Another thing people forget or just don't know is that large meals like those rats, when digested at a high temperature, can actually rot before they begin to digest.

If they rot first bacteria causes bloat. Imagine one balloon, the rat, inside another balloon, the snake. Inflate the inner balloon until it pops with in the outer balloon and you have the right image.

This bloating can also cause regurgitation and if that occurs, with the digestive process in full swing, the stomache acid that is expelled is in full digest mode and more volitile than it would be a few days later.

It's an interesting process, the rotting before digesting. WIth one or two animals being fed there is enough room for the snake to stretch and accomodate the expanding meal but with four going, or even just a too large meal in general, regurgitation is likely.