Roofy when she was a tiny, rescued baby Roof Rat

The Domestication of Roof Rats (Rattus rattus)

How we got started

We were originally somewhat well known Norway rat breeders in Southern California. So, so when people found orphaned “baby rats”, they often brought them to us to rescue. At first we didn’t realize that these rats were an entirely different species than the domestic variety. But, when we did notice that they were different, it didn’t matter to us. They were babies that would otherwise die, so we did whatever we could to help them survive.

Many of them survived, and grew up to be healthy, active Roof Rats (known as Black rats in Europe.) Some were admittedly not very tame: indeed, the first one we rescued escaped as soon as her eyes opened and hid in our kitchen for months, eating holes in our melons and, finally, our new dishwasher until she was finally recaptured. Mostly, we were felt they were unacceptable as proper “pets” due to their skittish, willful personalities.

But there was one exception: Roofy.

Roofy the roof rat sitting in my hand

Roofy is the reason we are here

When Roofy was first brought to us, she was doing very poorly. She was a solitary rat, skinny and dehydrated, eyes close and just a bit of fur. Perhaps 10 days old. She had a few brushes with danger, such as a bloated belly and clicking when breathing, yet she survived and eventually thrived. A healthy, active Roof Rat. Yet, different. somehow.

Back then, before we knew the risk to their long tails, we used to let our Roof Rats run on large wheels. They are full of energy, and most loved doing it obsessively. They would fight each other for access to it. But not Roofy: she would remain apart from the others and quietly observe them. There seemed to be a calm intelligence about her that they didn’t posses.

Roofy actually seemed more interested in people than her fellow rats: when I opened the cage door she always rushed to come out and get a nut from us. She was the only one to do so.

She even learned her own name, and would come running back whenever we called her, no matter where she was in our two story home. So, we grew to trust her and allow her to explore and play outside her cage. She was very playful, craved human attention and seemed to truly love us. Intelligent, active and could do amazing physical stunts as befitted her arboreal nature.

We were still breeding Norway rats, but we never had a rat before quite like Roofy.

And we realized that, if we didn’t breed her, we may never have another. Sadly, rats don’t live forever, so the grim reality was that, someday, whatever she had that was special would otherwise die with her. I didn’t want that to happen. I was determined that Roofy would have progeny.

The first generations

So, we started breeding Roofy, and a few other somewhat manageable Roof Rats.

Our first generations weren’t always very good, and we still had to handle many of them in a tent. Fortunately, Roofy was always a very cooperative mommy rat.

But, surprisingly, we still have one of Roofy’s sons, Popeye. He’s about 4 years old, still healthy and we still breed him. He’s somewhat tame, and many of his offspring are very tame, indeed. Which they often passed on to their offspring.

Popeye has a pronounced, entirely depigmented tail tip which is genetic, and came from Roofy (she had a few white hairs there, and might have lost part of her tail tip before we got her.) Many of our most tame rats now have white tail tips that can be directly traced back to Popeye and Roofy. If they inherit it from both parents, it can often be quite large.

Agouti Roof Rat with White Tail Tip mutation
Agouti Roof Rat with normal tail
Black Roof Rat with White Tail Tip mutation
Black Roof Rat with Normal Tail

Agouti and Black Roof Rats with and without White Tail Marking

There does seem to be a slight correlation between lack of robustness and the extent of the depigmented area, but it is unknown which way the causal relationship goes: that is to say, does poor health of the mother or developing baby increase the the depigmented area, or does increased depigmented area lead to poorer health or hardiness? In Norway rats, there are some genetic diseases associated with excessive depigmented markings caused by inhibited migration of certain classes of cells in the developing fetus (as opposed to abinoism caused by inhibited production of melanin in cells that have otherwise migrated correctly.) It is entirely possible that white tail markings are correlated with other developmental issues, but I am not qualified to make that assessment on my own. But I can say that many rats with prominent tail markings are more placid than their unmarked siblings.

Popeye also has lighter colored patches on his face and body and, again, these are inheritable and many rats that have them tended to be more tame. Early on, I got a very good pair of siblings from a pairing of Popeye and his half sister, producing Flopsy and Peter Cottontail. Both of them had proment face markings and Peter had a prominent while tail tip as well. They were both exceptionally tame, learned their names and were essentially my pets. Sadly, Peter was never able to successfully mate with any female and we eventually gave him to someone with his cagemate as a pet. It turns out that many tame male Roof Rats are incapable of breeding for some reason, and this could be one reason why it was historically difficult to domesticate this species.

Peter Cottontail

Peter Cottontail with Author

Flopsy, on the other hand, was a championship breeder, and produced several fine litters for us.

I would say all of our rats are descended from Roofy, and most of them are related in some way to Popeye. Maybe half of our rats are descended from Flopsy. We have tried to balance preserving genetic diversity with producing tame rats, and this was the almost inevitable result. Flopsy was bred 4 times, then someone adopted her as a pet. She unfortunately passed away suddenly about a year ago from a respiratory illness at over 2 years of age. Roofy was also adopted by someone after 4 litters, and lived 2 years before dying suddenly from a stroke. It seems that male Roof rats often outlive females, but I’m not sure why.

Evolving husbandry methods

Although Flopsy and many others were very tame, we were still unsure if Roof Rat babies could be tame enough to manage. I had read and been told that the only way to reliably produce tame Roof Rats would be to take them from their mothers before their eyes were open and hand feed them until weaned. So, for a few generations, we did this, and produced many very friendly rats, like the Bandito brothers and Bao Bao. It was very labor intensive, and I hated doing it to the mothers and babies. And, besides, it made it hard to know for sure which rats were genetically tame and which were made tame by imprinting at a young age.

So, with some degree of apprehension, we entirely stopped that practice when we moved from California to Florida. Since then, all of our babies have been raised by their mothers in the normal way, and we intentionally do not disturb them until the babies’ eyes are open and they are running around. Indeed, we have less contact with our nursing mothers and their babies then we did with Norway rats, because some mama Roof Rats can get very nervous and even harm their babies if they are disturbed at a young age. This is something we have mostly bred out of them, and now most of our mama Roof Rats are happy the “share” their babies with us!

I’m happy to say that the transition to letting mama rats raise and socialize their babies until weaning went much better than expected. Our tame mothers did a much better job caring for their young than we could, and the babies were (mostly) still tame.

As expected, this allowed us to better identify the babies that were not truly genetically tame, so we could avoid breeding them.

At this point, essentially all of our rats are tame enough to be someone’s pet, and some are–dare I say it?–probably more tame than Roofy was. Especially taking into account that she was hand raised, unlike our current litters. Walter, for example, is literally the best pet rat I’ve ever had, regardless of species (more about him later.)

Florida brings diversity, some regression but a new color. And Walter!

Shortly after moving to Florida, we were contacted by someone that rescued baby Roof Rats out here. Up until then, we’d only had Roof Rats from California. She offered to give us some black, Florida Roof Rats to breed with our own, and hopefully have some black offspring. Unlike West Coast Roof Rats, which come from Asia, and are all Agouti, East Coast Roof Rats also come from Europe, which famously have black Roof Rats.

We soon discovered that Florida Roof Rats also tended to be bigger and, unfortunately, less tame and somewhat more aggressive. The first few generations of black Roof Rats weren’t very good. Nearly unmanageable and sometimes fought with and even injured our other rats. But, after several generations of careful selective breeding, some of our best rats are now black. The extra boldness and robustness, when tempered by the gentle, sweet nature of our existing line, led to some exceptionally brave, playful and lovable rats.

Walter, my current favorite, is a black rat. He is descendant from Flopsy, but perhaps 12% Florida genes. He free ranges every day, and is playful, fun-loving and very naughty and willful–but in the best possible way. He comes when he is called, no matter where he happens to be, and seeks people out just for play and companionship.

Yes, Walter gets into trouble all the time, including stealing my lunch and opening up packets of chocolates that he’s expert at finding (he does love his treats!) But when I catch him doing something wrong, a finger snap and “Walter!” immediately stops him in his tracks. He then usually comes running back to me to ask for forgiveness (did I mention he knows his name?) We are obviously trying to breed him but, sadly, many tame male Roof Rats are not good at producing offspring. Let’s hope Walter is the exception: if all Roof Rats were like him, I’ve no doubt they’d be highly sought after pets!

The Current State of Affairs

Currently, we have about 100 breedable adults. About 90% of them are homozygous Agouti, while the remainder are heterozygous Melanistic. As the Melanistic gene originated with untame rats, we have had to “wash” the Melanistic gene several times through our tame Agouti line, picking out the “best” black offspring from each litter. The hope was we could keep the gene associated with their black color, and hopefully, any other beneficial traits they might have, while “discarding” whatever combination of genes made them less tame than our existing rats I feel that we have been largely successful in this, as the general level of tameness is now similar in both colors. We have already been able to keep many Agouti offspring of Black rats for breeding, which we previously had no reason to do (as they were not tame.)

Perhaps 75% of our Agouti rats have light bellies. Maybe 50% have white tail tips. About 30% have two distinct shades of Agouti. Perhaps a quarter of the black rats also have white tail tips. Black belly color and shades are not as noticable, but no doubt they do carry the genes as it shows up in their Agouti offspring.

As for health, we have had them tested for Zoonotics and other diseases. They are mostly clean, but we know that they are carriers of Mycoplasma. Resistance to this bacteria seems to be genetically variable, as some of the lines descended from certain mothers have sneezing or other signs while others do not. Unfortunately, some of those lines also happen to be very tame, so it’s not a simple matter of not breeding them. Most of the lines descended from black, Florida rats are more resistant, so we hope that by breeding hybrid rats with good personalities and robust health, this will be less of a concern. Pity there aren’t better treatments or vaccines against Mycoplasma.

I feel that all of our rats are effectively pet quality, provided that one wants a Roof Rat as a pet and understands the differences between this species and Norway rats (which is a topic for a different article.) Generally, we recommend young pet Roof Rats for experienced pet owners that want a more exotic, “advanced” pet. They are a lot of fun, but high energy, physical and headstrong. Because they can go virtually anywhere, and are very curious, intelligent and adventurous, you do need to make their play area “rat safe.”

Rats don’t understand what human things are “for”, what they cost, why they cannot eat whatever they find (or at least try to) or why they are allowed to go some places but not others: this is true for all rats, but Roof Rats generally have a greater capacity for making a nuisance of themselves if given the opportunity. They are arboreal, so they are quick, nimble and much better at climbing and jumping than Norway rats. This is their nature: I doubt it can be bred out of them, and I’m not really going to try as that almost seems cruel. If you don’t want an arboreal rat, then get a Norway rat. They both make wonderful pets for the right owners, but if you adopt baby Roof Rats expecting them to be like the other rats you’ve owned, you will likely be disappointed.

That said, most of our adult Roof Rats, especially the older infertile males and former breeder females, are placid, lazy and well socialized by us. We often recommend that novices interested in Roof Rats start by adopting one of these rats rather than a baby. Even people that initially insist on getting babies will sometimes later exchange them for an older rat and be happier for it. Another option would be to adopt a young and older rat as a pair, as the older one will be the Alpha and teach the younger one how to behave. Mother and daughter pairs are especially good.

Recruiting more breeders, worldwide

At this point, all of our breedable rats are phenotypically “tame.” But they may be heterozygous in some of the many genetic factors that lead to tameness. Put simply, some behave more “tame” than others, and some of that behavior won’t always breed true. Even Walter, as much as I love him, can be a bit jumpy and “squirrely” at times. So, not every litter will be 100% “pet quality”, and only some of them will be worthy of breeding. Some seemingly good mothers or fathers won’t produce many “good” babies at all.

With every generation, the situation is improving, but some skill and patience is still required for breeding them. And because some personality traits only fully develop upon maturity, it is best to wait until the rats are at least 8 weeks old before deciding which to keep for breeding, and which to adopt out as pets.

Although we can fully advise new breeders about food, housing and other factors, breeding Roof Rats still requires more care and dedication than Norway rats. And you should be prepared to accept relatively more adopted rats back from people, because they are a more “advanced” pet and not as many people are familiar with them. We do have a active Facebook group of fellow Roof Rat owners (many of whom got them from us) which can be a support group for both breeders and pet owners.

If, after reading all of this, you are still interested in keeping them as pets, or breeding them: Welcome to the Family! We never charge for pet Roof Rats or for Breeding pairs. You can sign up for them on our Website, entirely free of charge and without obligation. We also welcome any inquiries and in person visits or video conferencing is available if you’d like to see the our rats and learn more about them. Shipping is available, both by van and air (unfortunately, we have no control over how much they charge for this.)

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