How big is he?

He could be wanting larger prey items, or he could be large enough to be starting a breeding season fast. It seems obvious, but of course doublecheck your temps - I know here in Socal the weather has been weird, and it's been throwing off my collection at home.

If he's not really losing weight, as other posters have said, I wouldn't worry too much. It's not that uncommon. Make sure you're not handling him right now, doublecheck temps, and give it time. He'll start eating again when he's ready.

-Jen