Why do Rhodesian ridgebacks have ridges? People who aren't much acquainted with this breed may wonder if those hairs are growing that way because of a previous surgery, or in some cases, may exchange them for a dog's hackles, those hairs that rise when dogs feel an assortment of emotions such as fear, arousal, surprise, insecurity, excitement, nervousness or defensive behaviors.
Instead, in the Rhodesian ridgeback those hairs are simply a unique trait that the breed sports for many centuries. Let's discover why Rhodesians have that special ridge on their backs.
A Congenital Defect
As cool as a Ridgeback's ridge may look, turns out that the ridge is actually the result of a congenital defect, in simple words, it's a birth defect.
Turns out, a Rhodesian Ridgeback's ridge is due to an abnormal migration of neural crest cell. In simple words, when the puppy is still in the womb, embryological cells inappropriately migrate in the wrong direction, leading to the ridge.
A Matter of Standard
The dorsal ridge of inverted hair found on the Rhodesian's back is such an important feature in this breed that a ridge-less specimen is considered a serious fault and means for disqualification in the show ring.
According to the American Kennel Club standard, the ridge is this breed's hallmark and regarded as the characteristic feature of the breed.
The breed standard calls for a ridge that is clearly defined, symmetrical and made of hairs growing in the opposite direction compared to the rest of the coat. The ridge starts right behind the shoulders and tapers off to a point as it reaches the hip area.
The ridge should also have two crowns (whorls) that are directly opposite to each other. Having only one whorl or having more than two is considered a serious fault.
The lower edge of the whorls are also expected to not extend further down the ridge than one third of the ridge.
A Look Back in History
In order to understand why Rhodesian ridgebacks have the characteristic ridge, one must take a glimpse into this breed's past. Historic data shows us that, although Rhodesian ridgebacks were developed in Zimbabwe, South Africa, they are actually not native to that continent.
Only one of the “Ridgeback’s” ancestors was a small native African dog with pricked ears that had a ridge and was found with Hottentot tribes. This native dog was first described by Jan Van Riebeek when he arrived at the rocky Cape of Good Hope in 1652.
Jan Van Riebeek also described a vast array of European dogs brought to Africa by the early settlers, which, when crossed with this native dog, produced dogs with ridges.
The Dutch who converted wild lands into farm lands during their many years of trading there, decided to put these African dogs to good use allowing them to hunt and defend their herds of cattle and homesteads from lions. A good Rhodesian ridgeback would corner a lion until a hunter would arrive to shoot it.
These dogs then, later on, interbred with the several dogs imported from Europe which included great danes, mastiffs, Labrador retrievers, pointers, greyhounds, and boer hounds.
Later on, breeds imported from Arabian traders and Asian immigrants further contributed to Rhodesian ridgeback's genetics.
Breeders selectively bred for the ridge as they noticed how specimens with the ridge had a tendency of making excellent hunters. A lack of ridge was considered an undesirable trait for this breed and in the past puppies born without a ridge were culled.
Did you know? The Rhodesian Ridgeback is the National Dog of South Africa and is featured on the Kennel Union of Southern Africa's official emblem.
A Dominant Trait
A little lesson in genetics reveals how a Rhodesian's ridge is passed down from one generation to another. In technical words, the presence of the ridge is an autosomal dominant trait.
Rhodesians who have the ridge either carry two copies of the ridge gene RR (homozygous) or carry just one copy of the ridge gene (heterozygous) Rr.
The Rhodesians with the ridge who carry two copies of the ridge gene RR will never produce puppies without the ridge. When crossed, all they have to do to pass down the ridge trait is to give one copy of their two ridge genes, which is dominant.
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Therefore, all puppies born from a homozygous Ridgeback parent will have a ridge, regardless of what the other parent has, but their genetic tendencies will vary, resulting in:
- puppies who have ridges and a 50 percent chance of carrying two ridge genes RR (homozygous), or
- puppies who have ridges and a 50 percent chance of carrying one ridge gene Rr (heterozygous)
When Things Go Wrong
Do all Rhodesian Ridgebacks have a ridge? As we have seen, the ridge is a dominant trait that is passed down rather easily, but if it's a dominant trait, why do Rhodesian ridgeback without a ridge pop up every now and then?
Problems arise when two Rhodesians with only one ridge gene Rr (heterozygous) are crossed. The lack of ridge is therefore the result of crossing two heterozygous Rhodesians (Rr+Rr).
The breeding of such specimens can result in the following scenarios:
- Puppies who have ridges and carry two copies of the ridge genes (which makes them capable of passing down the trait regardless of who they're bred to)
- Puppies with a 50 percent chance of having a ridge, but having only one copy of the ridge gene.
- Puppies with a 25 percent chance of not having the ridge. Puppies not having the ridge, lack the ridge gene and therefore cannot produce any offspring with ridges.
Did you know? A Rhodesian ridgeback's ridge should be fully visible in puppies from the day they are born, so don't believe breeders who say it will grow later on, warns the Rhodesian Ridgeback Club of the United States, Inc. Rhodesian Ridgebacks are born with the ridge.
A Weak Spot
The Rhodesian's ridge is the breed's most prominent feature, but this strong point is also the breed's weakest link when it comes to congenital defects.
Breeders and researchers have found a correlation between the presence of the ridge with a congenital defect known as "dermoid sinus" a type of defect that is similar to spina bifida.
The same autosomal dominant mutation that's responsible for the ridge is what also predisposes for this condition. Not coincidentally, this defect is found in two breeds in the world with a ridge: the Rhodesian ridgeback and the Thai ridgeback.
Fortunately, this genetic skin condition is rare. A dermoid sinus develops during the embryonic stage. In normal development, the neural tube separates from the skin, but in dogs with dermoid sinus, it fails to, therefore there's an incomplete separation of the skin from the nervous system, according to the American College of Veterinary Surgeons.
The sinus appears as an indentation that is found in the skin along the center of the back of the dog. This hollow tubular indentations extends deep into tissue under the skin some even reaching the spinal cord. The tube is filled with sebum, skin debris and hair and can cause inflammation and infection potentially leading to infection of the central nervous system.
When the spinal cord is involved and becomes infected, affected dogs may have permanent consequences and several die or need to be euthanized due to severe illness and pain.
Dermoid sinus in Rhodesian ridgebacks can be diagnosed through x-rays by injecting dye into the indentation. The only type of treatment for this condition is surgical removal.
Being hereditary, puppies with condition should have the abnormal tissue removed and they should be altered (spayed or neutered) so to prevent them from passing down this defect.
An Ethical Problem
The best way to eliminate the risks for dermoid sinus, once and for all, would be working on producing ridge-less specimens. This clashes though with breed standards which emphasize the importance of the ridge and many owners of these dogs are particularly fond of this characteristic.
Problems though may arise when crossing ridge-less specimens because when a gene pool is narrowed, there are heightened risk for exacerbating other problematic genetically inherited traits.
The only solution may outcrossing with other breeds, but of course his may impact the looks of this breed.
Legend Has It
A cute explanation for why Ridgeback's have their characteristic ridge comes from The Rhodesian Ridgeback Club of the United States’ Health & Genetics Committee.
For those who think the ridge looks like a surgical incision gone bad, owners can give this explanation:" Oh, you're talking about that ridge? That's "where God sews them up when he’s done stuffing them."
Did you know? The only way to tell whether a Rhodesian has one or two ridge genes is through genetic marker testing, which is now provided by the GenoCan project.