do you feed your animal in the same tank you house him? if you do i would try feeding him in another location like going to wal mart or some place where you can pick up a large plastic tub or even find a large box and take him out of his tank, or what ever you have him in, and try feeding him in that. as a personal preference, and i have this luxury, i never feed my animals in the place where they reside and i have never had a problem with any of them eating in the six years i have had them. when i take them out and put them in their tub they know what time it is, time to dine. maybe he wants a little privacy? also think back and remember about the size of the animal you fed him last time and try some thing a little smaller. some times animals may get a little traumatized by the size of the previous meal, just some thing to keep in mind. you mentioned rats, any thing at this point is worth a try in changing his food. you also have to take into account that it is winter time, even though you mentioned he had never done this before, and some times as they get older there habits change. as long as you are watching his weight i would not get overly worried.