I found out what was killing the babies. We had a rat in the building and it was eating them. Actually it was one of my pet rats that had escaped from a hutch I was keepign them in outside. Needless to say, this rat won't live much longer. Next time dad goes outside he's going to take care of it.
Am trying to think how to word this without seeming too harsh.
I would be totally distraught if a rat ate any of my buns, but it isn't really the rat's fault - he or she was just acting according to instinct. As the rat is a pet couldn't you just ensure the hutch s/he is in is escape proof so it doesn't happen again?
I don't have pet rats but killing a pet rat because s/he was just being 'a rat' made me feel really sad.