Rat language?

So I didnt put this in the breeding section since I have no intention of breeding, at least at this time..
He was kind of an accidental pet, bought for feeding purposes then he ended up being to sweet and now hes a pet -.-;.

So having never owned a rat before I had a couple questions about what it means when they do certain things.
Such as teeth chittering, light finger nips, massive pooping when hes initially taken out of his cage O_o. Never seen so much poop come out of something at one time and I used to own guinea pigs. lol.

For the most part he just sits with me and atleast tolerates being pet. I know as a feeder he probably wont live long given the general rule of questionable genetics, but atleast I can give one a few good years of comfort for all the f/t ones I feed to the scaley pets :D.

The "poop machine gun" is a kind of defense mechanism thing. Teeth chattering, or "bruxing", as it were, is usually done when the rat is contented....however, I think they may also do it sometimes when they're scared. And with finger nips, you may want to make sure you have no food smells on your fingers.....he may want to test their "edibleness"...

oK.. so hopefully the bombardiers will stop once he gets used to being handled. Thank goodness.
I figured the nips might be some tasting, though I wasnt sure if rats give kisses like guinea pigs do so wasnt quite sure.

thanks for the info