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Mice/yellow mice


Timmy\'s cage
Timmy's cage  
QUESTION: Tamarah,

I am looking for a female friend for a young, tame, male field mouse (I actually asked Natasha a question about him a couple weeks ago so I'm attaching photos that I wasn't able to before). I saw a young yellow mouse on petfinder but I was worried that she would become obese due to this agouti gene that I've been finding in my research. Do all yellow mice have this gene? Are all yellow mice doomed to obesity and health problems? Thanks for your help.


ANSWER: Hi Megan,

Field mice and house mice can and will interbreed, is there a reason you want to breed them? When male and female mice are together, it can be extremely stressful for the female, which is why I suggest leaving breeding pairs together no longer than two weeks at a time. This allows them to mate (females ovulate every five days or so), but prevents back to back litters which can hurt the female, and prevents males from killing the pups. If you are only looking for companionship for Timmy, chances are that like almost all male mice, he'd rather be away from other mice.

In answer to your question, agouti is the gene responsible for the flecking in wild type coats, and is kind of that reddish brown color. While a few yellow genes can be found at that same locus (position on the chromosome), they are not the same as agouti, which is not linked to obesity.

Yellow can be expressed by a few genes:

Lethal yellow (A^Y/*)
A dominant gene rare in America. This gene, because it's dominant, will always be expressed as a yellow mouse (except when diluted completely by albinism). It does come with a higher risk of obesity, diabetes, and other factors. Mice bred by two lethal yellow parents will have smaller litters, as this gene is lethal when inherited from both parents.

Viable yellow (A^vy or A^hvy/*)
Viable yellow and hypervariable yellow are NOT lethal when inherited from both parents, meaning full size litters can be expected. However, this gene is also linked with obesity (leading to lowered fertility) and tumors. Viable and hypervariable yellow show a much wider range of yellows, reds, and even brindling! It's actually really cool. However, many yellow mice lose a little color and turn "sooty" as they molt with age.

Recessive yellow (e/e)
A lot less is published about recessive yellow, so a lot less is known about whether or not health problems may be linked. However, this gene is pretty common, and at a completely different locus (different place in the chromosomes, away from the A type genes). To look yellow, a recessive yellow mouse has to inherit this gene from both parents.  This is also prone to a wide range of yellows and a sooty appearance after molts.

I know that was a long answer, but there is a TON of great, user-friendly information on yellow genetics and a bunch more at

Hopefully I helped, and please let me know if you have any other questions or need clarification.


---------- FOLLOW-UP ----------

QUESTION: Thanks so much for your help! I actually do NOT want to breed mice but had been assured that they wouldn't be able to reproduce since they are different species. So it looks like Timmy will be a lone buck. He seems very happy now, but I was hoping he would be able to have a friend to stave off any depression that might result from being alone. I try to handle him at least three times a day and I just got him a larger tank and more toys so hopefully he'll be okay. The genetics info was very interesting. I'm a science teacher and I may bring it up when I teach genetics. Thanks again!


Hey, that's great! Mouse genetics are infinitely useful in science, I'm so glad I could help you and your students!

Yep, while I'm sure there are some exotic species that could not interbreed, many can, so best not to risk it like you said.  I get a few too many questions about accidental litters with wild mice. :)

Boy mice get along with people very well, I am sure he'll do perfectly with you and his toys!  If you ever need any help along the way, just let us know!



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I can answer questions regarding mice as pets, mouse behavior, color and coat genetics, breeding techniques, and general health questions. I can help with caging and setup, nutrition, social issues, and what to do in most mouse emergencies (such as unplanned litters, injuries, fighting, etc.). I can also assist with questions pertaining to orphaned mouse pups, weaning litters, and questions of mating and birthing. I cannot answer questions about exotic or wild varieties of mice such as spiny or pygmy mice. *****FOR EMERGENCIES, anything requiring immediate medical intervention, PLEASE take your mouse to a professional veterinarian or wildlife rehabilitator who works with mice as soon as possible! IMPORTANT RESOURCES: Raising Orphaned Mice: Orphaned Mice Videos: Natasha's Your First Mouse: General Mouse Help: Mouse Info and Exotic Breeds:


I have enjoyed the companionship of mice nonstop since 2004, and spent a year caring for them in a lab where I learned a great deal about their breeding, social needs, and health. I spent a few years breeding them, specifically working with albinos, marked mice, angora mice, and satins. My education never stopped - I am learning something new every day from current and well-established research thanks to the wonderful folks at the Jackson Laboratory, as well as from my wonderful mousey friends online. I also love learning from my terrific questioners here on AllExperts - you folks keep my passion for these amazing animals alive and well!

East Coast Mouse Association - expired, American Fancy Rat and Mouse Association - expired

Partial University for a B.S. in Microbiology, Partial University for a 2-year degree in Veterinary Technology (RVT cert), C.E. classes in pathogens, aseptic technique, genetics, and applications

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