| Dwarf Rats |
| My Comparison Pictures: |
| Bjorn (Standard) at 5 months old Bonsai (Dwarf) at 4 months old |
| Bjorn (Standard) at 5 months old Logan (Dwarf) at 4 months old |
| Vertigo (Standard) at 3 months old Touch Too Much (Dwarf) at 8 months old |
What are Dwarf Rats?
Dwarf rats are simply rats that are genetically smaller than Standard rats. They were first found in a lab
strain of Sprague-Dawley rats in 1977, and were referred to as Spontaneous Dwarf Rats (SDR). Dwarf
rats are the product of a genetic mutation that inhibits growth hormones, which results in rats that are
1/2-1/3 the size of Standard rats. Most Dwarves stay about the size of a 6-8 week old Standard rat their
entire lives.
Not only does this make them smaller in size, but according to numerous studies, Dwarf rats are more
resistant to many forms of cancer and are at a reduced risk of kidney disease than Standard rats. This is
also believed to lengthen the Dwarf rat's lifespan.
All positive, right? Well, there are also studies suggesting that there is a trade off for these benefits.
Dwarf rats may be at higher risk for cartilage degeneration, as well as impaired memory and learning
abilities. What does this mean for Dwarf rat breeders and owners? These problems are still being
researched as to what impact this will have on the Dwarf rat as far as breeders and owners are concerned.
strain of Sprague-Dawley rats in 1977, and were referred to as Spontaneous Dwarf Rats (SDR). Dwarf
rats are the product of a genetic mutation that inhibits growth hormones, which results in rats that are
1/2-1/3 the size of Standard rats. Most Dwarves stay about the size of a 6-8 week old Standard rat their
entire lives.
Not only does this make them smaller in size, but according to numerous studies, Dwarf rats are more
resistant to many forms of cancer and are at a reduced risk of kidney disease than Standard rats. This is
also believed to lengthen the Dwarf rat's lifespan.
All positive, right? Well, there are also studies suggesting that there is a trade off for these benefits.
Dwarf rats may be at higher risk for cartilage degeneration, as well as impaired memory and learning
abilities. What does this mean for Dwarf rat breeders and owners? These problems are still being
researched as to what impact this will have on the Dwarf rat as far as breeders and owners are concerned.
| My goal with this page is to provide an overview of the Dwarf Rat variety. I intend to include all information I can, and make this page as complete as possible. |
How do they compare to Standard rats?
Dwarf rats are very much like Standard rats in many ways, but this was not always true. Dwarf rats now
have very similar temperaments to Standard rats, thanks to breeders working to improve them. They are
not the hyper, skittish Dwarves that first came into breeders' hands - now they range from very calm to a
bit exciteable - mostly depending on their individual personalities. Dwarf rats do tend to be a bit more
active overall than Standard rats, and this is especially true when comparing Standard and Dwarf males.
Conformation is another matter - some Dwarves still have that characteristic "dwarf look" - eyes and
ears that are larger and out of porportion with the rest of their body. There are also "stocky" Dwarves,
which look exactly like Standard rats in miniature. Most Dwarf rats have shorter legs and tails that are in
porportion to their bodies.
have very similar temperaments to Standard rats, thanks to breeders working to improve them. They are
not the hyper, skittish Dwarves that first came into breeders' hands - now they range from very calm to a
bit exciteable - mostly depending on their individual personalities. Dwarf rats do tend to be a bit more
active overall than Standard rats, and this is especially true when comparing Standard and Dwarf males.
Conformation is another matter - some Dwarves still have that characteristic "dwarf look" - eyes and
ears that are larger and out of porportion with the rest of their body. There are also "stocky" Dwarves,
which look exactly like Standard rats in miniature. Most Dwarf rats have shorter legs and tails that are in
porportion to their bodies.
| Comparison Pictures submitted by others: |
| (picture submitted by Veronica) Siamese Dwarf (Ari) at 6 months old on top of a 12oz can |
| (picture submitted by Meghan of Paper Heart Rattery) Wheaten Burmese Dwarf (Cricket) and Sable Burmese Standard (Hershey) both at 6-7 months old |
The genetic mutation that causes Dwarfism in rats acts as a simple recessive, so it is fairly easy to
reproduce. Here are a few hypothetical breedings that show how this works:
~ A Dwarf rat bred to a Dwarf rat will produce a litter of 100% Dwarves
~ A Dwarf rat bred to a Standard rat who carries Dwarf will produce a litter of 50% Standards and 50%
Dwarf rats. All Standards will carry the Dwarf gene.
~ A Standard rat who carries Dwarf bred to a Standard rat who carries Dwarf will produce a litter of
75% Standards and 25% Dwarves. 50% of the Standards will carry Dwarf.
It is important to note that Dwarf rats normally produce smaller litters than Standards. The average litter
size for Standard rats range between 8-12 pups, while Dwarf litters usually range between 3-6 pups.
Breedings between a Standard and Dwarf rat normally fall in between the two averages, and breedings
between two Dwarf rats are normally on the smaller side of the average Dwarf litter range.
reproduce. Here are a few hypothetical breedings that show how this works:
~ A Dwarf rat bred to a Dwarf rat will produce a litter of 100% Dwarves
~ A Dwarf rat bred to a Standard rat who carries Dwarf will produce a litter of 50% Standards and 50%
Dwarf rats. All Standards will carry the Dwarf gene.
~ A Standard rat who carries Dwarf bred to a Standard rat who carries Dwarf will produce a litter of
75% Standards and 25% Dwarves. 50% of the Standards will carry Dwarf.
It is important to note that Dwarf rats normally produce smaller litters than Standards. The average litter
size for Standard rats range between 8-12 pups, while Dwarf litters usually range between 3-6 pups.
Breedings between a Standard and Dwarf rat normally fall in between the two averages, and breedings
between two Dwarf rats are normally on the smaller side of the average Dwarf litter range.
How are they reproduced?