August excerpt: What Is a Dog?

August 26, 2016


“Why Do Village Dogs All Look Alike?”*

Of the billion dogs in the world, three-quarters of them look as much alike as do the individuals of any other species.

A few years ago we asked a Navajo shepherd what a Navajo sheepdog looked like. He said, “A Navajo sheepdog is not too big and not too small.” To us the Navajo sheepdogs were identical in size and shape and color variations with the sheepdogs of Sonora and the village dogs in the mountains of Venezuela or the ones we worked with in eastern and South Africa or saw in India and China.

That is true of the majority of dogs in the world—they are not too big and they are not too small. One of the most fascinating details about that 85 percent of the dogs in the world that control their own reproductive life is: they all look alike.

The similarity between the pigeon world and dog world continues. Pigeons, in some sense, all look alike. The pigeons in the Mexico City dump fly and look just like the pigeons in Trafalgar Square, like the pigeons in Istanbul, like the pigeons in Central Park, like the pigeons in Milan. Wherever you go, the pigeons in the park look like the pigeons in every other park.

No two pigeons are the same, of course. No two pigeons are exactly the same color or size or shape. At the same time, they all look pigeon-like. They have an essence that evokes pigeons. “I know one when I see one.”

It is true for every species. The chickadees at our feeders all look very much alike, and it takes practice to see the little differences that distinguish them. They all can get into the bottle feeder as far as we know. The same is true with blue jays and squirrels. The squirrels are intriguing because around here you sometimes see a black one or a brown one, but it still looks like a squirrel. At one time we lived on a small island of nesting seagulls. After a few years, we could distinguish the boys from the girls because of subtle differences in their head shapes.

All wolves look alike. But the wolves also show small variations of a neutral monotone. It could be that wolves vary more in coat color than squirrels do. Thus, a pack of grey wolves (Canis lupis) might have mostly gray animals except for an anomalous white one or black one. In some regions, the wolves are mostly white. Right now there seems to be an increase in frequency of black wolves in Yellowstone National Park. Color variations appear in certain subspecies of the gray wolf: the red wolf (Canis lupus rufus), the Arctic wolf (Canis lupus arctos), and the Mexican wolf (Canis lupus baileyi). Yet even with a color difference, they still look like wolves. (Taxonomists are confused about which scientific name to give to some of these wolves, but they recognize the essence of wolf in all the variations.)

In any given area, the wolves tend to be the same size. From the far north to the east of the Mediterranean, they will grade in size from larger to smaller. A biologist would say this gradation is a cline, that the species follows Bergmann’s rule: it grades from a large animal in the north to a smaller size on the equator. Ecologist Val Geist once pointed out that the cline isn’t always perfect. Wild sheep also exhibit these clines. For example, the bighorn sheep (140–300 pounds, 3–3.5 feet) of the northern Canadian Rocky Mountains grade down to the smaller mouflon of the Iranian desert (90–120 pounds, up to 2–4 feet at shoulder height) with smooth coats. What’s noteworthy is that all those different “species” of sheep along the cline are interfertile from north to south—including domestic sheep. As with the dogs, the spot on the cline from which the domestic sheep evolved is difficult to pinpoint. The big gray wolves in the north are interfertile with all the other members of the genus, all the way to little jackals in equatorial Africa. The genus Canis appears to us to be a single species cline.

Free-ranging street and village dogs, also, tend to be bigger regionally in the north and up into the mountains, and smaller in equatorial regions. In Greenland, on Baffin Island, and over in the Hudson Bay area, the village dogs we have observed can weigh as much as sixty pounds, whereas equatorial dogs are basenji-like and weigh less than twenty-five pounds. With increasing latitude and altitude, dogs tend toward being rough coated.

So, if the village dogs range from twenty to sixty pounds and from smooth coats to rough, how could we say they all look alike? It is a good question. For us, the population density of dogs weighs heavily on our thinking. The farther you get from the equator, or the higher in the mountains, the fewer the street or village dogs. In the warm climates, the density can be substantial. When we want to study village dogs, our preference is to go south (toward the equator) rather than north. Those regional warm-weather dogs, all about the thirty-pound, lion-colored variety, are usually prevalent. This strongly indicates that the overall size and color of the local dog is an adaptation to the local geography, the climate, and the prey base—in other words, the niche in which they make their living.

Every once in a while we will see a report that scientists have discovered a new species of mammal. That means they have discovered a new shape in a population of animals that are sexually isolated from all other species (well, maybe sexually isolated, but not always). They name it with a Latin binomial indicating the genus and species. It might not be a bad system if the biologists stuck to the rules. many people contend that dogs and wolves are in the same species (Canis lupus lupus). The classification of any species should be mostly about biology/evolution but it can also be about beliefs, culture, politics, and numerous other factors. When a wild canid was first discovered in New Hampshire in 1944, after a lot of talk and measurements it was a classified as a coyote (Canis latran). The animals were bigger than the well-known western coyote (also of course Canis latrans). Barbara Lawrence and William Bossert at Harvard measured skulls of wolves, coyotes, and the New England canid and concluded that the New England animal was, although not exactly the same as the coyotes, closer physically to them than to wolves. Well, those of us who had studied with Professor Wood did not believe skull measurements to be accurate indicators of species, and our research, done later with our student, Michael Sands, revealed histologically (shape) that the sweat glands in their feet resembled those of gray wolves in Alaska and not those of western coyotes, although few people seem ever to have read that paper, published in the Journal of Mammalogy in 1976.

It was always suspicious that had the New England canid been classified as a gray wolf it would have fallen under the Endangered Species Act. That would have led to any number of management restrictions about how fish and game scientists in New England states could manage this population. We now have lots of these wild canids in this region. The discussion is heating up as the U.S. Fish and Wildlife Service decides whether it is time to take the gray wolf off the Endangered Species list because its population is increasing. If the eastern coyote really is a gray wolf, then it is not rare and not endangered. Again it looks like whatever species it is, the discussion is more political than scientific.

Interested people have debated the ancestry of the dog since the late 1800s. Not only have wolves, jackals, or dingoes been suggested as an ancestor of dogs, but several people argued that dogs were the result of hybridization between wolves and jackals. There were astonishing theories about big dogs (breeds) evolving from the Chinese wolves. The Nobel Prize–winner Konrad Lorenz at one point suggested that some “breeds” of dogs descended from wolves and others from golden jackals. When we met him in 1978, he started the conversation by saying, “Everything I have written about the dog is wrong—but it was better that I discovered it rather than someone else.”

*This excerpt has been adapted (without endnotes) from What Is a Dog? by Raymond Coppinger and Lorna Coppinger (2016).


To read more about What Is a Dog?, click here.

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