chemical trace, phermones or otherwise, that allows other snakes to know that the area is already inhabited by another. Cleaning the tub could remove the scent and signal to the animal that it would be advantageous to "mark" the territory.

There are my two softballs, I could go to the research databases but I spend enough time doing that for my own research and prefer to take breaks on the weekend