Last night I was cleaning the mouse bins. One colony had 2 litters, one was just about to turn fuzzy, the other was a couple days old. For some reason, the females had apparently decided to put the babies in the food bowl instead of under the hide I give them.

After cleaning the bin, without thinking about it one way or the other, I put the pinkies under the hide, filled the food, and moved on to the next bin.

A while later, after I'd cleaned a few more bins, I noticed I was hearing lots of babies squeaking. Too much babies squeaking. By the time I located which bin it was coming from, only 2 of the babies were still intact enough to be saved.

The good news, I guess, is that I did catch one of the females in the act, so she is now in the grow up/feed off bin. When I first opened the bin, I shooed her away from the baby she was mauling, and watched for a while. She attacked 2 or 3 more babies (some of them already dead, but she attacked them anyway...) while I watched, and each time I immediately shooed her away. It definitely appeared during the time that I did this that she was doing a lot of attacking, and the other mice were running around looking freaked out, but not attacking any babies, so I'm pretty sure I caught the only culprit.