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What Is Seal, and Why Haven't You Noticed It Before?

This color is almost never discussed, but is widespread in a number of Molosser breeds, most notably the Cane Corso

Spend enough time in the Corso ring, and you’ll begin to notice an interesting phenomenon: a surprising number of heavily brindled dogs whose striping appears to be an odd shade of black.

(If you’re a Corso person, you might want to stop here and read our short story on Corso-specific color terms. Corso culture seems to exist a kind of parallel universe, employing definitions for basic dog terms that do not reflect what the rest of the dog world means — oftentimes, meaning quite the opposite. In the Corso world, most seem to think the black is the base coat, when in fact it is the color of the striping.)

On the dark end of the spectrum, this brindle striping appears a more diffused, almost matte-appearing black — not the deep raven tones of a true black. On the lighter end, the stripes appear to be a deep, chocolately brown.


The hue of this odd-colored brindling can range from a matte black (above) to a coppery, dark brown (below).


The Cane Corso standard doesn’t mention this odd not-quite-black color. And genetically speaking, brindle is always black, unless acted upon by a dilution gene. (For an explanation on how this works, see our story about brindle basics.)

So what is this color, exactly?


Red Alert


There are two possibilities for this coppery-brown brindling in a Corso. One is permissible according to the breed standard, and one is not.

Let’s look first at the incorrect source of these chocolate-colored stripes.

A brown cast to brindling can be caused by the red dilution gene (written in genetics-speak as “bb”), which turns all the black on the dog to red. (This is the same gene that produces reddish-brown brindle stripes on a mahogany Neapolitan Mastiff.) Determining whether or not a Corso’s brindling is caused by this red dilution gene is simple enough: Just look at the nose. If it is red, the dog is a red dilute. That’s because the red dilution gene also affects pigment, turning the nose color from black to red.


This dog was identified as a Cane Corso on a popular stock-photo site. The incorrect brown nose, however, indicates that this dog acquired its brownish brindle coloring through the incursion of another breed.


Red pigment is of course unacceptable in the Corso. Indeed, any judge who determines that the pigment of a Corso is red, brown or liver is well within rights to excuse the dog for color not in accordance with the standard.

But these Cane Corsos with dark, reddish brown stripes have black noses — not red or brown, as you’d expect to see on a red dilute.

So what exactly is going on here?


Signed, Sealed, Delivered


The answer lies in a relatively rare color known as seal.

The Boston Terrier standard lists seal as one of only two colors acceptable in the breed, and describes it this way:

“Seal appears black except it has a red cast when viewed in the sun or bright light.”

To illustrate, consider these two photos of the same Boston Terrier in different lighting. Inside, for all intents and purposes the dog appears black. But when taken outside, all kinds of red highlights appear in his coat.


Seal looks different, depending on the lighting. This is the same dog, seen indoors (left) and outdoors (right), which makes the coppery tones in his black coat more apparent. Photos: Chad Howard.


Referred to variously as “incomplete dominant black,” “modified dominant black” or the rather inelegant “bad black,” seal becomes obvious when placed next to a true black dog.

Another breed where seal appears — in its brindling — is the Boxer, a breed that indisputably has been inserted into the Corso.

Compare the puppies in the Boxer litter below. At far right is a fawn with no brindling. The remaining four puppies are what is called “reverse brindle” — their black brindling is so heavy as to make it appear as if black is their base coat (which it is not).


A Boxer litter with four reverse brindles. Two are seal brindle (as is the dam) and two are black brindle. While seal can be difficult to identify on its own, when placed next to true black, the difference is obvious. Photo: Michael Shepherd.


Two of the puppies are seal brindle (far left), and two are black brindle (center). Notice how the seal color appears less vibrant and concentrated on the two seal puppies at far left, and instead is more matte or muted.


Color This Complicated


Unfortunately, to date geneticists have not quite figured out how seal works, even though it is present in several breeds, from Poodles to German Shepherds. There is no identifiable “seal” gene. So we are left to puzzle things out through visual appearance, and the presence of other genetic color markers. 

While dogs are a certain color on the outside, that isn’t the only color in their genetic backpack, if you will. They may be carrying other colors that do not appear in the dog’s phenotype, or physical appearance, because other, more dominant colors block them out. In the Corso, for example, black (or the K gene) is dominant over fawn or red (ay).

This is the key to seal-brindle Corsos: They are dogs with fawn or red base coats whose brindling has been turned a faded shade of black to Hershey-chocolate brown. This is because of the seal factor, which allows the fawn or red base coat to break through the dominant black coat that has been covering it up, if you will.

In addition to the gold, red or brown sheen on the black in their coat, seal dogs typically have a stripe of the black coat down their midline and black on their face, tail and lower legs. Indeed, black shading on the feet up to the pasterns is found on many seal brindles.


Black shading on the feet is common in seal brindles.


Because seal is particularly hard to see on dilutes, it also may be present in gray dogs and gray brindles (brindled fawn dilutes, or called formentini), but may be so subtle as to not be readily identifiable.



Solid, Man


Since the mysterious seal factor affects the black color in brindling, does it also affect the black in solid-colored black dogs?

Why, yes, it does.

Some solid-colored black Molossers can appear to have a reddish tinge to their coats, especially when they are outdoors in bright light. But unlike so-called sun-burned black coats, which have uniformly reddish tips, in solid seal dogs these copper-colored areas are unevenly distributed, often appearing as if parts of the coat have been rusted.

Oftentimes, the seal color is not readily apparent, especially indoors — until the seal dog is placed next to a true black dog. Then, the difference between the two blacks will become glaringly obvious, just like the Boxer puppies in the above photo.


Perhaps the ultimate solid-seal Corso was Basir (above), the dog on which the Corso standard was based. Contrast him to the non-seal solid black Corso below.


Dilute dogs (that is, grays or blues) with or without brindling can also be affected by the seal factor. However, because all the colors are more diffused due to the dilution, the reddish tint of the coat is often much more difficult to detect.


Seal is difficult to photograph, and it is even harder to capture on a dilute. But the reddish undertones are visible on the cheeks and abdomen of this gray seal puppy.



Origin of the Specious


Where, you might ask, does the seal color in Cane Corsos come from?

As we’ve noted above, seal exists in the Boxer, a breed that of course has been introduced repeatedly into Corso bloodlines.


A seal brindle Boxer. Note that the black stripes are not as vibrant as in a true black brindle dog.


Where did the Boxer get its seal from?

While we can’t know definitively, the Boxer’s elegant form likely comes from a Sighthound ancestor somewhere along the line. And seal — believed to be a color of ancient origin — is found in the Afro-Asian Sighthounds, like this seal Indian Caravan Hound.


Seal is a common color in the native but now rare Indian Sighthound called the Caravan Hound. On a side note, Sighthound buffs should take a good, long look at this truly purebred example, as so many Caravan Hounds proliferating on the internet are simply mongrels. Photo: Neil Trilokekar.


Indeed, southern Italy’s proximity to North and West Africa ensured a steady stream of trade, before, during and after Roman times. The levriero meridionale, a sort of landrace Sighthound found around Rome, is a testament to this canine communication between the two continents. Seal is an acceptable color in the Italian Greyhound, so its presence in the Corso should hardly come as a surprise.

And there is another contributing breed to the Corso in which the seal factor is also at play: the Neapolitan Mastiff.

Mastini can either be solid black, or reverse brindles (heavily brindled dogs that appear primarily black, with their fawn/red undercoat giving the impression of being the striping). And, like Corsos, they too can exhibit the seal factor, which renders their black color a muted, often coppery shade of black — again, a fact that becomes readily evident when they are placed alongside a true black Neo that does not carry seal.


Compare the seal black Mastino above with the true black Mastino below. 

Bottom photo: Cinciripini Mastini.


Interestingly, once one is aware of seal in Molossers, the more one finds. The color is not uncommon in Boerboels, as the below photo attests.


Seal brindle appears fairly frequently in the Boerboel, too.



Seal Brindles in the Ring


What should conscientious judges do with seal-brindle Corsos, as the color/pattern is not described in any standard?

The following is my opinion only, as it is a question I pondered when I became aware of the presence of this pattern in the breed. Indeed, it was the impetus for this article.

Because no one understands the mechanism by which black coats or brindling become seal, eliminating seal from the gene pool is a virtual impossibility. In the Corso, this reality is compounded by the fact that two major contributors to the gene pool — Boxers and Neapolitan Mastiffs — also carry the seal factor. To eliminate seal-brindle Corsos would throttle an already struggling breeding pool.

Then there is the historical factor: Seal brindles — and their solid counterparts — have been part of the breed since its inception. Many of the early American and Italian dogs were arguably seal. Attesting to this is the fact that in the Corso community, seal brindles are not at all controversial, and are readily accepted by breeders on both sides of the Atlantic.


Above: American foundation dog Ch. Cocomo, whelped 1988. Below: Seal brindle at the kennel of Italian breeder Umberto Leone, 2000. Photo: Shauna DeMoss.


If a judge were to argue that seal brindles should not be rewarded, then in the name of intellectual consistency that judge also would need to toss seal Boxers out of the ring — in particular because the AKC Boxer standard takes great care to note that the brindling should be “black,” which is not the same as seal. And who’s going to do that?

In short, I personally have zero problem pointing to this color or pattern in the Corso ring.


Ghost Tan Points


The seal factor also produces another color phenomenon that can crop up in the Corso: ghost tan points.

These markings are of particular interest because of the disqualification in the Corso standard for the black-and-tan pattern.

(Time out for a personal rant: There has been an irritating trend recently to try to shoehorn any non-standard pattern into the black-and-tan disqualification, arguing that “any solid color” means that any pattern that appears with a solid color should be disqualified. Uh, no. The disqualification was written to underscore the fact that the black-and-tan pattern can have different base colors — not just black. The Corso can carry dilution genes that change the black base color — to gray in the case of the blue dilution, for example. All this is not to say that non-traditional, non-black-and-tan patterns are acceptable — hardly. It just means that judges with any knowledge of color patterns would be hard-pressed to formally disqualify them under the black-and-tan disqualification. But they can certainly excuse them from the ring for lack of merit or color not in accordance with the standard if that is their assessment.)

Back to ghost tan points: Black and gray dogs that exhibit this pattern are in fact black and tan. At the A allele, which produces this pattern, they are genetically “at at,” which is black and tan. But they also carry dominant black, which covers up their black-and-tan pattern.

As we have learned, if the Corso also carries the seal factor, its underlying light colors can bleed through the black. This is what happens with dogs that display ghost tan points: The tan points of their traditional black-and-tan pattern are being revealed by the seal factor.

Sometimes, the tan points show a faint brindling, too. That’s because, in addition to being black-and-tan and dominant black and seal (does your head hurt yet?), these dogs are also brindled. The brindling is visible inside the tan areas, but, because of the seal factor, is appears to be a faded black or dark-chocolate color.

This discussion involves “ghost tan” points on black or dilute gray Corsos only. Such Corsos are genetically black and tan (at at), and as a result they will pass a copy of the black-and-tan gene to every single one of their progeny. Given that the goal should be the elimination of this pattern on the breed (which already exists at alarmingly high levels — a 2019 study found that almost a quarter of Cane Corsos are carriers), as well as the fact that the ghost markings affirm the genetic presence of the black-and-tan pattern, the general consensus — including that of the parent club — is that this pattern should be disqualified on black and gray dogs whose seal factor makes the tan points visible.

Markings that resemble tan points can also appear on fawn or red Corsos, but that is a different genetic pattern that has nothing to do with seal (instead, it is related to sabling), and is a separate discussion entirely.



My appreciation to Stefanie Henneboehl of www.coatsandcolors.com for her input and clarification of the genetic terms used in this article.




© Modern Molosser Magazine. This article may not be reposted, reprinted, rewritten, excerpted or otherwise duplicated in any medium without the express written permission of the publisher.