immaculate conception in rats?

I have a female rat that I got from the local pet store. when I got her she was about to explode with babies. she had her litter three days later. she has always been on the bottom tub of my rack with no other males. well the babies are almost weaned and she looks prego again. I mean bulging at the sides. well her sister at the pet shop was doing the same exact thing but she gave birth this morning to another litter. again she hasn't been in with a male since before she delivered? is it possible for rats to have two litters from one breeding? or do I have some strange mutated super rats? thanks JOHN

Asked the same question last week. I had the same situation going on. I called Adam and he said it had to be milk. Mine that did that did not have another litter. I was also hoping for a super rat to eliminate the males. LOL

If she is actually pregnant again and with her almost weaned young then most likely one of her own sons is the new daddy. Male rats can be fertile by 5 weeks of age but likely some even younger. I've never had a son impregnate mom in a maternity situation but I generally pull the litters by 4 weeks of age and seperate males from the females.

Probably her swollen with milk.

If she's indeed pregnant, I'll agree with Jo...one of her son's did it. =)