stereotypical digging

[Nancy Palmer]

Hi,

I have a quick question.  My Pepper is constantly digging at the sides and
corners of her tank, and recently Buttercup has taken up the habit as well.  
I know it's just something that comes as instinct, but is there any way at
all to keep them from doing this??  Not only is it loud, but it's incredibly
obnoxious and I know have to move them out to the kitchen cuz it's keeps me
awake at nights.  I also find it odd that it's just my female gerbils.  
Cinnamon and his sons (in their own separate tank) don't do it and I don't
have a problem with them.  Any suggestions?

Nancy
Pepper, Buttercup, and 5 new additions
Cinnamon, Ranma, Ryoga