American Fancy Rat & Mouse Association

This article is from the Fall 2002 AFRMA Rat & Mouse Tales news-magazine.

2 Fathers sire 1 litter?

By Carmen Jane Booth, D.V.M.

Q We had a situation come up recently where two rats I had sold someone were pregnant (accident—long story) and there were two males that could possibly be the father. Each male was different enough from the females that we should have been able to tell by the coloring/markings of the babies as to who was dad. Problem is, the babies came out colored/marked as if both males sired some of each of the litter. I heard it was possible in dogs to breed your female to two different males at the same time and get puppies in the one litter that would be from different fathers (DNA would then be used to determine who sired the puppy). Is this possible in rats (or for mice for that matter), to have two fathers for one litter? I don’t remember reading it in any of my books. Thought you might have a clue on this one. Thanks! Karen Robbins, Winnetka, CA

A In any animal that has litters, it is possible if the female was bred by two males, that there could be pups from both fathers in the litter. As far as DNA testing, yes there is a place that will do parentage determination on offspring whether it is human, dog, etc. I bet that they would do it but I bet it is expensive. I don’t know the name offhand but they are located in Davis or Woodland (next town over) in California. I had a friend who worked there for a while. One of the human paternity DNA places suggested calling U.C. Davis. If you really want to know, I bet there are places that will do it. I would suggest searching under paternity testing on the Internet. I just know with what is involved, that it is likely to be $100 per rat. *

Updated March 3, 2014