# Is there such thing as a "dwarf mouse?"



## Lizzle (Apr 7, 2010)

I'm not talking about tiny Harvest mice or African Pygmies - I'm wondering if m. musculus domesticus (or even just m. musculus musculus) has been known, at any time, to have a dwarfism gene (or genes?). If they exist, would an individual mouse like this be healthy or have a lot of problems? I realize there is probably no real concrete answer here, but if anyone knows anything about this, please tell me?


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## Erica (Apr 18, 2010)

I have a mouse that was "off" as a baby. She didn't grow any fur until she was 5 weeks old, and now that she is 9 weeks old, she is still the size of a 5 week old (maybe a little bigger, but not much). I'm not expecting her to get much, if any, bigger. She will obviously never be bred, which is unfortunate, as she is my only LH self black. She is normal proportionately, and in all other ways, just tiny. She is such a little sweetie too. 

I can't say for sure that it is any kind of a gene, as she hasn't been bred, and won't be, so I don't know if she just wasn't taken care of properly my momma mouse, or if there is something different about her. She is my special girl, that's for sure. So far, she has had no health problems, but i do check her frequently to make sure she is warm enough, as I found her about a month ago, cold and not wanting to move alot. I held her in my hand for a bit, and warmed her up, then took her siblings out of the cage, and gave her a little alone time with momma mouse, but she hasn't had that problem since that time.


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## MyBoyKurtis (May 17, 2010)

There was a pup from my first litter that was half the size of the others, if not smaller. She wasnt smaller as a newborn, just never grew past a certain point. I miss her  She was such a friendly little thing


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## Jack Garcia (Oct 9, 2009)

Most individual mice who are very small but otherwise proportionate don't grow properly and have some sort of immune or internal developmental problems (like you've noticed, most don't breed).

However, there is a variety of dwarf rats so feasibly the mutation could occur in mice. I really wouldn't want my mice to suddenly pop up small though as they're bred to be larger and larger!


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## MyBoyKurtis (May 17, 2010)

Yes- my little girl didnt live very long at all.. only about a year


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## Cait (Oct 3, 2008)

There is a dwarf gene for mice, but only in labs as far as I know. Try Googling Yoda (a genetically engineered dwarf mouse who lived to over 4 years). In South America they also breed for small mice specifically, and have a special name for them. It begins with 'p' but I forget what it is.


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## Lizzle (Apr 7, 2010)

Thank you all for your input!

I know that show mice are meant to be bigger than regular fancy mice typically, but I would love to start a line of them that are actually smaller (but healthy) - sometime in the far off future. I'm going to look up this Yoda dwarf mousie just out of curiosity's sake. 

I have a mouse who never grew very big and is now an adult, but I just assumed she was a runt or had some kind of slowed growth due to some environmental factor. It appears that this happens a good amount of the time, though, based on what everyone is saying. I love my special little girly; she is extra sweet!


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## Cait (Oct 3, 2008)

I have remembered the name of the mini mice, it doesn't begin with 'p'. It's topolino.


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## Jack Garcia (Oct 9, 2009)

Cait, I had read about Yoda living for four years, but I never put 2 and 2 together and realize that he was dwarf!

It's so strange how smaller things generally live longer. In humans, females are smaller and generally live longer. A friend of mine who has a degree in some complicated sort of biology (I forget which) tells me that it's probably because the smaller you are, the fewer cells you have that can get "defects" (like cancer mutations) and kill you. All this is contingent upon being otherwise healthy, of course (and just naturally small). I'm nearly 6' and 250 pounds, so I guess I don't have long for this world. :lol:


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## moustress (Sep 25, 2009)

Isn't it also true that organs don't necessarily mirror the size of the frame, and that humans that are taller than average can suffer from cardiopulmonary insufficiency? I've wondered about this physiological aspect with respect to show meeces. In humans, the phenomenon can show up as things like collapsed lung, unstable blood pressure...now I have to go read about this again, cuz the details are a bit vague in my head.


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## Jack Garcia (Oct 9, 2009)

I'm not a biologist, but I think part of the reason humans are affected so is our upright posture. No other four-legged animal has fully abandoned its front two legs as walking tools (not even apes) and modified its spinal column to hold a mass of tissue and organs on just two legs the way that humans have. So even in mice, they still have more over-all support than humans do (even though they use their "hands" to eat and groom, as we all know).


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## Rhasputin (Feb 21, 2010)

I have a mouse, that was never a runt, but is hardly half the size of my other mice. I don't know of any health problems, and she's coming up on 9-10 months old about now. I'd love to think about breeding 'mini mice' but there are just so many risks involved. She could have pregnancy problems, she may have some underlying health problems that I've just never seen. Who knows. ):


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## Rhasputin (Feb 21, 2010)

Also, side note, I always thought the general rule was 'smaller animals tend to live shorter lives'
Or maybe it had something to do wtih metabolism...


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## SarahC (Oct 3, 2008)

I get a lot of mini mice from hairless.I don't know what the cause is.They are active and apparently well.Remind me of spiders.I've got one now.I'll try put a pic up of it.I've never tried to breed from any females and I leave the bucks running in with does but they never breed,presumably not strong enough to hold onto a doe.


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## nuedaimice (May 26, 2010)

I used to have a line that threw dwarf mice... I have a photo available of one of my dwarf mice next to a Show Mouse... The mice have a harder time keeping their own internal temperatures up, so may die if left in a large enclosure without many cage mates.

I had read up on Yoda years ago (as he has the same birthday as my father, 4/10, who is also a huge star wars fan), and I had done some more research when I realized I was getting dwarf mice out of my merle line.

If anyone is interested, I could post the photo of one of my dwarf mice?


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## Rhasputin (Feb 21, 2010)

Yes!


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## nuedaimice (May 26, 2010)

The dwarf mouse pictured here (a Satin Rex Piebald Merle) was older than the Satin PEW. She stopped growing at around 4 weeks of age, had a dome-y shaped head, was sterile, and had problems keeping her core temperature up, so we had special housing for her. She was a pet only. I took these photos as a size comparison.


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## Jack Garcia (Oct 9, 2009)

How did her siblings fare?


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## Rhasputin (Feb 21, 2010)

I think I have a mini mouse in my rex litter. He's doing fine though. 
He just stopped growing, and his brother and sister kept going!


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## nuedaimice (May 26, 2010)

Jack,

All of her siblings matured and mated normally. One of them was one of my nicest marked merles that I later bred to the buck photographed. This doe was just one of many that popped out of a particular line of merles. No other mice in my colony ever threw babies like this. They would mature normally until around 4 weeks of age and then stop growing. Most of them would die shortly after weaning because when I transferred them to larger community tanks they couldn't keep their temperature up. I started culling them when I realized what they were. Now remembering, they also had smaller eyes (and all had the domey shaped heads). This girl was only kept alive with special living arrangements to help keep her warm. She was a much beloved pet of ours, that I just couldn't bring myself to cull. I think she was around 8 months or so when this photograph was taken. She lived to be about 2 1/2.

The original line of merles was purchased from Crazzy H Rodentry, and I got a dwarf in the first litter off of those. It was a heavily line-bred strain, as well. I eventually, eradicated them with a few out crosses/breed backs. Although, I kind of wished I hadn't, thinking back on it now.


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## Rhasputin (Feb 21, 2010)

She looks just like my little texel that was at the show.


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## nuedaimice (May 26, 2010)

Yes, the RY I made mention might be a dwarf by his appearance. He had similar features from what I have seen in the past. I'm thinking that tiny little Fuzzy I got MAY be a dwarf as well. We'll see if he grows any (but I'm kind of hoping he DOESN'T!) He's so flipping adorable!


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## SarahC (Oct 3, 2008)




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## Cait (Oct 3, 2008)

Are they the same age? He really is as miniscule as you told me


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## SarahC (Oct 3, 2008)

no but both are fully grown.He is tiny but in good health and very very cute.I have repeated the mating that produced him which contains 3 bucks all of normal size.


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## Cait (Oct 3, 2008)

Without the broken for scale you would have assumed he was a normal size - he doesn't look like some of the 'dwarf' mice mice that people claim to have that are just runts or weak and sickly.


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## SarahC (Oct 3, 2008)

I don't imagine he has the actual condition of dwarfism.No way of knowing but appears to simply be a miniature mouse.I don't expect him to be strong enough to grip and mate a female either.I'm keeping him because he is a novelty.Just like your hamster :mrgreen:


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