When do hamsters become sexually mature??

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Water bottles are better. Drill a hole in the side for the spout and two holes above it a good bit higher. Thread cord elastic through the two small holes, push the spout through and loop the elastic round the bottle to hold in place
Make a wire mesh roof for the bin so it's nice and airy. They will only be in there for a few weeks so you don't need anything fancy. Just be sure they are secure and away from any other pets and cannot climb up on anything to reach the roof mesh.