Just as an aside, the tub that my juvenile normal is in has molded "handles" on either side of the tub, with just enough gap between there and the lid for him to squeeze into... sometimes he will squeeze his way up there, and hang, with his head resting on the substrate, and his body through that little tunnel, tail hanging down, for hours and hours at a time. If your husbandry is right, my guess is that they are trying out new "hunting spots" and waiting for a rat to run by .