American Fancy Rat & Mouse Association

This article is from the WSSF 2012 AFRMA Rat & Mouse Tales news-magazine.

Breeding & Stuff

Kinked Tail Baby Mice; Mice Too Old To Have Babies; Deaf Mouse

By Karen Robbins

Kinked Tail Baby Mice

DaNita Crowl Brewer Delgado, Facebook
QI have been breeding mice for a few years and the last several litters from different moms have had one baby with a kink in the tail. At first I thought it was something the mom did, like squish it on the wheel or something, but now I realize it is genetic. Is this a bad trait? How do I get rid of it? Is it harmful to the baby?

Mouse with kinked tail

First 3 litters were all different moms, 2 of which were siblings but not littermates, the other mom was unrelated, had the same dad. Last litter is unrelated mom but son of first dad. If I had to weed out the moms and dad, I would lose 60% or more of my mice.

The first two moms have had litters before the kinked tail baby with no issues and same dad. I stopped using the moms, mainly because they were getting old. So I will need to get a new male and build up again with unrelated females. Currently I have the son and one of his sons, as males. The youngest one has not bred yet due to his age.

The sad part is that I was just starting to get the red color and broken pattern that I was looking for.

AI’ve had this come up occasionally but have never kept them past weaning so I don’t know how they do into adulthood as far as if it gets worse, or if the mouse has any problems with the tail.

There are several tweaked tail genes, most are semi-dominant. While some just affect the tail, some also affect the vertebrae and cause other physical problems. There are two genes I’ve heard of that produce curled tails like the one in your photo. One is recessive, Porcine Tail, that ranges from slight bends, to bends and loops, to a tightly coiled stump and can be waltzers. Genetic details on the Mouse Genome Informatics site. The other is semi-dominant, Loop Tail, that have looped or crooked tails with head wobbling to more severe problems. There is a 1949 article with photos of Loop Tail on the Journal of Heredity site and genetics details with a photo on the MGI site. In either case, they do have problems and their health would be an issue.

If the fathers of the litters with kinked tail babies are just the 2 males (father and son) and they have produced a kinked tail in every litter they have sired, then I would say it is coming from the dads and they shouldn’t be bred from. If these females are related to the fathers of their litters and if this is recessive, they would definitely be carrying the gene to produce it.

Yes, one of the frustrating parts of breeding animals—just when you are getting somewhere, then something comes along to change your plans. Don’t despair, I’ve gone through many similar frustrations, but having healthy animals is important. Who knows, this change may be for the better!

Mice Too Old To Have Babies

DaNita Crowl Brewer Delgado, Facebook
QI’m not sure what happened but yesterday my mouse moms killed all but 3 babies that were born 2 days prior, then sometime in the night they killed and ate them too. The mom’s were doing great after they were born. I wonder if my moms are too old (only 16 months old)? These 3 moms have been together for over a year and had beautiful litters. All the moms will be separated from my breeding stock and allowed to finish their lives as pets.

AYes, sounds like it’s their age. The ideal breeding age for mice is 3–8 months, sometimes a little longer, so 16 months is great grandmother age to be having kids. Letting them be pets is the best at their age.

Deaf Mouse

Shane Vogel, Facebook
QIs deafness in mice passed on through generations?? I never even noticed, nor was I told, that my buck was deaf until last night. He’s a PEW Frizzy, acts like all of my other mice, but I noticed last night when I dropped a metal object and all of my other mice jumped, he didn’t even turn his head to look, and it was closest to his cage.

He was bred to one of my does, and I’m worried about this litter now. Do you think his deafness will be passed onto his pups??

AYes, deafness can be genetic. It can also be a result of old age. Since pet mice have all their needs met, they don’t need to rely as much on hearing to survive in captivity (more in these articles Mouse Senses; Mouse Sensory System, Mouse With Head Tilt, Colored Mice). It depends on the cause of your male’s deafness as to whether his kids will be deaf. *

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Updated March 28, 2016