Just looking for some input here from you rat breeders. We have a female rat that's been raised with us (not a new purchase). She was always a bit nippy but suddenly she's become impossible. She's on her 2nd litter which are currently pup sized (just shy of weaning age).

She became very aggressive with us when she was in with the breeder male and even more so as her pregnancy progressed and after the litter was born. To the point of extremely hard bites for both Mike and I. She has to be physically blocked from getting to us when we feed or water her. This I could deal with however she's now turned that aggressiveness on her own litter.

She's killing them, one every few days! I kept finding a dead pup but not a mark on it and wondered if they were genetically inferior pups. I finally caught her at it last night. She had a perfectly healthy pup in her mouth by it's hip area and was flinging and shaking it, even almost cartwheeling with it in her mouth! I've never in my life seen such behaviour from a female rat. It was highly disturbing to me and I've removed the remainder of her litter to another female who is nursing and has accepted the foster pups.

We will euthanize this female today as I can't have her killing healthy pups plus I like to breed calm, good natured adults. I've just never seen a female turn like this for no reason at all. Nothing has changed in her daily routine, feeding, etc. This was not a particularily big litter to stress her out. I'm just stumped as to why she'd go from a sort of grumpy rat to this horrible aggressiveness to us and her own pups.