This article is from the WSSF 2015 AFRMA Rat & Mouse Tales news-magazine.

By Karen Robbins

Jill, OH, e-mail
Q I have a question which has not been addressed online or in conventional mouse genetics books (which all deal with M. musculus). I have also checked Ann Vole’s excellent website.

I would like to know if the offspring between a deer mouse female (P. maniculatus) x house mouse male are fertile, or, because they are cross-genus hybrids, are they sterile (such as mules)? I read this on Ann Vole’s website where she says she had house mice, deer mice, and the progeny of those which she called half-wilds. Some of their other observations regarding deer mice seemed accurate enough: they really do seem like miniature gerbils on the hyper setting, they will very gradually habituate to humans observing them from a foot away, and they are most definitely escape artists: I had to live trap my oldest girl 3 times!

Basically, if I breed a house mouse male to a deer mouse female and I keep the pups back, should I be keeping them strictly for pets—if they are sterile—or should they be raised as breeders/foundation stock if they are fertile?

Both horses and donkeys are in the same genus, Equus, and yet their offspring are usually (~98% of the time) sterile. Deer mice and house mice are completely different genera, but it’s reported that they can interbreed and have viable offspring. The offspring are reported to lose their white bellies; other then that, very little is published or known. Nobody has reported on the fertility or fecundity [ability to produce offspring] of the half wild offspring.

I really ought to go to PetSmart and get a male mouse just to try this out, but I’d rather not bring excess mouse-lives into the world without good homes for them first, you know? (and if they are intended to be breeders, they would not make good pets, they’d be too shy). So it’s better to ask, then to try, for now. Please let me know, or please direct me to someone who might know. This has, so far, been a delightfully scientific thought-cluster.

A I sent this to our vet who works in the lab/research setting since they keep deer mice in labs, and this is her reply:
I think it comes down to chromosome number. M. Musculus have 40 chromosomes. Peromyscus have 48. If you could get any progeny, they would be sterile. I think that the chromosome number is too different to get viable offspring. I don’t know of any hybrid being produced in the research arena. Carmen Jane Booth, D.V.M., Ph.D.

I did some research on my own and found Peromyscus subspecies do not interbreed, plus they are a totally different family and genus from house mice. You can check the following sites for more information.

• Peromyscus on Wikipedia
• University of Michigan Museum of Zoology
• University of Michigan BioKIDS
• Science Literature: Rapid adaptation in deer mice

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