As some of you know I have two ferrets, one is 20 or so weeks old, the other is 8 months. They were using the litter great when I got them and then for a few weeks afterwords but now they have stopped using the litter. They use it when there on the bottom level playing, but they sleep on the top level (The cage is three levels) and then when they wake up they go to the washroom on the second level. I've tried moving the food and water up to the second level to discourage them.. but it hasn't been working. I've also cleaned the second level and even switched the actually level around (Top went to the middle, middle to the top) and they still are using the second level as a bathroom. Any suggestions on how I can stop this?

The level is not big enough to stick there litter pan up there..

Thanks for any help!