So i was thinking..

I think she's either smelling the mouse, or picking up the vibrations. Anytime I walk up to our tubs, Omicron always pops out to see what's going on. Snickets doesn't so much, I think she's more used to it.

When I pre scent I put the bag/box on top of their tubs, and once Snickets hears something be set down on top of her tub, she knows it's feeding time. Along with smelling it, of course. Little Omicron is getting used to it, but he knows just by smell so far.

Mine just know when it's feeding day, and are usually waiting with their noses pressed against the tubs... starting the night before. :P:D

Who knows if they recognize the bag or just smell the mouse? It would be interesting to do the suggested experiment, though. I know my old cat used to recognize Burger King bags specifically (I ate a lot of fast food back then) - not McDonald's, not Taco Bell, just Burger King, because I always got the chicken sandwich she loved. And even if got something besides that sandwich, she'd always perk up at the sight of a BK paper bag. So who's to say a snake can't have that ability too? :weirdface