I had a female give birth to a litter of 20. I had separated her from the male and the rest of the colony because I wanted to separate her young for holdbacks, and in the colony I had no way to know which were hers.

I took some of them as they were growing to feed to my corns, but she raised about 13-15 of them to weaning just fine, and without any help.

She is a black & white spotted, so it isn't only the white lab mouse strains that can have big successful litters.