That's spitting it back out not a regurgitation, which will be cause by a few things.About 30 minutes after taking it down, he opened his mouth wide and began moving very violently, and within a minute the rat was back out.
Too large of a prey.
The animal was disturbed
Change it's mind.
Health issue
Have you notice this type of behaviour outside from that day and feeding, the nose/rubbing, holding his head up and closing and opening his mouth?He would alternate between nose rubbing, trying to fiX his jaw, gazing straight up and perfectly still, to twisting his neck upside down with his tongue out and opening and closing his mouth like there was something stuck in there (but i didn't see anything).