LOL I just had to respond to this one! I have had two rats, over time, who - when I'd transfer them into a small (wire) cage for traveling (these would be the rats that also "worked" part time as classroom pets) would immediately begin weaving strips of shredded tissues into and around the top of the cage. I'd put them into the cage, place them in my car, and by the time I arrived at school, the cage looked like it had been festooned with party streamers!
The best reason I could come up with was that rats/mice are animals who, in the wild, most likely would live in burrows or narrow, low enclosures.... so now, when given the opportunity (such as being in a cage that had a 'ceiling' low enough for the animal to easily reach it), they'd try to pad the ceiling just as they do the bottom of the cage.
It could very well be a response to stress, but could also just be an instinctual behavior.
It's far too easy to anthropomorphize with these critters, though, for me anyway, and by golly we sure had a good laugh every time these rats would start in with their interior decorating!
=)
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Rebecca
TSBabe66@hotmail.com
Honored to moderate at Snakefeeders, a great place to buy/sell/trade feeder animals. Come check us out! http://groups.yahoo.com/group/snakefeeders/