I understand this is a normal behavior, but my rat Mindy gets pretty intense with it. She just started tearing up the newspaper under the bedding and dragging it under their hat (there favorite bed, consists of a towel and an old ball cap). Well last week I cleaned her cage and she looked almost distressed that her newspaper was gone... well I felt bad tonight being christmas eve and all so I saved a few pieces of newspaper and put in under the clean hat and new towel... she instantly livened up and hurried to tuck the pieces of paper under a fold in towel. If you knock a piece of paper down she'll sprint down to the bottom level and pick it back up. I have made a habit of tossing a piece of newspaper in there for her and she drags a huge strip and slowly breaks it down in the nest... it's kinda funny. Does anyone have any info on nesting... what triggers it? In heat? Colder weather? etc?