Written by Anastasia Babbage from Too-Many-Mice
What I love about breeding mice is the ability to observe change and in a way evolution in real time. Mice breed quickly and over the generations their appearance can change quite dramatically.
When breeding pet and show lines, this is something the breeder needs to be aware of as many things not just looks can be genetic, temperament, susceptibility to illness and cancers as well as other traits are to a degree genetic.
But sometimes the breeder may be rewarded for their efforts in the form of a spontaneous mutation. Although, this can also be a curse as “new” genes are often unstable or come with unknown baggage attached in the form of health problems.
Due to the nature of sexual reproduction a mutation can happen at any time, in any group of breeding stock. Most of the time these mutations can be a advantage or even lethal. However, every once in a while, the pop up and wow us with their dramatic change from the norm.
I have found, from my own experiences and from research, that the best place to look for such a mutation is within well established, large population lines. As the animals will all be closely related the chance of a mutation being visible is much greater than in un related or newly established breeding lines.
This does pose its own set of challenges however as closely related animals are more likely to suffer inbreeding depressing, smaller size, reduced vigour and most notable the accumulation of undesirable traits things like thin short tails, small eyes, poorly formed years, and over all deformities. All the things a good breeder should be breeding away from.
In my time as a breeder, I have had a few of these spontaneous mutations occur. They have been both blessing and curse. In 2015 I had my first encounter with such a mutation, I was working a line of Siamese with the goal of darkest coats possible, my plan was to attempt to imitate the Siamese from the UK and USA without the extreme black gene, a gene we lack in Australia.
This blood line had been established for about 3 years originating from feeder stock where no new blood had been added to them in a while. I was quite bewildered to see one day that suddenly I had a small group of Absyssians. At first, I had no idea what they were and asked online for help identifying them.
Sure enough they were confirmed to be something new, suddenly everyone wanted to be my friend. The attention did put me off at first, but I still gave updates on them unfortunately in the end they turned out to be non-reproducible despite my best efforts. I had concluded that these were due to an unstable gene.
As can be the case with any spontaneous mutation. There can be many false starts and hiccups along the way to establishing new genes in any animal.
Unfortunately, I no longer have any animals from that original bloodline and the ones that did find their way into the hands of other breeders have been out=crossed to the point that the original line is lost.
Just recently a another “new” mutation has popped up in my lines, once again out of animals that originated as feeder stock, although this time I have added quite a lot of new blood from several breeders. This new mutation we are referring to as “Tri Colour” although it is still unproven. So far breeding trials for this line have seen mixed results with marked individuals popping up almost randomly and so far, no males have been produced only females.
I do hope to yield greater success with the “Tri Colours” than what I had seen in the past with the Absyssians. The line is still quite young and there is a lot of work to do with them yet.
As said above, a spontaneous mutation is not without its burdens and the breeder must be dedicated to working with them to repeat the results in a way refining one new gene is a lot more work than trying to create that perfect multi gene combo animal.
The effort involved can be well worth it as seen with the ever-popular patchwork mice, who had similar origins to the mutations I have detailed.
My advice for all breeders is to keep an open mind to the possibilities of mutations popping up. You might be the next lucky one to raise something never seen before in the fancy.