Heres the story...
I had a tank set up with 1.4 mice. One of the females appeared to have been picked on by the male, she had scabs on her back. So I removed the male and put him in a separate enclosure.
3 days later, 3 of the 4 female mice ganged up on the one female that had been picked on and killed her. They ate her head and her belly (all of these mice are full grown). To top it off, they left her in the food dish, quite a gruesome sight.
The mouse that they killed seemed to be different in only one way from the 3 that committed mousey murder. She did not appear to be pregnant like the other 3. The mice had plenty of food (high in protien) and lots of water.
Also these mice had been living happily together for about 3 weeks or so with no aggression signs other than what I thought to be the male mouse recently picking on her.
Any suggestions as to why this might have happened? Has this happened to anyone else?