The dwarf rat was first discovered in 1977 in a laboratory in California. My dwarf line comes from Ohio. I bought my first dwarfs in 2015. I purchased from a couple of sources, however only continued to use 2 of them in todays generations. A black recessive blazed velveteen male and a russian blue female, both from Ohio.
I crossed them into my standard sized bloodlines, which consisted of various varieties including, silvermane, harley/long haired, marble, downunder and others. This is where my babies of today originated from.
Dwarfs are not deformed in any way, they are simply just a smaller version of normal standard sized rats. They are smaller due to a lack of growth hormone. This lack of hormone has also lessened the chances of various cancers, and slows down tumor growth.
Dwarfs are often used in laboratories in cancer research for this very reason. It is believed that dwarf rats have a slightly longer life span, however they haven’t been in the pet community overly long yet, so it’s still not 100 percent proven.
Dwarfs are much easier to keep as pets, as there is far less odor, to none. Cages always look clean and you will never find saturated corners. I myself have horrible allergies to standard sized rats, especially males and find that my allergies are not bothered at all by dwarfs. This is one of the main reasons I only keep dwarfs today.
Dwarfs are typically 1/3 the size of standard sized rats. However the genetics for size behind the standard rats in the pedigrees will influence the size of the dwarfs. Most of my standard sized rats were on the large to extra large side. Most of my dwarfs are medium sized for dwarfs, some and smaller and some larger and very heavy boned.