Black-and-Tan Rhodesian Ridgeback Genetics-Issues and
William S. Rosenthal
Why should anybody care that there are black-and-tan Rhodesian Ridgebacks? The answer is complicated. The Rhodesian Ridgeback is a young breed, less than one hundred years old. It is a breed that was developed from numerous other breeds that were crossed with native African dogs. The breed’s origin is at best murky. When the breed standard was established in 1922, the acceptable colors included what we now call wheaten (in all of its varieties) as well as other colors that were later dropped. Black-and-tan, as far as we know, was never included in that standard. That is not to say that no black-and-tans existed then. That point, however, is still debated. Some breeders are willing to admit to litters that have occasionally thrown brindles and blues, but few will admit to black-and-tans. Perhaps that is due to the mistaken belief that to produce a black-and-tan, some RR bitch has been gotten to, “over the fence”, by a Doberman or a Rottweiler. The notion of polluting the breed in that way is anathema to Ridgeback fanciers. Therefore, the question of whether black-and-tans can be produced legitimately is vital.
There are also economic issues. Breeders who can claim a “purity” of line will be preferred by the purchasers of these dogs, as well as by those who wish to breed them. Consequently, only more successful and courageous breeders are likely to admit to having these odd colored dogs in their lines. There is a sociological aspect to this issue as well. The notion of purity of breed is a concept that some people hold to more than do others. The notion of what different breeds connote in society (not to mention varieties within a breed) is of some academic interest. An informative thesis about this is presented by Sandra Swart in a paper that is referenced at the end of this article (1). The breeds discussed include our wonderful Ridgebacks, as well as the Africanis and Boerboel. A careful reading of this thesis will make clear that we are dealing here with a sociological issue that goes well beyond the science of genetics.
There are aesthetic issues as well. The breed standard does not allow for black-and-tans, although that color is not a conformation disqualification, and black-and-tans can participate in agility, obedience, and coursing. One can assume, however, that members of the public that choose to own these dogs as well as those that breed them do so because they like the way they look. There is nothing wrong in preferring the standard wheaten varieties. It is a matter of preference and there is no arguing that point. There are, of course, people who have seen Shona (a black-and-tan), who think that she is lovely and ask how they can get such a dog. I explain to them that it is just not likely. There are very few black-and-tan Ridgebacks produced. People interested in owning a Ridgeback are served best by seeking one of standard color.
A Little Genetics
What is a black-and-tan Rhodesian Ridgeback, and how did it get that way? (A question not unlike, “How did the leopard get its spots?”) To answer that question requires some information about genetics. However, fear not. I will not go over ground well documented by others who are more qualified. I will simply summarize and refer interested readers to the original sources. The answer, however, is relatively simple. Ridgebacks are colored by the Agouti series of alleles. Agouti mainly refers to the banded appearance of individual hairs. It is a trait that comes in many varieties. For Rhodesian Ridgebacks, those varieties range from a light wheaten color to a dark red wheaten color. The black-and-tan pattern, however, is part of the Agouti series. It is not unexpected, then, that this pattern occurs in Ridgebacks.
“The probable alleles at the Agouti locus, in order of decreasing dominance, are: Ay, aw, as, at and a. Therefore, at the top of the Agouti series then we have Ay, Sable - also known as 'dominant yellow' or 'golden sable' (or what we call wheaten). This results in an essentially phaeomelanic phenotype, but the hair tips are eumelanin (black). The extent of the eumelanin tip varies considerably from lighter sables (where just the ear tips are black) to darker sables - where much of the body is dark. Allele at, 'black+tan' is next. This is a primarily black dog but with tan (phaeomelanin) markings around the eyes, muzzle, chest, stomach and lower legs, commonly seen in hounds, Doberman's and Rottweilers”(1, 2). Note that at is recessive. That means that both parents must carry the trait in order for it to occur in their offspring. It also means that in its recessive form it cannot be seen. A dog carrying only one recessive at gene will appear as a standard colored Ridgeback, although there is some evidence that these dogs may appear darker, or have more dark hairs in their coat. “The Bernese Mountain Dog shows the effect of black-and-tan combined with white markings, often called tricolor” (4). Most black-and-tan Ridgebacks are actually tricolor.
There is some dispute about from where the tan point allele in the breed came. The historical record suggests that a number of different dog breeds were bred to the native African ridged dogs to produce the Rhodesian Ridgeback that we know today. Even near the years of breed standardization, owners were apparently still introducing other established breeds into the gene pool when they showed outstanding and desirable traits such as tracking, assertiveness, endurance, protection, etc. “According to Wellings, Cornelius Jr. stated, that the best dog his father ever had was out of a Collie bitch. As Halmi put it, the Collie crosses ‘could cold track... run like the wind, and to their ancestors´intelligence had been added a subtle new cunning at rounding up grazing animals. They retained the Hottentot (Khoikhoi dogs´) instinct for hunting together in a silent pack.’ It seems that the principal crosses used with the Khoikhoi dogs were Greyhound, Bulldog and Pointer. But it´s known from Selous that in 1885 Nellis had a deerhound-like dog, - in other words a large, rough-coated Greyhound. The data also supports statements, that Nellis used Airedale and Irish Terriers and Collies. He also used the terriers and bulldogs-breeds which we know are certainly part of the Ridgeback gene pool” (5). Others have suggested that Bloodhounds were included in the mix, which along with Collies, some terriers, and some greyhounds could account for the black-and-tan at alleles in the gene pool.
Elsewhere, Helgesen includes an account of Trooper Mocke's report of his sojourn with VanRooyen (p.73). "....Cornelius VanRooyen (had) informed me that the establishment of this breed is strictly due to the importation of two grey-black bitches by Fredrick Selous!" (he meant Helm, Ed.) "These bitches were crossed with his ordinary ‘Boer hound’ hunting dogs, the result of which was eventually the ‘Ridge-Backed’ lion dog as we know it today….He described the two ‘grey-black bitches’ with curly hair over the body and yellowish buff legs and points"(5). This pattern is likely the black-and-tan of the Agouti series that was diluted, as in some Doberman dogs.
Solutions-Or, When is a Problem Not a Problem?
quarters of the Ridgeback community there seems to be an irrational belief that
black-and-tans are a scourge only recently visited upon the breed. Both the
history of the breed and the genetics of dog color argue against that view.
Writers about the breed discuss the occurrence of black-and-tans, and other
colors, going back at least thirty years. As to whether it is a problem or not,
Willis (in Nicholson and Parker) states, “Essentially, as a mainly one-colour
breed, colour inheritance is not complex in this breed and the exceptions
(livers, Grey Ghosts, brindles and black-and-tans) will be relatively rare”
(3). Just how rare it is difficult to say since breeding practices influence
the incidence of black-and-tans. We do not know the incidence of black-and-tans
because they are not usually registered and are often culled. In fact, at least
one European Ridgeback organization requires culling in its code of ethics, “Pups with dermoid-sinus, absent or multiple
crowns, colour not of standard or ridgeless should be culled at
birth.”[Italics mine] In the
The remaining question, particularly of interest to
breeders, is how can the occurrence of black-and-tans be reduced or eliminated?
First, the extent of the problem must be estimated since it cannot be
determined exactly. If black-and-tans were permitted to breed randomly with
other Ridgebacks, eventually a stable and predictable rate of occurrence would
emerge. Since random breeding is not a factor, we need to ask what will be the
incidence if all black-and-tans are removed from the breeding gene pool, either
by culling or spay/neutering. The answer is that the rate would diminish
dramatically, but never reach zero. The stable rate would reach about .25% (one
quarter of one percent) (4). To put that in perspective I have relied on some
statistics compiled by Clayton Heathcock (6) from AKC breed books and
registrations. There appear to be sufficient Rhodesian Ridgeback litters
registered each year in the
Could the rate be further reduced, or even
eliminated in a particular line? Probably, but in the absence of a reliable DNA
marker for black-and-tan, Draconian measures are required. One would have to
remove not only black-and-tans from the breeding pool, but all of their
siblings and parents. Close inbreeding could mostly likely avoid the occurrence
of black-and-tans, but at what cost? Further restricting the gene pool of an
already highly inbred breed is likely to result in unintended consequences,
such as increased health problems. For the overall health of the breed, I would
argue that breeders should welcome the occasional occurrence of non-standard
colors as evidence that the gene pool still bears some connection to the
original lines that founded the breed in southern
Author’s Note and Sources
Although I have tried to approach this topic in a scholarly fashion, I am keenly aware that there are limits to the authority that I can claim. That is because the information that is available about this issue is historically uncertain, and because the full picture of dog genetics has yet to be completed. The position outlined here, however, is based on the evidence, both scientific and historical, that is presently available. It is a work in progress, and for that reason I reserve the right to amend the text as new information becomes available.
The information in the body of the text was drawn mainly from the following sources, most of which are available on-line. The reader is encouraged to pursue those sources for a fuller understanding of the history of the breed in particular, and dog genetics in general.
Swart, Sandra. Dogs and
Dogma – A Discussion of the Socio-Political Construction of Southern African
Dog ‘Breeds’ as Window into Social History. South African Historical Journal,
2. Canine Genetics Primer. Tenset Technologies, Ltd. http://www.tenset.co.uk/doggen/indexus.html
Nicholson, Peter and Parker, Janet. The Complete Rhodesian Ridgeback, Howell
4. Bowling, Sue Ann. Animal Genetics http://bowlingsite.mcf.com/Genetics/Genetics.html
David H. The
Definitive Rhodesian Ridgeback (2nd Ed.). cited by MK-
6. Personal communication
Stewart, S. H. Origins of the Rhodesian Ridgeback http://www.rhodesianridgeback.org.za/about/origins.html
Hawley, T.C. The Rhodesian Ridgeback, the Origin,
History and Standard.
Murray, J. N. The Rhodesian Ridgeback Indaba.
Copyright © 2005 by William S. Rosenthal
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