Hello everyone,
Before delving into the topic, I want to give an introduction and some background information to lend some credence to this post. I started off with Campbell hamsters in the mid-90s when I was about 9, had a Syrian as well as another Campbell (and chinchilla) when I was a teenager, and largely expanded with a (perhaps) Winter White as well as several Roborovskis/Syrians (plus a couple mice and another chinchilla) in college. My hamster keeping took a giant pause throughout my 20s and much of my 30s (hence the glaring omission of Chinese hamsters, which I do not think were even in the US then, but I also grew up in CA, where it seems they're still illegal to this day) until a couple weeks ago when, due to my children's increasing interest in hamster videos, I decided to get a pair of Winter Whites (always my favorites given their absolute mythical status in the US during the 90s/aughts). This has led to my refamiliarizing with the hamster community and learning modern perspectives on hamster husbandry practices.
All of this is to say that I have a fairly extensive and diverse experience that I think offers a unique perspective to the hamster community. More important though (at least for the sake of this post) is my career path. I am a professionally trained (i.e. doctoral degree) population geneticist who is currently employed at an esteemed research institution and has a healthy publication record in peer-reviewed journals regarding introgression (i.e. the process of hybridization). At this point, I want to note that my username is my real name; you can Google me (I have a pretty unique name) or peruse my papers on Google Scholar (though without academic credentials, some are behind paywalls). The reason I'm committing this cardinal sin of violating my Internet anonymity is because I hope that my words, backed by my credentials, can lead to increased widespread education of this group of animals that I have a life-long integral passion for.
So first, it is oft-repeated that "you can never breed out the hybrid lineage". From a purely mathematical, basic theoretical point of view, this is patently false. There was a college upper division biology course that I taught where my mentor would emphasize that there is a strong distinction between genealogy and genetics, namely that just because someone is your ancestor (genealogy), it doesn't mean you share any genetic information. The reason for this is the finite amount of genetic information that is inherited each generation, which is particularly exacerbated by the genomic phenomena of linkage disequilibrium. Another way to think of this is that DNA is not infinitesimally divisible, similar to the concept of a half-life with radioactive decay. To put it simply, you half the amount of genes passed down each generation, and after some generations, the contribution of any one particular ancestor is highly likely to be lost entirely in any one descendant. This process is especially quick in hamsters with their ~0.5 year generation time vs. humans and their 25 year generation time. What this means is that you tend to have a relatively high relation to a very small proportion of your ancestors, with absolutely no genetic relation (despite a genealogical one) to the vast majority of your ancestors. Thus, let's say there is just one Winter White ancestor 10 generations ago; this degree of relation is probably small enough that it's quite plausible that many of the descendants would have absolutely zero Winter White ancestry.
Now, this argument can be rather pedantic considering that most people probably feel that there are quite a few Campbell individuals involved in the non-pedigreed White White lineage and vice versa. However, that brings up another well-spread idea that is highly likely a myth: "purebred" Campbell/White White individuals are assured due to a pedigree, ideally one that traces to wild caught individuals, because hybrids do not occur in the wild. Here's the real truth to the matter, and this goes to the heart of several very active research topics in the field of population genetics, ecology, and evolutionary biology (namely introgression/hybridization, population structure, speciation, species concepts, and even species distributions): hybrids occur all the time in nature, and are perhaps even critical to the perseverance of a species in certain cases. This has been well supported to have even occurred in us, anatomically modern humans, and there is growing evidence suggesting it has actually happened several times in our history.
A possible counterargument to this that I've seen many times is that Campbells and Winter Whites do not co-occur naturally. I have not seen anything in the literature supporting this, and in fact, quite the contrary. There is not much research into wild hamster populations, especially currently, but what little there is seems to suggest that there is indeed co-occurrence. Granted, there are noted behavioral differences, but that's why there is any speciation at all; hybridization would indeed be rather uncommon, but that doesn't mean it doesn't have a drastic impact overall on populations. Also, species distributions are not easily conjured; unless a species distribution is statistically modelled (and even this has substantial limitations), it is still largely a guess, and a weak one at that without a lot of active naturalist observations and/or active biogeographic research. The native regions for these species are pretty sparsely populated by people, so I highly doubt anyone really knows their true distributions, thus overlap can actually be quite high. I'll admit that I cannot definitively say anything about naturally occurring hybridization in these species, and that my literature search was rather cursory, but as someone who has done a large amount of research in this field, it would be a very poor bet to say that natural hybrids do not occur.
Moreover, the very act of domestication, despite any argument of whether hamsters are "truly" domesticated, already highly diverges the "pet population" of each hamster species significantly from their naturally occurring brethren, especially without additional contributions of wild individuals. This is perhaps exacerbated if collection occurred within a particular geographic region, though conversely, collecting across the range then results in another form of introgression, so either way, the establishment of a captive population pokes holes into the idea of a "purebreed" as far as it relates to natural populations. On a related note, the pressures of artificial selection, e.g. preferring certain colors or tame behaviors, drastically and very quickly changes a population, and quite possibly even more so than so-called hybrids (depending on the degree of hybridization naturally versus in captivity). Additionally, the health consequences of this are quite possibly much more detrimental than hybridization as well; while there is research that supports inbreeding to be perhaps not as detrimental as we previously thought, the ill effects of domestication are still pretty prevalent, for example the ailments that commonly affect nearly every breed of purebred dogs. Ethical breeders may argue that they have stringent practices in place to discourage genetic disorders, and I'm not denying that those efforts are important, but at the end of the day, it's still nowhere to the scale of the genetic diversity that occurs in the wild. As a result, I would posit that, while not intentional, it is perhaps a bit hypocritical to so harshly demonize hybridization while simultaneously engage in breeding for specific traits (especially new color mutations).
Another aspect to consider is hybrid vitality. There are different things being said, so I'll address the two extreme positions. One extreme is that without "proper breeding standards", hybrids will run amok and degrade both species. If this were indeed the case, then first off, this would be highly suggestive that hybridization probably does occur to a high degree in the wild, thus "purebreeds" just simply don't exist anyway, as aforementioned. Second off, while hybrids certainly can lead to poor quality individuals, it can also instead lead to exceptional individuals (or at least individual beneficial traits) and thus be an important process for fitness and speciation, a phenomena sometimes referred to as hybrid vigor (which might perhaps be especially important for the relatively genetically homogeneous captive populations). I couldn't say whether this occurs to any degree in the two Russian Dwarf species, but it's certainly worth considering. The other extreme notion, which kind of runs contrary to the previous, is that hybrids are extremely unfit (and this is sometimes coupled with the argument that hybrids do not occur naturally), in particular inciting poor health conditions (e.g. bringing diabetes into Winter Whites, and I once read that supposedly there is a genetic disorder going the other way into Campbells too, but I forgot what). If this were true (which does not seem to necessarily be the case due to many known cases of viable F1 hybrids), then the two species would naturally be kept fairly "pure" anyway through natural selection. Specifically, selective pressures against hybrids with poorly adaptive traits (which by the way, is not mutually exclusive to having beneficial traits) prevent rampant hybridization to the point of degrading species boundaries, which is in fact a naturally occurring process called reinforcement (though this is a bit of a controversial hypothesis). Let's now address the big elephant in the room: large-scale commercial hamster mills supplying the big chains and even independent shops, what might be called the pet industrial complex, which let's face it, is 99.9% of all captive hamsters at this point and really dictate what is the mainstream Campbell vs. Winter White. Sure, one could say this industrial complex doesn't care and will just keep pumping out terrible quality individuals without a care for species identity. While that's certainly plausible, there's a few considerations. One, from what I can tell, the same supplier(s) to the stores are the same ones to scientific laboratories (including medical ones), and that creates a stricter control on keeping lines "pure" (though it's unclear if hamsters are still used in labs in the US). If hybrids were truly in such terrible condition, I think the combined reception from both the pet and lab consumers would force them to at the very least not just haphazardly mix different species. At the end of the day, it's the almighty dollar that speaks, and that requires at least a modicum of scrutiny and care, even if it's not to your or my standards. Plus, I read that fecundity decreases in hybrid pairings, further discouraging the practice. Also, considering that stores indeed identify a difference between the species nowadays, that does suggest there are separate lines being kept, thus there doesn't seem to be an incentive to integrating them for no reason.
So what does this all mean? First, I have virtually no social media presence, and am not a member of any other forums (despite having many other hobbies and interests), but I was strongly motivated to actively join the online hamster community because I was saddened to see that "hamstering" seems to have largely wilted since my childhood/young adult days. I think this is largely due to certain gatekeeping behaviors regarding breeding and husbandry (which I would like to comment further in the future if there is a warm reception here), and some of that stems from the idea of pedigrees, to which this hybrid issue is germane. So my goal here was to correct some misinformation about the Russian Dwarfs and the perception of hybridizing, and have prospective dwarf hamster keepers instead rely on the morphological differences between the two species. In other words, if an individual exhibits all of the traits associated with the species label s/he was given, then that effectively is the correct species (and actually how field biologists would ID them). In particular, I find that the most reliable trait is the thick black ventral striping with minimal/zero browning coupled with a diamond-ish black patch on the forehead in the Winter Whites (only works well with agouti/sapphire morphs); the next indicator for Winter Whites is a skull/face shape that I personally think more resembles the Chinese hamster (people fixate on the nose, but I find that can be difficult sometimes, especially depending on the angle; I would say looking straight in their eyes, they have kind of a more triangular shape due to that nose dropoff, whereas the triangular shape cited with the Campbell is more from the bird's eye view; the Campbells seem to often have puffy noses, maybe a wider skull, and perhaps more angled eyes; the ear diagnostic is difficult based purely on size, but I noticed that the Winter White's ears will often crinkle, which I think is more the reason for the visual effect of appearing smaller; and finally, Campbells will usually have those "buffed out" shoulders giving an hourglass figure, whereas Winter Whites look pretty linear, again more resembling a Chinese hamster, but without the tail and a shorter length). Only when these traits are very mixed, or if you see distinctively Winter White traits on a Campbell morph (though contrary to popular opinion in the US, it seems there are certainly native Winter White morphs/patterns beyond the "classic 3", plus you never know what may be a new mutation) would I say using the term "hybrid" is needed (and like with dogs, if one phenotype is still much more dominant, the phrasing "Winter White X" or "Campbell X" I think is appropriate). I'll also add that the somewhat popular conception that Campbells are more social seems to be backed by at least one scientific paper, which found that biparental care is obligatory in Campbells but facultative, i.e. optional, in Winter Whites. Moreover, I remember in the early aughts, it was a pretty popular notion that Winter Whites were friendlier and less likely to bite; no one seems to be saying this now, perhaps it's been completely debunked, and I really have no standing on this, but I'd be interested if this actually had truth to it, as my personal anecdotal experience is consistent with this observation. Anyway, these behavioral traits are by no means diagnostic, but thought I'd share.
I hope this long read has been informative to at least some, and I'm looking forward to some conversation over it. Please feel free to challenge or debate any points, I welcome a healthy discussion regarding this matter, and I know some things really fly in the face of a lot of the conventional thought out there, so I want to respectfully address other points of view.
