I am often asked which hamster pairings should be avoided. This article is an attempt to list the ones I know of. This will be a living document, and I will add to it as I become aware of additional pairings to avoid.
Physical Defects
There is one gene in the Campbells and one in the Syrians which will cause babies with physical defects. Both problem situations are very predictable and follow traditional genetic principles of inheritance. The Campbells gene is the Ruby-eyed Mottled Gene (Mi). The Syrian gene is the Anopthalmic or Roan/White Bellied gene (Wh). Each of these genes is a wonderful gene and produces beautiful babies when bred responsibly. When bred irresponsibly, though, deaths or physical deformities will arise. (Note: Each time the term “mottled” is used in this article, it refers to the Ruby-eyed Mottled gene Mi and not the Mottled gene Mo which is not known to be in the United States.)
And just a reminder for those not familiar with the Ruby-eyed Mottled gene. These hamsters do not necessarily have red/ruby eyes. You can have a Ruby-eyed Mottled Black hamster. It will appear to have black eyes. The eyes will only appear “ruby” when a flashlight (torch) is shined on them. (For more information on this gene, see my Mottled article.)
The Mottled Gene
The Campbells Mottled gene, in a double dose, will produce a baby which is believed to be eyeless and toothless. Such babies will be snow white, will be smaller in size than its normal siblings, and will typically die at the age of 2-3 weeks.
How can we avoid this? It is very easy. You never pair a male Ruby-eyed Mottled to a female Ruby-eyed Mottled. That eliminates this problem. Since this is a dominant gene, to get a double dose, both parents must be mottled. If you eliminate this situation, you eliminate the possibility of producing these eyeless, toothless white runts who die very young (at least through this cause).
Will breeders who violate this recommendation have better Mottleds? I have heard this theory and don’t believe it. I get the entire range of patterning in my Mottleds, and I do not breed Mottled to Mottled. I have confirmed this result with friends both in the US and in Europe, and all agree that the quality of the Mottled patterning is random. You can get a show winner equally quickly without resorting to irresponsibly pairing Mottled to Mottled.
The Anopthalmic Gene (Roan/White Bellied)
The Anopthalmic gene is similar to the Ruby-eyed Mottled gene. Only in a double dose is there a problem. In a single dose, this gene produces either a roaned animal or a white bellied animal. In a double dose, this gene produces a white baby who is eyeless. Now this baby will not die because of this defect. Actually, since hamsters don’t use their eyesight much, the hamster can live a mostly normal life (although I have heard reports that the lifespan may be shorter than normal). The question is why you would ever knowingly produce one of these hamsters. So we don’t do it if we are responsible breeders.
Again, to avoid it, we never pair a Roan or White bellied male with a Roan or White bellied female. Then, the potential for creating eyeless white Syrians is eliminated (at least through this cause). And for anyone who has not seen a White bellied hamster, they are not always easy to distinguish. In colors like Black, it is common around here for a Black hamster to have a white patch on the belly. Some of these patches are quite large. A White-bellied black would also have a white patch and could easily mimic the white patch on a Black without this gene. So you need to be very careful with this gene. You must know the lines of the animals you buy, and you must notify buyers about this gene is there is any possibility that the hamster they are buying has the Anopthalmic gene.
Breeding the Mottled or the Anopthalmic Gene to Colors Which Would Mask It
There are a couple of situations in which you cannot tell a Mottled or an Anopthalmic hamster. We’ll discuss each separately since the dwarf genes and gene combinations are a bit different than the Syrian ones.
Masking the Mottled Gene
Some colors “hide” or “mask” other colors or patterns. Let’s take a common example. There is an Albino Campbells. The Albino lacks all pigment. What if one parent of the Albino was a Mottled but carried Albino while the other parent was an Albino? You would expect to get some babies who appeared to be Albino but were genetically also Mottled. You would not be able to positively identify which Albinos were also Mottled by appearance alone. Thus, you would never want to breed an Albino from one of these litters to a Mottled or you would be creating the exact scenario above of breeding a Mottled to a Mottled. You would expect 25% of the babies to be eyeless, toothless white babies who would die.
So we avoid any pairings which could create such a situation. Now there may be rare times when someone would do this pairing for another reason. In these cases, you would always inform the new owner of the potential for this hamster to also be Mottled. Thus, they would only accept this baby into their breeding pool IF they knew they would not be mating him to a Mottled.
There is an additional gene combination which will also mask the mottled color in the Campbells. This is the Dilute Platinum. Even though we do not fully understand what creates the Dilute Platinum (REW or BEW), we do know that this combination produces an entirely white hamster and will mask the Mottled gene. Thus, it is risky to combine Platinum with Mottled. If Dilute Platinums appear, you need to treat them exactly as you would treat the albinos in the above example: never breed them to a Mottled and warn all potential buyers of the situation. Additionally, if your Platinums are light in color (as many around here are), you should minimize any breedings which pair a Mottled to Platinum. When you do these pairings, it will be hard if not impossible to distinguish the Mottled Platinums from the Platinums (at least I have found this difficult in my light-colored Platinums). Thus, make sure you notify anyone who buys from this litter that the babies may be mottled – and that they understand what that means.
Masking the Anopthalmic Gene
There is a common Syrian color gene which masks the Anopthalmic gene. That’s the Dark-eared White gene. Since this is again a pure white hamster, any pattern such as the Roan pattern is not visible. Thus you must again either avoid these pairings altogether or warn potential buyers of any DEWs that they may be getting an animal which also has the Anopthalmic gene. Make sure they understand the significance of this and that they only accept the animal if they are willing to forego breeding to another hamster with the Anopthalmic gene. Remember too that this includes any color combinations created using the DEW gene such as Flesh-eared White which is genetically DEW plus Cinnamon.
Now would this be the only gene which would mask the Anopthalmic gene? No. If you created a Black-eyed or Red-eyed white using another gene combination (i.e. the Dominant Spot Gene or the Silver Gray plus Cream), you would also face the same situation. Err on the side of caution. Always warn the buyer of the potential problem and explain it fully to them. Let them make an informed decision.
Would “masking” be the only situation which might “hide” the Anopthalmic gene? No. If the Anopthalmic gene presents itself in the White-bellied form as it does in Goldens or Blacks, you need to avoid the other pattern genes which produce a white belly. Thus, do not cross this gene into Banded or Dominant Spot. If you do, you will find it almost impossible to identify which of the white bellied babies have the Anopthalmic gene. Thus, you will not be able to breed any of them yourself and you must notify all buyers of the potential problems derived from this situation.
Personally, I would even say that you should never cross the Anopthalmic gene into the Dominant Spot gene even if you know the result will be all Roan and not white bellied babies (breeding Cream Roan to Cream Dominant Spot would be such an example). Why do I say this? I have seen hamsters bred by a local breeder who does this. It is not trivial to tell which are Roan and which are not. The color is light enough and there may be few spots. It is too easy to make a mistake. So I believe that you should just avoid all pairings of the Anopthalmic gene with the Dominant Spot gene.
So with this gene, it is just best to avoid crossing the Anopthalmic gene into either Banded or Dominant Spot. This minimizes the chance for problems.
Hairless Gene
I've added the Hairless gene to this list since improperly breeding hairless can lead to the death of entire litters. Basically hairless females should never be bred since they generally have trouble producing enough milk to sustain a litter. Hairless females must be carefully placed in pet homes who understand the potential problems which occur when breeding these animals.. Placement in pet stores would be strongly discouraged since they cannot be relied on to provide proper information on this serious issue.
As I understand it, the cells in the mammary glands which produce milk and ducts are derived from epidermal cells (the skin layer). The defect in fur deficient animals (hairless) is also an epidermal cell defect. It's the damage in the hair follicles which produces the absent coat. The defect in the mammary glands is evidenced as insufficient or absent lactation. One would think that the severity of one correlates with the severity of the other, but I have seen no research to prove this. We do know that people with hairless hamsters report that the hairless females typically have trouble raising the young.
How can we avoid this? Very easily. Only hairless carrier females should be used for breeding. Hairless males may be used safely as may hairless carrier males. All babies, male or female, from hairless lines should be carefully placed in homes who know that the line includes the hairless gene. Thus, if hairless pups pop up in later litters, people will not be alarmed. We've heard reports of people having a hairless pup in a litter and attempting to treat its hairloss problems.
Health Problems
Diabetes in the Campbells may be the most obvious example of health problems which people continue to breed. Others may include animals with kidney problems, cataracts or glaucoma, or skin diseases. It should go without saying, but you discontinue lines with these problems. If you do have a hamster with one of these diseases, there are sometimes treatments. You will see some articles in the CHA newsletter dealing with some of these problems, and it would be good to acquaint yourself with the possible treatments and/or methods to make the animal's life as comfortable as possible.
Genetic Birth Defects
Various genetic defects have been documented in hamsters. No hamster with any problem which might be a genetic defect should be used for breeding. Among the more common genetic defects we see are spinal deformities (sometimes manifest as kinked or curved tails) and missing limbs, tails, or eyes.
Hamsters with spinal deformities should never be bred. These problems have been common in Dark Gray Syrians, but they can occur in any colored hamster of any species. If the deformity is not severe, the hamster can live a fairly normal life as a pet. Just avoid breeding the hamster and discontinue the line when possible.
Also, if you have any pups born who are missing any integral body part like a limb or eye, discontinue any breeding in that line. On some occasions an animal will lose a limb due to an accident or lose an eye in a fight. If you absolutely know the loss occurred after birth, it would be safe to breed that animal if breeding will not cause undue stress or strain. If you are not sure whether the problem is a genetic defect or not (i.e. you did not see the hamster previously without this problem), do not breed the animal. It's not worth the risk, and it's not fair to your hamsters.
There have also been reports of lines producing runty animals sometimes referred to as "micros." These are animals who never come close to achieving the normal size of their siblings. They may or may not have health problems. This problem has been reported in pure lines but is apparently a more frequent problem in hybrid lines -- lines with both Campbells and Winter White ancestry. In any case, these are not desireable, and the line should be discontinued.
Aesthetic “Defects”
The Syrian Satin Gene (Sa) should be mentioned in this article even though it does not create any physical defect. The issue is purely aesthetic, and there are no known health issues associated with the Satin gene. A Syrian hamster which gets a double dose of the Satin gene will have a coat which is generally considered unattractive but reports vary. The coat can be shiny but sparse and patchy. These animals can be hard to place or sell, so most breeders avoid creating them. Luckily the hamsters don’t know that they look different, so if you breed them, just be prepared to keep all of the babies which get a double dose of the Satin gene.
How do you avoid getting these unattractive babies? Never breed a Satin male to a Satin female. It’s that easy. If you do breed Satin to Satin, on average 25% of the babies will be these unattractive double Satin babies. Remember, though, that statistics don’t work for individual litters. Thus, be prepared to have a whole litter of these double Satin babies and be prepared with cages to keep them all yourself. Always be prepared for the worst case when doing such a pairing.
Note: The situation is not the same with the dwarf Satin gene. You can breed Satin to Satin in the Campbells, and you will get all Satin babies with coat quality similar to that of their parents.
Behavioral Disorders
There are a number of genetic “disorders” which affect some hamsters in the US. I do not have research on them nor can I confirm the method of transmission of the disorders. I do know from my experience and the experience of others that they run in family lines. They are not confined to certain color or pattern genes. Above all, I know that they are not desirable traits and should not be perpetuated. (I would love to have any research on these if people are able to find any.) They also seem to be involuntary. The hamster cannot stop the behavior. Thus, hamsters that exhibit any of these traits should be retired as breeders. Their parents and siblings should also be retired. Additionally, anyone who has purchased from these lines with the intention to breed should be notified of the problem. Unless the traits are extreme, the hamsters would not have to be put down but can live out their life as pampered pets.
The first is “back-flipping.” This is common in the Campbells. The hamster starts on his feet, does a complete flip backwards, and again lands on his feet. Sometimes they add a bit of a twist and land facing a different direction than they started from. (This is different than a hamster who falls on his back and may roll or “swim” around the cage on his back.) Back flipping does not usually show up until they are at least 5 weeks of age – sometimes later. With some, it gets extreme. They back flip during all waking hours. For these extreme cases, it is best to have a vet put them down.
The second is “pacing.” Again, around here, this is a common Campbells disorder. These hamsters run back and forth across one side of the cage. Often, they only run back and forth across a few inch path. They will often beat down the shavings in that area with their incessant pacing. Again, this trait is undesirable, and these animals (and their relatives) should not be bred.
The third is “lap running.” These hamsters run circles around the perimeter of the cage. They too will beat a path into the shavings. They and their relatives should be retired from breeding.
The fourth is “waltzing” hamsters. This can appear in dwarves or Syrians. Personally I have only seen it once, and it was in a dwarf which someone brought to a show. This young hamster ran tight circles. It could not walk a straight line. Since these symptoms can also be caused by curable problems (like ear problems), these problems should be checked out by a vet. If the vet does diagnose this condition, it is probably best to put down any animals with an extreme case. Again, the parents, siblings, etc. should be taken out of breeding and all buyers of animals from this line must be notified.
The fifth is deviant behaviors. In particular, a number of people have reported that their females have chewed the ears off of their pups and their cagemates. This generally happens when the female is nursing a litter and can happen when the pups are very young. We know that the missing ears are not a genetic defect both since the male's ears also tend to disappear at the same approximate time and we have sometimes seen the pups' ears before they disappear. It is not a common problem, but I have seen it here on two occasions and heard of it from other breeders. We separate the pair so that the female does not have further litters and do not breed further from the line. The females seem to do fine once the litter is weaned, so this may be a stress associated with raising litters. Another deviant behavior which may be similar in nature is parents chewing of the limbs of their pups. We're not sure the cause, but this does happen occasionally. In any case, these are undesireable behaviors which you would never want to perpetuate.
