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Variety: Dwarfs!


Description: Dwarfs are NOT just small rats. ​You do not just get Dwarfs by breeding together two small rats & continuing to choose the smallest to breed. 


Dwarf is caused by the dwarf gene which is recessive. (*a recessive gene is when a gene needs to copies, one from each parent to be expressed. It can be carried and not show). This causes reduced growth hormone. This means they are about 1/3 the size of standard rats. This is quite a substantial difference!


Standard females weigh around 250-450g; standard males weigh around 450-650g on average.
Both male and female dwarfs are around 80-125g fully grown. Around 100g is normal.

Besides weight, there are some physical differences in Dwarfs vs Standards. They have larger eyes, thinner tails, a shorter rump & smaller feet.

Dwarfs can come in any color/marking/coat/ear type variety. 

It can be quite common for people to go "oh look this rat is small it must be a dwarf", that does not make it a dwarf. It is also important to note that some breeders or people try to sell small rats as dwarf and often these smaller rats are runts and/or have health issues. They can have stunted growth, developmental issues with their organs, heart, lungs not being fully developed. And also prone to more health issues, a weaker immune system and shorter lifespan. These are NOT issues in actual dwarfs. It is very important to buy from a responsible breeder. Ask them about their lines, how long they have been breeding dwarfs, where they got their lines from, how much they know about dwarfs, who the dwarfs parents were- the dwarf gene has to come from both parents so either the parents both had to be dwarf or carry dwarf.


Standard:  Dwarfs are currently not standardized by AFRMA. 



Excerpt: ‘Dwarf Rats’ by Debbi J. Neeham, 2005
The spontaneous dwarf rat (SDR) was found in a laboratory colony of Sprague Dawley rats in 1977. It is a recessive mutation that causes them to have reduced GH or Growth Hormone which causes them to be up 40-75% smaller than their normal-sized counterparts, and in fact, a little larger than some fancy English mice. Dwarf rats have been found to be resistant to some cancers, as scientists have studied the effect of chemically induced cancer on dwarf rats and found dwarfs do not develop cancerous tumors like typically sized rats due to their lack of Growth Hormone. That is great news for those whom keep rats in the rat fancy!

- borrowed from Rainbow Rattery


My dwarf boy Castiel at 4 months old (left)

My standard boy Banner at 6 weeks old (right)

12 week old dwarf Rey meeting 10 day old standard babies (not related)

Are there any differences in Dwarf personality or temperament?

No! There are no differences based on being dwarf alone. All temperament is dependent on their breeding & the line they are from. So if they come from a line with good temperament they will have good temperament, but if the line has issues ofcourse then so will they.

Always buy from a good responsible breeder. All newer varieties can have issues where greedy breeders rush to be the first with them and so they breed carelessly and sell early. This can mean some lines have many issues with health or temperament. Look for breeders who are responsible and have established lines.

My dwarfs are from beautiful lines and are the sweetest little angels! I admit dwarfs are about my absolute favorite things. So far all of my dwarfs are just amazing in temperament. So friendly. I often have my most favorite heart rats be dwarf. My sweet dwarf Ambrose is adorable and thinks he needs to be held everytime he sees me. That is often my dwarf personality.

Personality wise, dwarfs can be more energetic in a way. I remember once my nephew told me I should have named one Flash because of how he just zoomed around so fast! Some dwarfs when young can be a bit quick. They do not seem to realize their size or let it stand in the way. At the same time, other dwarfs can be quite lazy as well, more so as they age. 

The health of Dwarfs?

For some reason, there is a common misconception that Dwarfs are somehow unhealthy. This is not true. There are no health related issues from them being dwarfs or caused by the dwarf gene.   Dwarf in rats is NOT the same as dwarf in other animals, like rabbits. The dwarf gene is not a health issue, it is just caused by a reduced growth hormone.

Some lines may have health issues; it is the same with temperament. It all depends on the line & the breeding. If it comes from a line with health issues it will, in turn, have health issues.

None of this is caused by being a dwarf though.

A word of caution: some ignorant or unethical breeders may attempt to sell “small” rats as Dwarfs. I have actually seen people scammed by this before. Quite often these small rats are sickly rats that have stunted growth and health issues. They are not healthy thriving animals. They are also not Dwarfs. Dwarfs are a newer variety they are very unlikely to be found in pet stores or randomly out there. As it is a recessive gene it is also very uncommon to just show up in a litter as it would need to be from both parents. Every so often I see people claiming their runt is a dwarf because it is small or worse a FTT (failure to thrive) baby is a dwarf. Please be cautious.

As mentioned above they do have less risk of tumors, which for anyone who has dealt with tumors in their rats know the beauty of that! -

Dwarfs have the same lifespan as standard rats.

You do need to be careful of their diet and weight. They are very little & so even small portions can tip the scale in a big way! 

Some dwarfs have weight issues.

Housing and care of Dwarfs

Dwarfs are VERY small. Rat proofing skills need to be much more precise and you need to be very careful about letting them run around. I recommend a playpen over free range. It could be so easy to misplace one. One needs to be more cautious with Dwarfs. I do not really suggest them for young children. They will not handle small falls or rough handling as well as a standard rat.

Also a word of caution if you have other pets, cats/dogs may ignore a larger rat or even be afraid but they may be less standoffish towards the smaller Dwarf rat. It is also much easier for the Dwarf to be injured by them, even accidentally.

By far most agree that housing of dwarfs should be similar to that of standard rats. As I mentioned above they can be little zoomie jumpers. They need the extra room. They should NEVER be kept in crittertrail or small “hamster” style cages. They should still never be kept in tanks. I do think proper well ventilated bin cages are ok – 105qt+, wire mesh sides.

I prefer martin cages for dwarfs and highly recommend them. With the smaller squared bar spacing they are ideal. Critternations are still fine with the ½” bar spacing. The style of bar spacing does matter but never keep them in anything above ½”. I have dwarfs in a DCN. Word of warning the bar spacing on the very bottom level under the pan of a DCN is larger than ½”, Dwarfs can slip out of this if they chew the pan or get under it.

Toys, baskets, hammocks, etc… all need extra care so that small openings are not going to get anyone stuck. Be careful for shower hooks.


Can Dwarfs live with Standards?

There is not a simple yes/no to this. It depends on the personality/temperament of all rats involved.

All of my Dwarfs do live with standards, both my males & females. All of my baby Dwarfs will likely have lived and been around standard rats before ever being sold as well.

I know my rats very well. My rats are bred for beautiful calm temperament and no hormonal issues. My rats are not going to fight or attack one another. All of my rats, males & females, get to be around babies and I trust them to be careful and not injure the Dwarfs.

But I have sadly heard horror stories from people who had Dwarfs with standards and things ending very badly. I have even heard of horror stories of standards hurting other standards very badly or even killing. Some rats do not have good temperaments or have hormonal issues and there is a potential risk. If you have a 600g hormonally aggressive rat vs a 100g Dwarf… that is a scary size difference.

While I am confident with my rats it is because I know their history & temperament and I know from experience how they react to new rats and smaller rats. You must be honest with yourself. If your rat has never met new rats before you will want to be cautious because you do not know how it will react. If your rat has ever shown aggression or hinted at aggression type behaviors, I suggest you do not risk it.


My recommendation is that Dwarfs be sold with other Dwarfs and live with other Dwarfs only.
Start a new Dwarf only mischief! Setting up a second cage or if you are tight on space, I am perfectly fine with proper bin cages being used and can show you how to make one!

I feel if you want both together it would be better to add a baby standard to the dwarfs so it can grow up with them, rather than adding them to a standard.
I am more comfortable with females being kept together over males.

I only sell rats in pairs; I am willing to sell Dwarf + Standard in many cases.
I am also willing to discuss this with you and sell Dwarfs to live with standards as long as you are willing to use proper introduction techniques and take things cautiously slow, and that you have a backup cage and are willing to keep them separate if there is any hint at potential risk.

The start of my lines:


I got my first dwarf in early 2016 from Great Star Rattery. He was a marked Siamese named Castiel. And was the most amazing boy ever. Seriously he was the standard that I hold all rats to. 

Later that year I also got another dwarf from them a Black Blazed named Crowley. 

At that same time I also received two female dwarf carriers from the breeder HTGZ in Illinois. They were a Mink Harley named Esme and a Black Self named Widow.



My Lines- 

Dwarfs have much smaller litters, generally 3-5. This does mean fewer babies will be available. I almost always pair multiple litters at once so I will often have more available but nature has to cooperate. I can’t guess what genders I will get! Remember every litter I have is for my set goals of the line. I never breed for demand. So I will almost always be keeping back some for myself to better the lines.

Many of my lines do carry dwarf and as it is recessive it means dwarfs can potentially pop up in litters. 

But the lines I specifically breed for Dwarf are:

Dumbo Seal Point Siamese

This is my main line and my longest line that was outcrossed with the Dwarf Siamese GSR Castiel.

Dumbo Marten Variegated Blaze

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