Thanks for all the input. I went ahead and lifted the hide and counted them later that day. There were 13 of them! Later in the day I counted 12, and then today I found 11, and a half eaten one, in the nest. Maybe 13 was too many for her? She hasn't seemed to mind me handling them, even when she is in the nest. She's a really sweet gal, but has one quirk. If you put your finger at the top of the wire mesh, she will attack it ferociously. She does this to any object placed there. I first noticed this a few weeks before the birth, so I don't think it's related to pregnancy. I've never fed them through the lid, and first noticed this behavior before I added a food hopper that hangs from the lid. Perhaps some rats just have an instinct to attack/bite things through wires? She's a pet store rat that lived in a glass enclosure there, so I can't imagine it's a learned behavior. The other two just come up and sniff your fingers and maybe nibble extremely lightly. Other than this she has shown absolutely no signs of aggression.