[quote=Raxacoricofallapatorius]
I once had pet mice. 2 of them. 1 died so I got 2 more to keep mine (the other was my sister's) company. They lived for a while then died. Mine was old by this time so I figured she'd just die, but she didn't, she kept on living, so I got another one, and they got along really well. Then one day the young new was was dead, and I think that she may have killed it.But we'll never know. Maybe she killed all of them. It will forever be a mystery, because she finally died, we'll never get to ask her.
[/quote]

I had a mouse once too, but he lived alone. Rats, and probably mice, too, (especially female ones) are known to kill ones they feel are threatening their territory, especially if they are too young to defend themselves or just old enough to be determined a threat.