[souffle]

I expect it is pee. Young hamsters don't wee very much as they are adapted for living without much fluid. The urine is thick and concentrated in hamsters and doe dry quite like limescale as the urine has lots of crystals in it. I wouldn't worry about it too much if your hammy is eating well and you give some fruit and veg now and again. Check the bottle daily for free flowing and maybe add a small bowl of water in case your hammy prefers that. It's more a worry if they wee a lot as that can mean diabetes.