I guess I am a little confused, so this may be a dumb question, I know that if you brumate them they will burrow, but aren't they still somewhat active in brumation? The only animal I have brumated was my skinks so it may be completly different, but even though they were brumating there were still somewhat active and move around the cage from time to time, drink water etc, which is why I would think you would still want to provide a larger cage for them. Is this not the case with Tegus? Mine didn't brumate last year so I haven't had any experience with this yet.