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New World Downunders
By Connie Perez

Introduction (April, 2003)
About three years ago, 2000 or so, I chanced upon the RMFE (Rat and Mouse Breeders for Excellence) website, and I noticed an unstandardized variety from Australia called ‘downunders’. The name made total sense since Australia is indeed known as the ‘Land Down Under’, and the little Aussie rats had the most amazing belly spotting (‘down under’) I have ever seen! For anyone who has any familiarity with rodent coat color pigment development, or mammal pigment development in general, it is one of those genes that ‘should not happen’. It is a dominant gene. Initial suspicion was that it was an allele of the hooded series, since the first downunders were discovered amongst hooded rats. But, recent conjecture now leans toward the idea that this is a totally separate gene that both modifies hooded alleles and interacts with hooded alleles. (The common hooded alleles include self [HH], Irish [hihi], hooded [hh], notched [hnhn], etc.)

Initial Inquiry
I made my initial inquiry with Tracey York of bRatpack and RatmanDu Ratteries in May of 2002. My initial inquiry was quite casual, since the thought of actually importing all the way from Australia literally seemed like an impossible dream. I was quit intrigued by the downunder gene, and Tracey was extremely helpful for questions. (I had lots of questions!) I had lucked out with my first contact, since of course most breeders do not ship because of the difficult work involved. Tracey already had much experience with shipments within Australia, and had even done the first international shipment to Holland.

Decision to Include Aussie Colors
For whatever reason, I had initially believed that the Australian colors were UK imports – made sense to me, since what would be the statistical odds that colors such as red-eyed dilution, mink or blue could possibly re-mutate independently from the rest of the world? So, when Tracey mentioned to me that Australia cannot allow imports since they are a rabies-free country, I really started to wonder if the Aussie red-eyed dilution, mink, and blue could be repeat mutations, or if they just might be unique new genes altogether… This led to the first shipment delay, since my request had gone from just the downunders themselves, to a request for the Aussie colors as well. My hope was to test the colors with what we now find in the United States.

Delays to the Shipment
Just blame the weather, I guess… Timing was highly critical to the entire shipment. The seasons between the Northern and Southern Hemispheres are pretty much exact opposites. While I was making my requests during our summer, Tracey was heading into the Aussie winter. So, some exceptional litters were born, but we were still hoping for inclusion of the Aussie mink and blue genes, and my last-minute request for the Aussie satin. Everything pretty much came together by November 2002. Tracey had about five litters born within a month of each other – that is one hefty undertaking – five litters to order! The timing of the litters was also critical because the shipment was charged by weight. Baby rats were expensive enough – I certainly did not wish to pay for importation of fully adult rats! Of course, the final concern was that we had to get these little ones over here before our own winter set in. (These guys left their Aussie summer, and were welcomed here by our California winter rains!)

What Finally Came Over
After all was said and done, I actually only brought over three downunders. My boys included: one argente hooded downunder (son of the first Aussie odd-eye), one black downunder, one black Berkshire, and one cinnamon carrying the Aussie blue. My girls included: one black downunder carrying the Aussie satin, one black cardigan carrying the Aussie satin, one blue agouti carrying the Aussie mink, one cinnamon hooded, one powder blue hooded, and one mink English Irish. The Aussie argente is their A_mmrr. The Aussie powder blue is their mmrr. (I mention this in hopes that folks over here will not confuse the American terms for ‘argente’ and ‘powder blue’ with the Australian terms.)

Shipment Preparations
I will be totally honest to say that this was my very first international shipment. As far as I know, this is the very first shipment ever between Australia and the United States. One of the first items to attend to was all legal requirements for entry into the United States, including veterinary certifications and USDA notifications. I was, and still am, naïve about the official rules – it took me about a month just to contact the correct USDA department, in order to learn the requirements for a shipment of this nature. I was quit surprised to learn that no quarantine was required from Australia to here – this is because Australia is still a rabies-free country. Everything boiled down to a veterinary inspection in Australia, and a USDA inspection upon arrival in the USA. (Of course, they don’t make it easy – I had to wait a few hours for the inspectors to show up – I probably had never paced so much in my life!)

Friday the 13th – Lucky Day
That Friday morning was a tad nervous for us over here, for Tracey, and for the ratties of course. As luck would have it, I awoke that morning with a fever, and looked out the window to one of our first big winter rains. I don’t drive, and the airport gets mighty expensive by taxi… But, just like giving birth, I knew it was the day – there was no sending ‘em back! Since this was my first international shipment, I initially went to baggage, in order to inquire about where exactly to pick up the babies. (The ratties had landed in Los Angeles, and transferred to United Airlines into San Francisco. I had such a fear that they would be stopped in Los Angeles, without me to intercede for them!) Long story short: to baggage, to cargo, to claims, to cargo, to claims, to cargo, home…

The First Days
OMG! I just could not believe the colors! I was not sure of my frame of reference – were the colors more like ‘rat’ colors, or ‘gerbil’ colors? (I have never raised hamsters, but perhaps the colors would be familiar to hamster breeders as well.) For sure, the mink looked like our mink, the cinnamon looked like our cinnamon, blacks looked like blacks, etc… But, the colors just seemed ‘different’ some how… Maybe more vibrant? Different, for sure. I was also very paranoid of them getting sick – it is not like we can do this kind of shipment any time we wish – these were very precious little critters! So, it was bland food like lab block and baby food and oatmeal for the first few weeks. I was so worried that they would get intestinal upset, from literally eating food they had never tasted before. As time passed, I did relax. But, I suspect I will remain on edge till we can get this gene out to interested breeders!

Rationale to Maintain Pure Aussie Lines
At this point in time, Australia is considered a megacolon-free country. There is much excellent online information regarding megacolon. This condition is often associated with spotting genes. A very simplistic explanation is that megacolon is a neurological disorder that affects the intestinal tract, such that the afflicted rat cannot defecate, and therefore will die without medical intervention. Even with intervention, death is the most common outcome for megacolon-afflicted rats – death usually occurs within a few weeks of weaning. By appearance, baby rats with megacolon appear ‘bloated’ about the belly, and yet often have very gaunt faces due to improper nutritional intake. It can be quite emotionally painful to watch such a baby die. Given such a somber picture, I hope it can be seen that I am looking forward to spotted lines of rats that will never suffer from megacolon. In addition, maintaining pure Aussie lines will mean that we can continue the fine work begun in Australia, with regards to colors and markings. One of my boys is the son of the very first Australian odd-eyed rat. So, I believe we may be witnessing the beginning of some new exciting gene combinations never before seen in this country.

Test of Aussie Mink
Since my girls were coming in younger than the boys, my first cross was my argente dowununder, Lil Nemi, with my American dumbo velveteen ‘self’ mink girl, AP Wagstaff (also carrying American blue and at least one eye dilution gene). There seem to be at least two genes in this country that resemble mink. I suspect that Wagstaff is the UK gene that is confirmed to be the true mink. The apparently American gene is sometimes referred to as ‘mock mink’, since the gene was sometimes seen in Russian blue lines that were exported to Europe. ‘Mock mink’ does not breed true with the UK mink. Out of Wagstaff’s litter of 12, 11 survived. All black or agouti – no minks or red-eyed dilutes. (I suspected Wagstaff of carrying red-eyed dilution, even though her blazed mother, RSCL Taffy, looks to be pink-eyed.) This litter result must count as one strike. I cannot state at this time, with certainty, whether Wagstaff carries the UK mink. I am a patient person, and so I know that I will eventually determine which ‘mink’ we had tested.

Test of Aussie Red-eyed Dilution
After the puzzle of Wagstaff’s litter, I felt that I should test the red-eyed dilution genes. I fully expected to see half of Wagstaff’s litter to be red-eyed dilutes. Over the years, I have come across much literature that supports the notion that new independent mutations of red-eyed dilution end up being confirmed as repeat mutations. That is to say, if a rat appears to be a red-eyed dilute, then it will be expected to breed true with any other rat that appears to be red-eyed dilute as well. (This is not always literally true – sometimes various gene combinations will result in a rat that appears to have ‘red’ or ‘ruby’ eyes, but the rat is not truly red-eyed dilute.) But, for this case, I knew that my Aussie argente only carried the gene for the Aussie red-eyed dilution. I knew that my American girl, OFR Waterfall, only carried the gene for our American red-eyed dilution. I was totally shocked, and unprepared to discover that the Australian red-eyed gene is distinct from our own American version. (This was confirmed by the observation that all of the 13 babies are black or agouti – we expected all fawn and beige.) This counts as strike two for the Aussie genes! I am not aware of any other circumstance in the world where this scenario has occurred. Perhaps this new Aussie gene will still be located on chromosome one, as are other dilute genes such as pink-eyed dilution and albinism? If not, then I will be totally baffled!

Test of Aussie Blue
I will cut to the chase – this was the only gene that we confirmed is identical to American and English blue. Just for general info, I will state that the blue rats currently seen in the fancy were discovered about 1990. As luck would have it, the gene mutated twice in about 1990, and was independently discovered in a UK pet shop at the same time as the gene was discovered in an American pet shop. I don’t know the UK history well, but I can say that the American discovery was made by local RMHF fancier Sylvia Butler, in her pet shop in Danville, CA. For my current cross, I bred my Aussie cinnamon boy, Donner (carrying Aussie blue) to my American blue dumbo girl, OFR Ashbury (carrying Siamese). Ashbury’s delivery lasted about four hours – the longest I had ever witnessed for a rat. She gave birth to at least 12 babies, but would not nurse or tend to any, till the last was delivered. I was frantically pacing for her. I was extremely tempted to foster the babies onto Waterfall, who gave birth to 13 babies in less than one hour, the very same day. With 13 babies, I did not see how I could add 12 to Waterfall! Thankfully, Ashbury began to care for her babies after the last was born. Eight survived. Of those eight, two are blue and one appears to be a blue agouti. So, it only takes one blue baby to confirm the genes are identical! (Since Donner was heterozygous for Aussie blue, not homozygous, we did not expect a full litter of blue babies.)

Recent Upset over Aussie Blue
Literally the same day that Waterfall and Ashbury delivered (March 4th, 2003), I chanced upon the Internet the recent concerns of the Aussie blue gene. The most notable expression is excessive bleeding, as during birthing or after a minor injury. Reports of deaths have been made for the Aussie blues from such. Other symptoms may include reduced fertility (male or female), smaller litters and excessive stillborn, possible depressed immune system, failure to thrive, etc. The symptoms have been compared to what is seen in von Willebrand disease (vWD) in humans. In humans, vWD is considered an autosomal dominant gene. For an affected human, this would mean that half of all offspring would be expected to inherit and express the gene. For our rats in question, I am not certain how a vWD-type disease would be inherited with the gene for blue (d), since blue in rats is an autosomal recessive gene. (That is, a rat must inherit two copies of the gene to be visibly blue.) I did a quick online search of the Rat Genome Database (RatMap) and found two references in rats, when I did a locus description query input of ‘von Willebrand disease‘. The query gave back the locus symbols [Mvwf] predicted at chromosome 10, and [Vwf] predicted at chromosome four. I happen to work for the UCB School of Public Health, and so I did a PubMed search for ‘rats and von Willebrand disease’. I got 21 hits, but I suspect many of those hits would not be relevant. But, at least it suggests that there *might* be rat models of vWD that have been studied in the past, and so that alone could shed light on the current situation now seen in the Aussie blues. As a final note on this (for now!), I will add that both the UK and USA early blues were seen to have similar concerns, though I cannot state whether the Aussie blues are more affected than the others. New theories are pending…

Early Concerns for Downunders
The downunders have only been around for a few years, since about 1999 or so. I am not familiar with the early history, but the early reports for some of the lines included eyeless conditions such as eyes of uneven size or one missing eye. The mode of transmission is not certain, but it appears that the tendency has been successfully bred out of the downunders. The eyeless condition seems to have been unknowingly exported to the UK (via Dutch imports of downunders from Australia – downunders were not directly imported into the UK from Australia). At this time, I am not aware of any new or recent cases of downunders with any eye concerns, and so I believe the American import is completely clear. I am not the best person to cover the early downunder history, but I am also under the impression that some of the early downunders may have had some personality problems. (I believe the very first downunder was a hairless male extracted from laboratory origins, and so that could be the reason the lines had variable temperaments.) In spite of these concerns, I am happy to say the imported rats have all been well tempered and just as people-oriented as any rats I have seen here. (Then again, the first hybrid litter born was just about the most active babies I have ever seen! Not skittish, but unbelievably active and inquisitive – never sitting still...)

General Characteristics of the Aussie Rats
Overall, the Australian rats have thus far proven to be generally smaller in size than what I have seen in the USA. I guess time will tell if the American palette for ‘super-sized’ rats will accept the smaller Australians as they are. Tracey York is a show judge, and I can definitely say her rats are very beautiful and sweet. Tracey has also done a wonderful job of breeding for colors. (To my mind, these qualities are more important than size.) I have noticed that the girls in particular really like to burrow into their bedding, especially when their cage is freshly cleaned. The mamas will totally bury their babies. These guys are tasters – they put everything into their mouths, and I have the nibbled shirts to prove it. They have thus far all proven to be people-oriented and quite mischievous. (One girl decided to camp out in our bathroom for a week!) Tracey has worked with some of her lines, such as her English Irish, for over eight years. She has worked on longevity – some of her rats have been known to live over four years. (I guess they need that extra energy, to keep ‘em going for four years!) Overall, I have found these charismatic rats to be wonderful fun and true delights.

Downunder Availability
The first hybrid litter is now out to four breeders, who are all online:

Cassandra Barlow (Romping Rats Rattery, Oregon):

Jennifer Flores (Li’l Rugrats, California):

Debbi Needham (Odd Fellows Rattery, Washington):

Sandy Sprague (Angel Paws Rattery, California):

We have covered all the Western states. The next set will probably be going to Missouri. My hope is that with wise planning, the downunders can reach all the major rat fancier groups within the next year or two. I guess just 47 states (and Canada) to go.

NWDUs Yahoo Group:
We have just started a new yahoo group, ‘New World Downunders’. I chose the ‘new world’ theme because in a sense, we are indeed entering unknown terrain. We have genes not seen in Australia, and so the potential for new gene combinations is unknown and full of promise – especially with the new possibilities for color combinations. I had also tried to think of a name that was inclusive of Canada, and possibly others in the Americas that may fancy rats. So far, this group has been quite enlightening with regards to questions and insights from around the world. The moderators are Cassandra Barlow and Debbi Needham. I am very happy that we are receiving strong support and advice from downunder breeders in other parts of the globe. I am also glad that there has been tolerance for tangent topics! (I see this gene as a possible ‘enhancement’ to varieties already existing here. So, downunders will not exist all by themselves – they will soon be dumbos, rexes, velvets, American colors, etc. Tangents just might spark inspiration for new combinations!)

Online Resources
There are many elements in this intro article that would be difficult for the typical rat fancier to locate. Plus, the updates have come in fast and furious. Therefore, I tried to list just a few online resources, to get interested folks on the road. This list is not all-inclusive by a long shot, and I know that there are many more excellent resources available online.

Aussie Blue Gene Alert:
Scamper’s Rattery:

Aussie Blue Rat Searchable Database:

Downunder Standards and Varieties:

AusRFS Qld:



Rat Fan Club:



Online Rat Database:
RatMap The Rat Genome Database:

Ratteries of Interest:
bRatpack Rattery / RatmanDU Rattery:

Milo Stud:

Mischief Makers Rattery:

Pendragon Rattery:

The Rats of Alpha Centauri:

von Willebrand Disease:

Hemophila Resources of America:

Yahoo Groups for Genetic Information:



This is the true history of the DU as public knowledge):

There is a marking pattern referred to as downunder that was imported to the United States from Australia in December of 2002. It is also available in Europe as it was sent there around the same time. It does not appear to be a white marking gene but rather a dominant gene that puts more color on the rat (not less). For instance, if the rat is hooded, addition of the downunder gene will also put marking similar to the dorsal stripe on a hooded rat on the rat's belly. They have been bred with selfs, berkshires, hooded, dalmatian and variegated rats with no health issues. Downunders do not have a tendency toward megacolon, and when they were brought to the US, it was with the understanding that US breeders were not to breed them to high-whites. A few have bred them to high-whites anyway, and they got the expected cases of megacolon. Kept out of high-white lines, they have remained megacolon-free. There have been no health issues related to the gene, and they can be bred together safely. The rat pictured at the left is a downunder from a downunder variegated father and a self mother.
Read the last sentence for that wikipedia article. That is where all the US DU tract to Look on NARR.
Originator of the breed and shipper of the 1st US imports (rich history found there):
History used to be in the OFR site but its down now....
Originated in Australia, imported to the United States in December of 2002 by Rat Genesis
Hooded, variegated or berkshire with markings on back and belly
Pictured rat is Australian mink-not US mink

RSA-provisional "Downunder Berkshire-The rat shall have a solid body color on top, with a colored belly stripe covering the white Berkshire belly, and be as symmetrical as possible. There should be as much white dappling and spotting as possible, extending up the sides from the white Berkshire belly edges and running full length between the front and rear legs on each side.

The belly stripe is to be a connected and continuous stripe of color, extending from the colored area beneath the throat all the way to, and filling the area between the back legs. The chest and belly should be completely colored. The demarcation between the white side markings and the belly color shall be as even, symmetrical and cleanly cut as possible. The colored belly should not contain any white spots. The back legs should have white socks to the ankle, and the front legs should have white socks to mid leg. The tail should have a white tip. The color is to conform to color standards, with Agouti based animals having paler belly stripes.

Faults: uneven belly markings and side markings; white markings on belly; color on feet, white chin or head spot; missing white tail tip, excepting in pink eye and ruby eye varieties.

Disqualifications: lack of belly stripe, white Berkshire belly not visible around belly stripe.

Downunder Hooded-The marking should include all of the head, throat and shoulders, and there should be a connected and continuous stripe of color extending from the colored area between the shoulders all the way to and including as much of the tail as possible. The stripe should measure 1 inch or slightly wider, and be in proportion to the rat, tapering slightly at the base of the tail to avoid coloring the back legs. The colored stripe should be complete, unbroken and run straight down the line of the spine without curves, being symmetrical on each side, and devoid of brindling or jagged edges. The back legs and feet are to be totally white. The front legs and feet are to be white to at least to mid leg, and preferably all the way to the body without disrupting the hood pigment over the shoulders. The belly stripe should be a connected and continuous stripe of color extending from the colored area beneath the throat all the way to and filling the area between the back legs. The chest and belly should be completely colored. The demarcation between white sides and belly color should be as even, symmetrical and cleanly cut as possible. The color should not extend up the sides and not contain any white spots. The sides are to be white and free of color spots, and the color is to conform to color standards, with Agouti based animals having paler belly stripes.

Faults: uneven, lopsided, narrow, broken or brindled stripe, uneven or brindled hood, color on legs, white marking on head, face or chin, colored spots elsewhere on the body or white spots on the stomach.

Disqualifications: no stripe down spine, no stripe down belly; obvious and conspicuous spots which detract from the appearance of the overall coat pattern.

Downunder Variegated-The back hood is to be as broken up as possible, giving the effect of spotting all over the back with side spotting. Sides are to be white with as many color spots as possible and be evenly distributed. The color should include all of the head, throat and shoulders with splashes of color over the back and sides. There should be a white spot or stripe on the forehead which is even, symmetrical, cleanly cut and not touching the eyes. The back legs and feet are to be totally white or white with colored spots. The front legs and feet are to be white to at least the mid leg, or white with colored spots, preferably all the way to the body without disrupting the hood pigment over the shoulders. The tail color is to be spotted. The belly stripe should be a connected and continuous stripe of color, extending from the colored area beneath the throat all the way to, and filling the area between the back legs. The chest and belly should be completely colored. The demarcation between white sides and belly color shall be as even, symmetrical and clean cut as possible except where intercepting a spot. The belly color should not extend up the sides and not contain any white spots. The sides are to be white with as many color spots as possible and be evenly distributed.

The color is to conform to the color standards, with agouti-based animals having paler belly stripes.

Faults: broken belly stripe; obvious back stripe, or back stripe not broken enough; back spots not evenly distributed from head to tail; missing color spots on tail; lack of headspot or stripe.

Disqualifications: lack of belly stripe; solid stripe down spine; broken belly stripe."