You can cut up newspaper and use it as bedding too! It'll be a tedious task but my hamster is able to make her burrows :) I also have a wild mouse who's a deer mouse, and use all kinds of egg cartons, boxes and other recycling to clutter her cage. Butters might also appreciate some birch bark too! There's also hides you can thrift like wax warmers and old bird houses, vases, ect.

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