Snort... Don't mind me.. I just knew what you meant about feeding.
If he's doing what I am picturing it's called Flehming(sp). This is now they suck a scent up their nostrils when they want a good whiff. No worry..
Wiktionary says flehm
- (intransitive) To exhibit the flehmen response, I.e., to draw back the lips, allowing scent to reach the Jacobsonís organ, an auxiliary olfactory organ found in many animals.