American Fancy Rat & Mouse Association

This article is from the Fall 1999 AFRMA Rat & Mouse Tales news-magazine.

Breeding & Stuff

Aborting Fetuses When Introduced To New Male

Kathy Madere, Amite, LA
QI’ve read that if a strange male is introduced to a pregnant female she will proceed to abort the fetuses she carries and mate with the new male. Is that true?

Pregnant mouse

AI have heard about females aborting their babies, but have never had problems with my rats or my mice if I happen to put a female with a different male not knowing she was already a few days pregnant.

Most recently, I put two female mice in with a new male and 10 days later they each had babies by the male they were with prior to the new male. Karen Robbins

AI have an article from one of the science magazines that says when a pregnant mouse smells an unfamiliar male, she aborts her offspring. She may also abort if separated from the original male for a few days and then is re-introduced to him as she has forgotten his scent. I believe the study was conducted on wild mice, therefore, domestic mice may not be as affected by this particular rule of nature since most of their wild tendencies have been bred out of them. It is also possible that the females we keep in our mouseries are familiar with all the scents of the resident males and, thus, suffer no consequence as there are no “new” males to smell.

This study might be something to keep in mind if you decide to bring a new male into your mousery or are having trouble with breeding. Helen Pembrook *

Updated February 14, 2015