What is a Manx Rat?

Manx rats are tailless rats. This is a naturally occurring rat mutation and tailless rats have been documented as far back as 1915. The first documented tailless rat in the United States was produced by Karen Robbins in 1984. The variety was standardized by the American Fancy Rat & Mouse Association in 1993 (1).

For a while manx rats were actually very popular in Southern California. Unfortunately this meant that they were overbred and shipped off to pet stores that were unconcerned for the general health and welfare of the rats in question. This caused a major uptick in the number of unhealthy manx rats in the fancy and because of the health issues present in the overbred and pet shop rodent mill rats, very few breeders continued working with them and pet owners shied away from them (1).

Our original manx lines came from one of the few breeders who continued to work responsibly with the manx variety. As a result they are robust and healthy rats and our manx are part of a preservation line. Because the genes were clean and healthy when we received them, our goal is to preserve them while making improvements as needed in temperament. Our goal is for our entire rattery (both tailed and manx rats) to be completely free of genes that can cause harm to manx rats (whether they are purposefully produced or accidental).

​We absolutely do not sell our rats to pet stores and we don’t condone the mixing of manx with any kind of pet shop or rodent mill situation.

(1) See Tailless Rats: History - ​www.afrma.org/taillessrats.htm

How Does the Manx Gene Work?

Similar to dogs, different from dogs.

The manx gene in rats is similar to the C189G T gene mutation in dogs that is responsible for Australian Shepherds, corgis, jack russell terriers, and Australian cattle dogs. It differs in that it is a complex recessive gene rather than a heterozygous dominant gene.

What is a complex recessive gene?

A complex recessive gene is one that doesn't reliably appear at the normal 25% rate you would expect two carriers to produce it at. It takes at least three generations of manx bucks in the lineage to produce a manx pup. This suggests there are a series of genes and genetic modifiers involved that all need to align appropriately to produce visual manx. Modifiers for manx are responsible for the length of the residual tail. Some rats are genetically manx, but have full tails. Careful breeding will saturate breeding animals with clean and desirable modifiers whether they visually express as manx or not.

Working With Manx Lines

Breeding

We only breed fully tailed does to either tailed, or manx bucks. We don't breed manx does, as there are too many variables and individual potential complications. All of our manx does are adopted out as pets only.

Why we don't breed manx does

It's not possible to guarantee pelvis alignment and bone structure without a veterinary analysis and x-ray. Additionally, rats use their tails when giving birth, so the risk for complications in unassisted birth is higher than usual. Lastly, there is no reason to breed manx does. The highest number of manx pups we have ever seen in a litter was born at our rattery, where six manx babies were born to a fully tailed mother (see photo above). There is no significant increase in likelihood of producing manx offspring by using manx does, but it does pose an added risk to the mother.

Do we adopt out to other breeders?

Because manx is so tricky to work with, we don't typically adopt out breeding animals except very rarely to known experienced and established breeders that are able to responsibly manage any incorporated genetics. Even then we recommend they take a trio of our core manx line and breed those rats to establish the clean genetics in their rattery rather than introducing anything else.

Frequency of appearance

Typical visual manx presentation is approximately 10-20%, usually 1 in 10 pups per litter, if that, when breeding two established manx carriers together. We still don't understand what causes a higher percentage of manx pups to appear.  Whether manx is expressed visually appears to be random. The actual spinal length and tail nub length are not random. You can consistently produce cobby round bottomed manx in a well bred manx line with zero nub or noodle tail babies.

Tail docking

We neither perform nor condone any tail docking in rats that's not deemed medically necessary by a licensed veterinarian. Manx pinkies are sometimes born with tiny vestigial tails (see photo above). These tiny nubbins stay small while the rat grows and they either disappear beneath all of their fur, or are roughly the size of a grain of rice at adulthood. There's no need to remove them, and doing so can cause unnecessary nerve problems. 

Purpose

Manx rats are functionally immune to some of the most common types of rat injuries, tail degloving and pinch injuries. This means they are good candidates for homes with small children or differently abled adults who may have trouble ensuring that tails aren't pinched in doors or cage equipment, or who may not understand that picking up a rat by the tail can be harmful to the rat. They can also live more safely in environments with other pets where a tail hanging out of a cage can be a risk for the rat.

Additionally, manx rats are good candidates for people with sensory or phobia issues related to tails. Unfortunately this is one of the most common reasons why rats are shunned and sometimes harmed by people. Manx rats can serve as gateway ambassadors for those who might otherwise strongly dislike them.

Manx Rat Health

Balance

Rats born manx from healthy lines should not experience balance issues. Rats learn to balance within the first 1-3 weeks of life as they begin to crawl around the nest. Because they are born manx, they don't really have trouble climbing and playing like normal rats. The only exception is that manx pinkies sometimes get flipped over like turtles and may take a few extra rolls to right themselves before they build up the muscle strength to flip themselves as quickly as their siblings.  This should not result in any loss in condition, failure to nurse, or failure to thrive. If that is observed there is most likely a secondary health issue contributing.

Rats in general have incredibly good grip with their back feet. As a result there should not be any climbing or playing difficulties.

Heat Regulation

Unfortunately living in temperatures of 85F+ is problematic for all rats. It is best to treat husbandry of manx rats like that of guinea pigs and ensure that they're not in temperatures above 85F for extended periods of time. It's worth noting, however, that any temperature that would send a manx rat into medical distress or heat stroke would do the same to a tailed rat. Manx rats are less temperature sensitive than hairless rats, and in general it's best to house your rats in moderate temperatures.


Skeletal Structure

There is some confusion in the fancy because the manx gene in rats is very different from the manx gene in mice. Yet these two are often confused. The gene that produces manx in mice is random and produces tails of inconsistent length. This can cause spinal defects if the spine is too short. In contrast, the genes that produce manx in rats can consistently produce the same length. So a line of cobby manx will continue to produce cobby manx unless other genes are introduced or present in tailed individuals within the line. There's no major risk of skeletal abnormalities if the line is genetically clear of harmful modifiers and genes.

It is important to keep careful pedigrees to ensure problems can be immediately traced back to a source, should any problem arise. It's equally important to keep new lines separate from established manx lines, to prevent contamination from undesirable modifiers and genetic issues. Because the likelihood of producing manx is so low, it can be difficult to see a problem until you are several generations into breeding.

Where do unhealthy manx come from?

Most unhealthy manx are a result of people mixing new lines in with manx carriers. Establishing a colony of manx lineage rats can involve a lot of line breeding. Because of that, any undesirable recessive traits are likely to come to light. If new lines are used without knowing their exact medical background and compatibility you may find that there are undesirable conflicting genes in the mix. In many cases it can be things that also impact tailed babies equally. Manx is far from the only complex recessive gene present in rats and several others can cause medical complications. 

The "oops" manx

The majority of manx produced in the rat world are accidental. Because manx is a series of recessive genes and modifiers, and because it can be carried by tailed rats, you sometimes get a manx pup unexpectedly in a litter out of two random tailed parents. This is not the same as having manx baby born to a well bred manx line. It's the difference between an Australian shepherd naturally born without a tail and a tailless Labrador suddenly popping up in a litter. In one case the parents, grandparents, and great grandparents have all been vetted to ensure they produce healthy babies with good compatible bone structure. In the other case it's a fluke and may have unknown causes and unhealthy modifying genes.

We do not recommend breeding from oops manx. While some very experienced breeders may try to work outside traits into a manx line, you need to have a good understanding of genetics, established genetics tracking systems in place, and the ability to responsibly handle any resulting medical problems. This may mean ending lines 5 generations in when a problematic baby is finally born. 

This is why producing healthy rats with manx friendly genetics is the primary focus of our rattery. It's not because every rat is manx, or because manx is all we want to produce. It's because our goal is to have every single rat in our breeding program free of harmful modifiers and for any manx babies born in our rattery to be healthy happy babies regardless of their parents. This means we don't get to incorporate fun new traits that need work (like harley and werewolf), but it does make the rats born here as healthy as they can be.