Mice/Pregnant female Eaten!!!
I have a small breeding collection of mice that are used for a couple of picky snakes as well as newborn snakes which sometimes will only take live for the first feeding or two, but the main question is I give my mice 2 blocks of food per mouse every day but one of my females was definitely pregnant and had had "I ate a golf ball" look one night so I decided to check on her the next day to clean the cage before the babies came but by morning the other females or maybe the male had killed and partially eaten her. All the females were raised together and the male had only been in there about a week and other than normal breeding squeaks I never saw any signs of anything abnormal. Just wondering if it would safe to try breeding them or if I should just start over with different new mice. None of them have ever had babies before, if that helps.
Well...that sounds terrifying. I am very sorry you had to see that.
It could have been the females or the male. To be honest, I'd recommend two things: waiting 2-3 weeks before pairing anyone else up, and revising your breeding arrangement.
The reason I suggest waiting is that for the surviving mouse, regardless of the events that led to the death, this situation will have undoubtedly been very traumatic. Traumatized mice have lower immune systems (and pregnant/nursing females cannot be given normal medications), as well as lower successful breeding and birthing rates. Anxious or upset females may cannibalize pups. It is safer to wait until all have recovered and grieved.
As far as your breeding system, please allow me to respectfully suggest the following arrangement:
Breed one male to one to two females at a time, leaving them in the same cage (separate from other females) for two weeks. At that point, remove all three to their own separate cages. The male should NOT be kept around pups or females when not in that two week window - Males frequently see pups as competition and kill them, will continue to mate with the pregnant female after having her pups leading to serious health complications for mother and babies, and cause undue stress on the mother leading to harming pups or killing the litter immediately. Additionally, leaving the male with females when not closely supervising pregnancy leads to surprise litters which is less beneficial to a snake owner than knowing when food is on its way! It surprises me that he was only with them for a week - she would likely not have been golfball pregnant by him if that was the case, so there *may* have been something else going on with her health.
After separating all three, each mom should have her own space to nest and prepare stress-free for the birth away from other females and especially away from the male. Females DO notice when their babies go missing, so if you intend to do this in the longterm, please consider leaving 2-3 pups of your preferred gender and size with the mom so she can nurse, raise them, and provide you with more healthy breeding stock. Never handle pups where mom can see you. Breed only offspring with your desired traits (which I imagine would be litter size, offspring size, temperament, not eating the litter, and breeding success). The mom will go into labor overnight at some point between: 7 days and 21 days later (three weeks after pairing them with the male all the way until three weeks from separating them, mice take about 21 days to gestate from fertilization to birth). If no babies come by 23 days past separating them and she does not appear pregnant, she can be immediately bred again. If she DOES have a litter, you will need to give her two months from the birth to recover before breeding her once more.
Keep in mind that first time mommas tend to be a little more erratic, sometimes being confused about what to do, and may have smaller litters. Second and third litters tend to be larger, provided plenty of recovery time has been given. You might also consider free feeding the mice - they should have feed on hand at all times day and night, especially when pregnant, so they do not think that food is sparse and kill the babies as a result. You can also supplement breeding mommas with dry kitten food as treats for a boost of protein.
This new arrangement I'm suggesting not only lets you more closely control your litters, but also allows you to figure out who went homicidal, and not breed them anymore. It also reduces stress on the whole colony, which will lead to more successful breeding as well. In that sense, it might fix the problem all by itself!
Hopefully this helped, but please let me know if I can help in any other way. I can provide resources if you need advice with your colony management or breeding, too! Sorry again that you had to deal with the loss - it must be so frustrating and sad.