My friend's snake isn't eating.

[Dracen]

I said I'd ask on here about it, because I remember my snake would sometimes go weeks without eating. She's got a 1.5 year old Florida Kingsnake; he's not shedding any time soon (my snake was more hesitant to eat when he was shedding, sometimes) and is fed once a week. Usually he notices the mouse as soon as she opens his cage and tries to grab it right away. He ate fine last week, but today he didn't take the mouse at all and she's put it back in the freezer. Any idea why a snake would stop eating without warning? Admittedly it has only been once, but this is the first time he's done it, she's worried, and I remember it stretched on for a while with mine sometimes.

Thanks