Whenever anyone tells of seeing a coyote (Canis latrans) in a heavily populated area, they are met with the inevitable question, "Are you sure it wasn't a dog?" The response is usually short on specifics but often long on emphasis: "It didn't look like a dog." But, of course, a coyote does look like a dog (Canis lupus familiaris). Just not exactly.

One commonly cited difference is that a coyote has longer legs than a dog has. I've used that description myself, but I always felt a little uncertain. When I really thought about it, I realized that "longer legs" isn't quite accurate. In general proportions, a coyote is somewhat longer than it is tall, and so is a typical dog. A few breeds of dogs, notably the sighthounds (dogs like greyhounds), are taller than they are long.

No, a coyote does not actually have longer legs than a dog has. But there is an unmistakable impression of "legginess" about a coyote that distinguishes it from a dog.

After puzzling over it for a while, I realized what it was. A coyote's "elbow" lies below the line of its sternum, and a dog's "elbow" is higher than its sternum.

Remember that a dog, like most mammals, is digitigrade, meaning that it walks on its toes. On a dog's front leg, moving up from the foot, the first joint corresponds to the human wrist. The segment of the leg above that corresponds to the human forearm. It is the longest part of the dog's leg, and it is comprised of two bones side by side (the radius and the ulna). The next segment, corresponding to the human upper arm, is comprised of a single bone, the humerus, and it is very short by comparison.

The joint between these two main segments of the foreleg, the "elbow," is what clearly shows the difference between a domestic dog and a coyote or, for that matter, any wild canid. (There are rare exceptions, but I'll get back to that later.)

Chaos, the German shepherd, represents a dog with a somewhat close resemblance to a coyote. His "elbow" is a good couple of inches higher than the underline of his chest. Photo by Charles J. Bonner

Titan, the Boston terrier, represents a dog whose build is entirely unlike that of a coyote. Yet even Titan's "elbow" is distinctly higher than the underline of his chest. Photo by Charles J. Bonner

A coyote attacking a sheep. His "elbow" is a couple
of inches below the underline of his chest.
Photo by U.S. Dept. of Agriculture, public domain

My son's German shepherd, Chaos, is a fairly typical domestic dog, and one that looks superficially similar to a coyote. His "elbow" joints are much higher than the underline of his chest. Even a decidedly un-coyote-like dog such as my other son's Boston terrier, Titan, has his "elbows" higher than his sternum. The same is true of just about every dog I've examined (with a few exceptions, which I'll get back to). A picture of a coyote clearly shows the "elbow" well below the underline of the chest.

Now, why is this? Is the coyote's humerus proportionally longer than that of the dog? Maybe so. I can't tell that without launching a full-scale scientific investigation which would be, frankly, beyond my resources. But for field identification purposes, it is not really necessary to be that rigorous.

Look very closely at these and other pictures of coyotes, and you will see that the real difference is that the dog's chest is proportionally deeper than that of the coyote.

Even in this face-on view, you can clearly see that
the coyote's "elbows" are lower than its chest.
Photo by Marya/emdot, licensed via Creative Commons license.

We can take this beyond the coyote and compare the relative height of the elbow and sternum in several other canids. Whether we're looking at foxes, wolves, jackals, or even the bizarre maned wolf, the pattern is fairly clear: Domestic dogs have deeper chests than other canids, and a dog's elbow joint is higher than the underline of its chest.

The red fox (Vulpes vulpes) also has its elbow well below its chest. Photo by Charles J. Bonner		The maned wolf (Chrysocyon brachyurus), the tallest of the wild canids, is taller than it is long. In its stride, its left "elbow" has risen higher than its chest, but you can see by its outstretched right leg that its "elbows" are normally lower than the chest. Photo from Polish wikipedia, licensed under GNU Free Documentation License.
A stalking southern red wolf (Canis rufus). Its "elbow" is well below the level of its chest. Photo by Tim Ross, public domain		Even running at full tilt, this southern red wolf (Canis rufus) shows its "elbow" below its chest. Photo by U.S. Fish and Wildlife Service, public domain.

A gray wolf (Canis lupus occidentalis) standing on a
road in Yellowstone National Park. In its heavy winter
pelage, it is a bit difficult to see that its "elbow" is
just about on the same level as the underline of its chest.
Photo by Jim Peaco, U.S. National Park Service, public domain.

The gray wolf is the most equivocal of the wild canids in this regard. A gray wolf's chest is a bit deeper than that of a coyote, and its elbow joint is just about on the same level as the underline of its chest. This can be rather hard to distinguish when the wolf has long fur, as they often do.

But so far, it looks like a good rule of thumb: A domestic dog's elbow is higher than its chest, and a wild dog's elbow is at or below the line of the chest. (We'll get back to the real exceptions later.)

Now, why do dogs have deeper chests than their wild relatives, especially their very close relative, the gray wolf?

I don't really know, but my guess is that it has to do with the way the earliest domesticated ancestors of today's dogs lived alongside our own primitive ancestors. While there is considerable debate and disagreement among experts on the subject, there is one inescapable fact about primitive dogs: Among the most primitive of existing domestic dogs are the sighthounds.

The elegant, refined greyhound is a poor example of what I'm talking about. Better examples are the primordial sighthounds that still exist, such as the sloughi and the Azawakh (also known as the Tuareg sloughi). These dogs were bred, not by a conscious process of selection for desirable traits, but by something more like natural selection. Only the best hunting dogs were provided with food and permitted to breed.

Consider the way a primitive dog hunted with a group of humans as compared to the way a wolf hunts with its pack. A wolf can rely on all members of the pack having roughly equal strength, stamina, and general hunting prowess, so no individual wolf bears any particular burden in the hunt. By contrast, a dog hunting with a tribe of human hunter-gatherers is the fastest runner and has the best stamina by a long shot. It is the dog's job to range far and wide, seeking out the game and chasing it toward the humans with their spears and arrows.

The humans then rewarded the fastest and best endurance runners among their dogs by giving them food and breeding opportunities.

Over thousands of years, this process resulted in a dog with much greater speed and stamina, even than its wolf ancestors. And among the physical traits that made this speed and stamina possible was a very deep chest.

Since today's sighthounds are much more primitive than other domestic dogs, it is likely that all of the more refined domestic dogs of today descend from ancestors which had been subject to this same selective pressure. In other words, even the Boston terrier of today has a deep chest that he inherited from his primitive sighthound-like ancestors.

I am not suggesting that every domestic dog is descended from something that looked like a sloughi. Only that some of the selective pressures that turned a wolf into a sloughi were at work on the earliest domestic dogs, and that modern breeds of dogs derived from something that was on its way to becoming a true sighthound.

Now, what about those exceptions I mentioned earlier? Well, there are two. Those would be the sighthounds and other primitive domestic dogs.

In most sighthounds, the elbow joint actually is lower than the underline of the chest. However, this is obviously not a matter of having a shallow chest. The sighthounds clearly have proportionally longer humerus bones than other dogs.

Despite her very, very deep chest, this greyhound's "elbow" is lower than her chest. She has a very long "upper arm" compared to other dogs. Photo by Neurodoc, licensed under GNU Free Documentation License (GFDL).

The sloughi or Arabian greyhound also has a very long "upper arm" such that his "elbow" is well below the underline of his chest. Photo from Wikimedia Commons, public domain.

The azawakh or Tuareg sloughi also has a proportionally
long "upper arm," such that his "elbow" is lower than his
deep chest.
Photo by ABIS, licensed under GNU Free Documentation License (GFDL).

Still, this does not lead to confusion. Nobody is going to say, "I'm not sure it was a coyote. It might have been a greyhound." The difference between a coyote and a sighthound is abundantly clear, even though both have long legs.

Doesn't this tend to contradict what I said earlier about the way domestic dogs developed their deeper chest? Well, yes, to some extent. I'm guessing that early in the development of domestic dogs, they all developed greater stamina than wolves, and the deeper chests that go with greater stamina, but that the more generalized dogs branched off from this line of development before the elongated humerus of the sighthound began to develop. It's all just a guess. The bottom line remains, as evidenced in the photos, that most domestic dogs have deeper chests than most wild canids.

The other primitive dogs also often have the elbow joint lower than the chest. Here, what we are seeing is the retention of the primordial wolf characteristics in populations of dogs which were never subject to very much selective breeding. They retain the same proportions of chest depth and leg bone length as their gray wolf ancestors.

Fortunately, most primitive dogs are strikingly different from coyotes in other characteristics, especially color. Most "pariah" dogs tend to be yellow in color. Many also have drooping ears and/or curled tails, which coyotes and other wild canids never have.

The Australian dingo (Canis lupus dingo) has a wolf-like shallow chest that leaves its "elbow" at or below the underline of the chest. But besides the fact that it doesn't live where coyotes live, its color clearly distinguishes it from a coyote. Photo by Paleontour, licensed via Creative Commons license.		The Crete hound is a primitive dog (possibly Canis lupus dingo or C. l. familiaris) whose "elbow" is much lower than the underline of its chest, just like a coyote. However, its color, curled tail, and rose ears can only be those of a domestic dog. Photo by Astrid and Torsten, licensed under GNU Free Documentation License.
The Carolina dog (possibly Canis lupus dingo or C. l. familiaris) is another primitive dog whose "elbow" is at or below the underline of its chest. These "American dingoes" did live wild in places where coyotes now roam, but it is believed that all Carolina dogs have been taken into captivity. In any case, their color clearly distinguishes them from either wolves or coyotes. Photo by Flaxseedoil, Riverside Rescue, public domain.		The Canaan dog is a primitive dog (possibly Canis lupus dingo or C. l. familiaris) recently redomesticated from wild and semi-wild pariah dogs in Israel and surrounding countries. Its "elbow" lies just about in line with the underline of its chest, very much the same as a gray wolf. Again, like most primitive dogs, its color and its curled tail ensure that it will not be mistaken for a coyote. Photo by Matilda Holger, licensed under GNU Free Documentation License.

Next time you think you see a coyote, you know what to look for. Try to get a good view of the front legs and see where the "elbow" joint is. A domestic dog's elbow is higher than the bottom line of its chest, but a coyote has a very "leggy" look that comes from a shallow chest.

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