Pregnant mouse?

[Tsubaki]

Mice eats their young due to extreme stress or a serious protein deficiency, if simply being alone or with unfamiliar mice got them to eat their young they woulndt be as effective as a species. 99/100 times young get eaten, wrong type of feed. My source for this? I bred fancy mice for years, and only had accidents the first few months untill I figured out pregnant mice needed supplements. Aka animal protein, insects (dried or not) or dried meat.. or even high quality (high protein low sodium) cat food works. Without supplements there's always a chance of the mother culling the litter because she can't spare the protein the babies are made out of, they aren't vegetarians after all. Rats do the same. I could even sort of, count, and sex the newborns without losing any. They did sometimes clean out the weak ones though. Only other problem is if you put a nursing mom with a non nursing possesive female, that would steal babies and blocks the mothers acces causing the babies to lack nursing. Males fighting isn't anything you can do about, it takes a long time and serious dedication to breed friendly males that can live together. If store bought mice fight, they will not very likely stop.