Breeding ASFs

Breeding African Soft Furred Rats

Unfortunately, Metal Monkey Exotics no longer keeps or breeds ASF rats!

Praomys Natalensis – African Soft Furred Rats are quickly becoming a favorite as feeders for small to medium sized snakes, birds of prey, and carnivorous lizards and amphibians. Their small adult size compared to the Norway rat makes them ideal to keep, because they are often the perfect feeding size for months and will not outgrow the feeding limits for most carnivores like a Norway rat will.

They thrive in polygamous colonies, most often consisting of one male and three to five females. If you want to start breeding African Soft Furred rats, make sure these animals are not illegal to own in your state. (Link to small listing of US breeders)

They are a serious pest in most of sub-sahara Africa and it is economically the most detrimental rodent pest to crops and farming. Many states in the US found it appropriate to ban the ownership of these rats based on this and other facts associated with Praomys (Mastomys) Natalensis. This is most common in southern and western states of the US.

They are widely used in the scientific community to study diseases that are also common to man, like degenerative joint disease, renal disease and carcinoid tumors of the stomach.

The confusion with the names, as far as I can see, is outline from this article “Because of controversies many years ago, Mastomys was never phylogenetically classified as a genus, but remains a subgenus, designated Praomys (Mastomys) natalensis.” found here

Since they are still commonly referred to as Mastomys Natalensis, be sure to use both search terms when trying to find information about these animals.


Scientific Name: Praomys (Mastomys) Natalensis, (Mastomys Natalensis may be an outdated term)
Common Name: African Soft Furs, Natal Rats, Multimammate Rat, (Mice is an outdated term)
Average Lifespan: 2-3 years in captivity
Adult Weight: Males: 100- 130g; Females: 90-115g
Litter Size: 3-17;  average is 9-12 per litter. Will decrease with age.
Sexual Maturity: 54-63 days
Gestation: 21-23 days
First Litter: Approx 3.5 months of age. Will be bred again within hours of giving birth.
Menopause: Approx 12-15 mo. of age.
Note: African soft furs cannot reproduce with a rat or mouse.

Two litters piled in a bowl


Regardless of how many animals you need to feed weekly, I will recommend that most people start out with a group of one just weaned male and two females (1.2). This way you can learn the mannerisms of these rats, and see just how quickly they multiply.You can always hold back animals from this group to start others through line breeding, or inbreeding the siblings.

It is easiest to form a new breeding group when the animals are young, or when the females haven’t yet had litters. Once females have been bred and are in an established colony group, you cannot add any new animals without it being attacked and often times killed by the original animals. Even removing the male for just a day and trying to reintroduce him will result in the male being attacked and possibly killed by the females. I can’t stress it enough!

  1. Once a group is formed and bred, you cannot introduce any new animals without it being immediately attacked and possibly killed by the original members.
  2. Two unrelated males can fight to the death if left together in a group with a small number of females. Father and son, or fraternal relationships seem to not have the same intolerance.
  3. Never remove the male from the group and try to reintroduce him while the females have young. The females will kill him upon reintroduction.

Very few people have successfully fostered mice and other ASF’s to a group of nursing females. Be prepared for the loss of any fostered orphans.

Housing and Food

ASF’s should be given plenty of room to breed. For a group of 1.3, the smallest amount of space I personally give is approx the same floor space as a ten gallon tank, or a 56 qt plastic tub. I think this is roughly 17″ x 12″ square inches.  The hopper and water bottle is low enough to the ground to allow young pups to reach, but they do not have easy access to chew any of the top of the enclosure. (Link to DIY for tubs).

It is also possible to house ASF’s in a rack, however I do not have any first hand knowledge of extended periods housing them like this. If the group is given a wheel, I found that attaching it to the lid of the tub was beneficial in leaving more floor space for the young pups.

ASF’s do well fed a quality lab block. Common brands of feed for ASF’s include Harlan Teklad, Mazuri, LabDiet, Zeigler and Kent rodent feeds. many people have been using an unmedicated hog feed in their colonies. They also enjoy some seeds in their diet. Millet is a favorite of the species, along with black oil sunflower seeds. Corn tends to mold so is best avoided. Black striped sunflower seeds are incredibly high in fat and should be given sparingly.  They will also make use of fruits and vegetables, timothy hay, dog treats, and whole grain products, although the latter should be given as a simple treat and not a steadfast source of food.

Offering untreated wood blocks and paper products to gnaw and shred is favorable but not mandatory.


ASF’s are incredibly easy to breed. Simply by putting them together in a group, you don’t have to do anything other than provide good husbandry and remove the babies as they reach 4 weeks of age. There are a few important rules to be aware of.

  1. You will not be able to introduce any outside members to a colony once they have successfully bred and born a litter until well after the offspring have been removed.
  2. You CANNOT remove the male and reintroduce him to the colony while there are still young present. The females will attack to protect their young.
  3. ASF’s are incredibly protective of their young, keep this in mind when working with them, they are highly motivated to protect their young.

Introduce the new breeding group to each other. I find a 1.2 or 1.3 is a successful ratio, although groups with more females can work if given proper space.

Female ASF’s are sexually mature at approx 8-9 weeks of age. This does not mean that a female will get pregnant immediately and have her first litter at 12 weeks of age. Many times, females will not have their first litter until 3-4 months of age.

The pregnancy will last for approx 21 days. The female can give birth to as few as 4 pinks, or as many as 20+ her first time. After the female has given birth, she will go into heat a few hours later and will be impregnated again. This back to back breeding does not seem inherently detrimental to the female’s health or future litter sizes.

All the females in the group will nurse and care for the litters indiscriminately, and you will often see the older pups and the father helping to take care of the pups. The young will sit in one big pile in a corner with an adult spread eagle over the whole group.

Once the ASF are approx 4 weeks old, remove the young from the group and place them into a different cage/tub. By this time, the female that gave birth to the weaners will very likely already have given birth to her next litter, or will very soon and be HUGE.

Each female has a litter every 4-5 weeks, and if you have 2 or 3 females, that’s the very real possibility of having 32-54 rats born every 4-5 weeks, that need to be “grown up” for a little over a month just to reach a common feeding size.

The only hazard with having a female heavy group is the possibility that the older pups will push the pinks down to the bottom of the pile removing them from nutrition and subjecting them to possible suffocation or crushing.

All members of the group will be protective of the young. Sometimes they are intentionally aggressive, although this seems to wane as the group ages. They will nip you if you are not quick enough.

It will most likely be necessary to have seperate holding areas for the weaners. It takes a little over a month for them to grow to the traditional feeding size of 40-60 grams. They can be easily gassed with CO2, and frozen for later use. When feeding live, always monitor to make sure the animal is not harmed by the rat.

These pups are 4 weeks old and approx 20 grams


I’ve decided I should probably put in a little note about cleaning the ASF tubs when there are pinks and pups, I often forget that people are new to breeding rats when they read this page, so I should try to cover all aspects.

Can you clean an ASF cage when there are babies? Yes! Of course you can!  In my house, the ASF cleaning takes the longest, and here is the reason why, ASF hoppers bolt around the cage avoiding being caught by me. It’s cute, but takes a while to grab each rat even when you are grabbing two or three at a time to transport them to their clean tub.

Want to make this as hassle free as possible? Okay, ditch the gloves and pony up! Touch those rascals all over and get them used to your hand. It will make it easier down the road.

I always have an extra tub on hand, either a temporary tub to hold one of the groups while I clean, or a tub that is already made into a housing tub. Reason? It’s easier to just move rats once, than to move them all out of their soiled tub into the temporary tub, clean it, refill bedding, then move them all back into their new tub. That’s two times your moving the same group, and I always want to minimize stress on the breeding groups.

  • 1. Have an extra housing tub, place in bedding, fill food and water, and what ever extras you give your rats.
  • 2. Grab the dirty tub with the first group, place it as close as you can to the new clean tub.
  • 3. Gently grab the adults and place them in the new tub. I grab them by the base of the tail, unless the female is VERY large and ready to give birth, then she gets a ride in a scoop (scoop pic link). Just usher her into the scoop with a solid inanimate object like a block of wood or ruler. They usually are slow to move but don’t mind. Gently move her into the clean tub, and gently tilt up the bottom of the scoop until she slides out, slowly of course, no pregnant lady likes to be tossed around ;).
  • 4. Scoops are your best friend for the pinks, scoop those babies and put them in the bedding where the females usually place their nest. It’s also not a bad idea to leave some of the old shavings with the pinks, because they are very in tune to the smell of their surroundings. If they think they are in danger, they scramble everywhere! If you keep them all together with a pinch or two of the old bedding, they are more likely to stay put. You can usher in the hoppers and pups too, and it makes it easier instead of grabbing them all individually and moving them.
  • 5. Your done! Clean out that soiled tub, washing is always a superb idea for cleanliness, and repeat steps 1 – 4 with the rest.


Creating New Groups

You will likely find one day that your starting group is getting old, or is not producing the numbers you need. In this case, you could go out and buy some more rats, maintain quarantine for a period of 3 months…. OR, you could create a new group from the animals you already own.

Line breeding and inbreeding are two ways to expand the number of animals you work with. Line breeding is when the parent animal is bred back to its offspring. Inbreeding is when the siblings are bred to each other.

It’s my understaind, line breeding would be the smarter choice. This is because the parent will always have genes that its offspring does not have, since a parent gives one half of it’s genes, and the other parent gives the second half. Whereas siblings were made from the same parents, they both carry more of the same genes from both the mother and father alike.

Line breeding can be achieved in many ways.  If you just want to replace an aging rat from a group, leave a youngster of the same sex in with the colony, and remove the rat you want to replace.

If you want to create a new group of rats, you can take your adult male, and two or three of his daughters to start a new colony, while leaving a young male offspring in the original colony to take over his spot. Inbreeding can be done too, and may be easier in some cases. Take 3 young rats from the same litter and start a new group with them.

If you have more than one colony group, you can put weanling rats from these different groups together to mix up the gene pool and start a new colony. It’s all very easy to do.


Breaking Up Groups

So now you have a group that no longer needs to be producing for whatever reason, or you want to completely swap members. Age, disease, production issues; regardless the reason, it is sometimes necessary to break up groups and start over.

  1. Remove the male:
    This is the first step. Remove the male and place him in his own enclosure for a few nights, then it is usually safe to put him back in a general population tub with other males with minimal risk of fighting.
  2. Remove Females from “Nest”:
    Once the young are weaned from the final litter (1.5-2 months since removal of male), you can safely put the females into a general population tub. The act of removing the females from their “nest” and into a high density population usually (but not always) removes any intolerance or aggression issues.
  3. Create your new group:
    Once you have successfully integrated all of the female rats back into the general population for a few days, those same females can now be easily paired with a new male and other females.

Be cautious! I have been able to break up and create new groups this way, but please make sure you pay attention to the individual dynamics to ensure there is minimal stress and the best chance for reintroduction of new animals.

Humane Euthanasia for Rats

I am writing this small section to direct you to my Humane Euthanasia article that outlines the socially and humanely acceptable methods for euthanizing your rats. 

Humane Euthanasia for Rodents

I do not support other methods, I understand some commonly practiced methods may be approved by the AVMA, but only for qualified and supervised professionals in a controlled environment.  I feel that the margin of error is too large to promote with good conscience regardless of the condoning by the AVMA.

Feeders or not, they deserve respect. Without them, you would not be able to keep your snake.

Final Thoughts

African soft furred rats are an easy species to breed, with many benefits for breeders. What they lack in tolerance for humans, they make up for in high production rate and large litter size.

The down side to raising ASF’s is they take at least month and half (45-60 days) to grow up to feeding size (40-60 grams). This means you’re raising a LOT of rats, and the majority of your tubs will be holding tubs.

They eat just as much as a domestic rat the same size, and also have the incredible ability to chew out of enclosures if not made secure enough or given enough space.

I recommend these rats to anyone that doesn’t have the space or time to devote for large Norway rats, but still wants a steady supply of feeder animals they can depend on. They make excellent feeder animals, where the few limitations are outweighed by the benefits in regards to space, odor, and production reliability.

We’ve put a lot of work into each piece, and want to remind everyone that if you like what we do here, please make a link back to this page, rather than infringing on copyrights.

We wouldn’t steal your works, please don’t take ours. Thanks for understanding! 

     avatar  :: Connie



Informational Sources Used

ASF Caresheet –

ASF Care

Sapphire Tigress (No longer available)

African Soft-furred Information and Exchange (No longer available)

If you would like to find ASF’s near your area, this webpage has a small current listing of ASF breeders. (No longer available)

If you are looking for ASF breeders in your state, follow this link. (No longer available)

Or you can visit the ASF’s breeders and information exchange forum  (No longer available)

Russell Toft’s Article on ASF’s (A good read, although may be outdated.)

Thames Valley Rodents (a small listing of personal blogs, a great source of technical information)

Ken-ichi Mafune, Kaiyo Takubo
The diversity of gastric carcinoma…snum=9#PPA4,M1

Tan C H; Tachezy R; Van Ranst M; Chan S Y; Bernard H U; Burk R D
The Mastomys natalensis papillomavirus: nucleotide sequence, genome organization, and phylogenetic relationship of a rodent papillomavirus involved in tumorigenesis of cutaneous epithelia…nship_of_a_rod

Rudolph R, Müller H
Induction of epidermal tumor growth in the skin of Mastomys natalensis by transfer of virus-containing tumor tissue from a squamous cell carcinoma
Zentralbl Veterinarmed B. 1976 Mar;23(2):143-50. German. No abstract available.

Mastomys natalensis  Papilloma Virus  (MnPV), the Causative Agent  of Epithelial Proliferations: Characterization of  the Virus Particle

K. Wayss, E. Amtmann, G. Fürstenberger, G. Sauer and M. Volm
Tumorpromoter modulate skin tumorgenesis induced by papillomavirus in mastomys natalensis…2&size=largest

J. Nafz, M. Ohnesorge, E. Stockfleth, F. Rösl and I. Nindl
Imiquimod treatment of papilloma virus and DMBA /TPA-induced cutaneous skin cancer in Mastomys coucha: an unique animal model system useful for preclinical studies…84058/abstract

Manfred Reinacher, Hermann Müller, Wolfgang Thiel and Roland L. Rudolph
Localization of papillomavirus and virus-specific antigens in the skin of tumor-bearing Mastomys natalensis (GRA Giessen)…195628!8091!-1

Julia Nafz, Anja Köhler, Myriam Ohnesorge, Ingo Nindl, Eggert Stockfleth and Frank Rösl
Persistence of Mastomys natalensis papillomavirus in multiple organs identifies novel targets for infection

Iris Helfrich, Min Chen, Rainer Schmidt, Gerhard Fürstenberger, Annette Kopp-Schneider, David Trick, Hermann-Josef Gröne, Harald zur Hausen, and Frank Rösl
Increased Incidence of Squamous Cell Carcinomas in Mastomys natalensis Papillomavirus E6 Transgenic Mice during Two-Stage Skin Carcinogenesis

Robert K. Jackson (have to scroll down to Mastomys)
Unusual Laboratory Rodent Species: Research Uses, Care, and Associated Biohazards…1Unusual.shtml

Klaus Wayss, Denis Reyes-Mayes and Manfred Volm
Chemical carcinogenesis by the two-stage protocol in the skin of Mastomys natalensis (Muridae) using topical initiation with 7,12-dimethylbenz(a)anthracene and topical promotion with 12-0-tetradecanoylphorbol-13-acetate

Anton J. Bilchika, Ola Nilssona,  Irvin M. Modlin, Karl A. Zuckera and Thomas E. Adrian
Significance of gastric endocrine tumor and age-related gut peptide alterations in Mastomys…f533d0be858763

J. D. Randeria
Animal model: carcinoids and adenocarcinoma of the glandular stomach of Praomys (Mastomys) natalensis.…?artid=2042366

Keniti KOZIMA, Takeshi MUROHASHI, Jun SOGA and Kenji TAZAWA

K. C. Snell, H. L. Stewart
Spontaneous diseases in a closed colony of Praomys (Mastomys) natalensis

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A blog about the breeding and keeping of snakes and rodents.