Cloaca Opening?

My unsexed Pastel, whom I have been assuming is male because of the length (3 ft) has been climbing around his cage. I take him out to handle and his(or her, whatever), cloaca was open. It seemed to be opening and closing based on the movement of the snake. Any insights? There does not appear to be an injury.

It might have been feeling nervous and preparing to pee on you if you got too frightening. :)

Always check for "sausage butt" before handling as well as the movement can ...er.... get them pooping.