Dwarf Rats

Summary: Do you love your standard size rats but sometimes wish they could have stayed the size when you first got them? Enter the Dwarf Rat! Standard size rat personality and charm wrapped up in baby rat size. Coming in at about 1/3rd the size of a standard rat (with 1/3rd the amount of cleanup!!) Dwarf rats have also been seen to live slightly longer than their standard counterparts, due largely to the decreased size and lower observed instances of tumors/cancer.


The spontaneous dwarf rat was found in a laboratory colony of Sprague Dawley rats in 1977. It is a recessive mutation that causes them to have reduced Growth Hormone which causes them to be 40-75% smaller than their normal-sized counterparts, and in fact, a little larger than some fancy English mice. Most of our dwarf rats are the size of a 4-5 week old baby standard rat. Their size is a big part of why we don’t put them up for adoption until they are 7-8 weeks old; and they are about the size of a 3 week old standard rat. Fully grown, male and female dwarf rats weigh around 100 grams, while standard rats weigh between 250-450 grams (female) and 450-650 grams (male).

For the most part, dwarf rats look almost the same as standard rats, but there are a few ways to tell them apart. For instance, dwarf rats typically have bigger eyes in relation to their body, a shorter and thinner tail, and a different head shape. I like to think they have puppy dog eyes and it is adorable.

Size comparison of a full grown dwarf female to a standard female rat.


The temperament of dwarf rats is typically more playful and energetic. They still form strong bonds with their owners, love to play, and are very sociable animals that make great pets just like the standard rat. Usually there hyper playful energy cools down around 12-16 weeks old. Of course, just like standard rats, dwarf rats also have their own distinct personalities, so no two rats will be the same. It’s possible that your particular dwarf rat is very active, while another dwarf rat is more laid back and relaxed. But typically the male rats are more playful than the usual, lazy standard boy. Its almost like they keep there baby energy throughout their whole life. One of our first dwarf adopters explained the dwarf took a little longer to bond to her compared to her standards from us. But other adopters said the opposite how outgoing and curious they were. Very important to understand each rat has its own personalities.


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 they do not develop cancerous tumors as compared to standard rats due to reduced Growth Hormone. That is great news for those whom have experienced tumors in rats. This is one of the many benefits of dwarfs. With the lack of tumors, they typically live longer, since the typical rat passing is from tumors, respiratory issues or old age.


Dwarf rats still need the same housing requirements as a standard rat. You should still look to the rule of thumb that 2 cubic feet per rat is an appropriate cage size. A great resource for determine your cage size is correct for the amount of rats you have is “Rat Cage Calculator”. Make sure they have plenty of enrichments and space to run around, highly recommend a wheel. If your cage is tall don’t forget to add hammocks as fall breakers; this can help protect their fragile bodies if a fall does occur. Another great tip to add here from one of our fellow first dwarf adopters states how free roam time can be difficult. In her experience free roaming her rats in her whole room is how much more difficult it is to keep an eye on a dwarf. They can fit in many more hiding spots and tight areas which makes it so important to train your rats (like she did) or use a more confined area for play time. Extremely important to have the bar spacing of 1/2 an inch or cover the cage in chicken wire.

Introductions To Standards

This is an important step, you never want to just throw a dwarf rat in with your standard rats on day one (especially without even at least a couple of the steps). Just like introducing baby rats which are usually bigger than a baby dwarf rat to your mischief of exiting rats there is always the chance of conflict when establishing dominance. Introducing rats can be extremely stressful since exerting dominance can be as simple as over grooming or as rough as drawing blood. The rule of thumb in intros is no blood no foul, which means even they are wrestling and even be vocal but they need to work out them self in most instances. I have in depth blog article where i go in depth on different methods of introductions called the carrier method and things to look out for. But with dwarf rats this is even more important to ensure the small rats safety. Of course you must always be prepared that you might have to dominate of a rat to safely intergrade with your dwarfs. In this situation you can always safely return them to us or be prepared to house them separately.

During our year plus long experience and our adopters experience and stories we have some helpful tips to add to our basic introduction recommendations. We adopted out to 3 carefully chosen adopters who had adopted rat from us before, with lots of communication and learning. First of all introductions always do best in pairs so they have someone with their energy and size to play with and let out energy with, as well as take all the interest off of just one rat. Its also very important to take things slow and its okay to back track in steps to ensure the best experience for the rats integration. One of the best tips which one of the first adopters gave us was using toilet paper rolls/ paper towel rolls, this is extremely helpful as a safe place or hide that only the dwarf rats can fit in. I loved this suggestion so much i now use it as a staple in all my introductions with small rats to larger rats. You can even find PVC pipes to use as more permeant hides and tunnels for whatever size you need. Another dwarf adopter mentioned how vocal her dwarf is and loves to ride the backs of the big boys to make sure he grooms every inch of them, so adorable.


Our dwarf rats do cost more than our standard rats. The reasoning has a lot to with the size in litters and care. Dwarf rats typically have litter sizes of 2-5 babies, while a standard rats litters 6-14 babies. There fore its harder to keep up with supply and demand and breed ethically. We also house our dwarf rats separate for extra safety and able to make add enrichment specifically for them. Adding dwarf rats to our breeding room doubled the cages and cost of care, which as been amazing experience learning and testing for temperament and health and perfecting our line for the last year.

Published by Bob


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