What Causes the Ridge on a Rhodesian Ridgeback?

The Rhodesian Ridgeback is an impressive breed. Muscular, yet lean, with a beautiful red wheaten coloring, it is best known for its prominent stripe of hair that runs down along its spine in the opposite direction of the rest of its coat.

What Causes the Ridge on a Rhodesian Ridgeback?

In a word: Breeding.

Centuries back, when European settlers made their way to the South African Cape, they brought with them a variety of dog breeds from their native countries, many of which fared poorly against insect bites and deadly diseases native to the area.

At the same time, the settlers also discovered a small, native dog belonging to the nomadic Khoikhoi people of the region that was impervious to such diseases.

In addition, these settlers found some of the native dogs had a distinctive ridge down their backs while others did not. And they soon discovered that those dogs with ridges had a tendency to be clever, excellent guard dogs and hunters, so efficient they could even corner lions and keep them from attacking their cattle.

In time, European settlers began interbreeding the native dogs with their own imports, culling from each litter those puppies born without ridges. The practice seems cruel by today’s standards, but the interest then was not in creating companion animals.

At any rate, the interbred dogs included mastiffs, greyhounds, great danes, boer hounds, and labrador retrievers. As well, they were also crossed with imports from Asia and Arabian traders all of which contributed to the genetic history of the Rhodesian Ridgeback.

Despite the breeding, there were and still are occasions where Rhodesian Ridgeback puppies are born without ridges.

What Determines If a Rhodesian Ridgeback Will Be Born With a Ridge?

These days, ridgeless Rhodesian Ridgebacks are less common but whether or not a dog is born with or without one is a matter of genetics.

The ridge is the result of a simple autosomal dominant trait. That means, in order for a Rhodesian Ridgeback to be born with a ridge, the dog must carry at least one copy of a ridge gene. A ridgeback with two copies of the gene is referred to as homozygous, while a ridgeback with one copy only is called heterozygous.

Simply put, this means that a puppy with at least one homozygous parent will always be born with a ridge. However, if both parents are heterozygous, then there can be a 25 to 50 percent chance that their offspring will not have ridges.

What Do the Ridges Look Like?

Two whorls of hair located near the breed’s shoulders form the start of the ridge which then runs down the length of its spine tapering near the end at about the hips.
The opposite-direction growth on a Rhodesian Ridgeback results in his fur standing up on end and can sometimes confuse people into thinking his hackles are up and he is on the defense.

The American Kennel Club exacts certain standards for the Rhodesian Ridgeback ridge. A dog with only one whorl also called a crown, or a dog with more than two will be seriously faulted in the show ring. Additionally, the AKC expects the bottom edge of the crowns to not go more than one-third of the way down the ridge.

Is There a Genetic Marker Test for the Ridge?

A marker test would be immensely helpful for breeders in determining whether their dogs will produce ridged litters. But while we’re not there yet, ongoing research at the University of California at Davis has shown promise.

In 2003, in an effort to isolate the specific gene that causes the ridge, researchers began collecting samples of DNA from both ridged and ridgeless Rhodesian Ridgebacks. The laboratory has since mapped out the region of the genome but has not yet identified the responsible gene. Once they do, researchers hope to continue their work in hopes of identifying the genes that determine differences in ridge patterns.

By the way, if you’re thinking of purchasing a Rhodesian Ridgeback puppy, you’ll know right away if he is of the ridgeless variety as it’s not something that develops months after birth. Rather, a Rhodesian Ridgeback puppy will be born with his distinctive wrong way coat line readily visible. That’s because the development of the ridge begins in utero. It’s actually a genetic mutation where embryonic cells migrate in the wrong direction causing the ridge to form.

So It’s a Birth Defect?

It is. But in breeders’ circles, a desirable one. In fact, the ridge on a Rhodesian Ridgeback is the primary requirement for American Kennel Club competitions and without one a dog cannot be registered nor compete in AKC conformation show rings.

A more serious congenital defect that doctors and researchers have found correlates directly to ridged dogs is a rare skin condition known as dermoid sinus. Often compared to spina bifida, dermoid sinus shows up as a hollow tubular indentation in the skin that can become inflamed and infect the central nervous system. X-rays can help diagnose the condition and it can be treated by removal of the sinus.

Final Thoughts

While we know what causes the ridge on a Rhodesian Ridgeback, we may never know why those born with ridges have historically resulted in smarter and better guard dogs and hunters. That may be a question for the ages.

By the way, Rhodesian Ridgebacks were originally called African Lion Dogs for obvious reasons, and in some ways, they may be quite overdue for another name change. After all, in case you’re not up on geography, Rhodesia no longer exists. The country was officially renamed Zimbabwe way back in 1980.

Then again, maybe it’s best left alone. If you’re a fan of alliteration like some of us are, Zimbabwe Ridgeback doesn’t have quite the same ring to it, does it?