This article is from the WSSF 2007 AFRMA Rat & Mouse Tales news-magazine.

By Carmen Jane Booth, D.V.M. Ph.D.

Rachel Eyre, e-mail
QMy name is Rachel and I’m emailing to ask a question on mice for some research I am doing for my studies. I’ve heard that dominant male mice can suppress the testicular development of the juveniles in his social group. Can I ask if this is correct, and if it is correct then why does he do it? Is it so that he is more likely to mate with the females? Could you please help or at least point me in the right direction for finding information?

AWe haven’t heard of this and could not find out on searching the database for published articles. Who are you doing the research for? Is this a class project and for what grade? Where did you read this or get your original information from?

Kelli Boka, Santa Clarita, CA
QI just had two pet mice neutered and was told they can still have sperm for 2 weeks after the neutering. Also, that females can hold sperm for 2–3 weeks before they become pregnant. I’ve heard of this in hamsters where the females can be with males then separated for several weeks then suddenly become pregnant. I know in rats and mice there is the delayed pregnancy when a female gets bred immediately after delivering that she won’t deliver for 4 weeks instead of the 3 weeks. Is this correct?

AIn general, in any species after a neutering or vasectomy, you have to wait because sperm do survive in the vas deference. As for the females holding sperm, some rodents do this, but I am not sure about mice. I emailed this to one of my friends who is the manager of reproductive services at The Jackson Laboratory. She says, “ I can tell you that there will be a few from good sperm samples that are still alive after 24 hours in the IVF drop . . . not many and they are not very lively but still moving.” There is just nothing on females holding sperm.