They can also do it if they are stressed or new mothers. I suspect that one of my female mice either didn't get pregnant the first time round, had a really small litter or ate them. We'll have to see what happens during round 2 (currently being started now ).
I had mixed the males from the 1st 2nd and 3rd litter together. The coexisted fine for over a month. The other day I put the 7 males from the last litter in with them. Almost instantly I see a twitching dying rat. It was one of the medium ones from the 3rd litter that had lived together for the past month. I took him out and fed him to Mogwai. I then sat and watched. One of the larger males looked as if to be mounting the medium males and then biting them in the neck and instantly killing them.
I expected the smaller ones to be the ones in danger. I then thought maybe one of the smaller ones may have been a female mistakenly taken for a male. I double checked, they were all males.
Once I removed that larger attacking male and all was peaceful again. He is now in the freezer, as Mogwai has had way to much ASF rats the past few days and I think he is now holding out for them
Now I know what the ball python owners are experiencing. LOL.