Until very recently, the amount of variation in the domestic dog was sufficient to maintain genetic health. Multiple domestications and back-crossings with wolves have meant that dogs worldwide still have an estimated 95 percent of the variation that was present in the wolves during the time of domestication. Most of this variation lives on today in street dogs and mongrels, but pedigree dogs have lost a further 35 percent. That may not seem like much, but let’s imagine the scenario in human terms. Mongrels maintain levels of variability that are similar to those found globally in our own species. In many individual breeds, however, the amount of variation within the whole breed amounts to little more than is typical of first cousins in our own species. And we humans know that repeated marriages between cousins eventually lead to the emergence of a wide range of genetic abnormalities—which is why marriages between close relatives are taboo in most societies. It is astonishing that the same consideration has not been given to dogs.
Just a handful of prize-winning popular sires are used to father the majority of puppies. This has tremendously restricted the gene pool. For example, about eight thousand new golden retrievers are registered in the UK each year, with a total population of perhaps a hundred thousand. Over just the last six generations, inbreeding has removed more than 90 percent of the variation that once characterized the breed.1 In a recent sampling of the Y (male) chromosomes of dogs in California, no variation at all was found in fifteen out of fifty breeds, indicating that most of the male ancestors of each and every dog in those breeds had been close relatives of each other.2 Some of the other breeds surveyed had only a very little variation. In the context of the imported breeds in the study—such as the Rhodesian ridgeback, the boxer, the golden retriever, the Yorkshire terrier, the chow chow, the borzoi, and the English springer spaniel, this is not surprising. Assuming that all Californian examples are likely descended from a small founder population, limited gene pools are to be expected; much more variability might have been apparent if the samples had been taken in other countries. Of more concern was the lack of variation in the three American breeds being studied, since these are more likely to be representative of those breeds worldwide. There was no variability at all in the fifteen Boston terriers tested, and only a small amount in the twenty-six American cocker spaniels and ten Newfoundlands. Conversely, a couple of breeds recently derived from street dogs, the Africanis (or Bantu dog) and the Canaan dog, showed levels of variation similar to those in mongrels—but this is the result of a deliberate policy among their breeders, who have seen the problems that popular sires have brought to other breeds of minority interest.
The inbreeding of dogs—though utterly deleterious to them—is potentially a huge boon to mankind. The canine genome was chosen by geneticists as one of the first to be sequenced, precisely because the occurrence of so many inherited diseases in today’s pedigree dogs provides scientists with abundant opportunities to study, and then devise cures for, their (much rarer) counterparts in humans. The gigantic, if unintended, global experiment that is modern pedigree dog breeding promises to bring cures for many of our own diseases—and many years sooner than if the research had had to be conducted in mice or other laboratory animals. This will undoubtedly benefit our own species, but what about the dogs? If they could grasp the implications of what we’ve done to them, what would our dogs have to say?
The effects of selection for extreme shapes, sizes, and conformations of dogs have been causing concern for more than two decades, on both sides of the Atlantic.3 Even earlier than that, it had become apparent that the previously working origins of most breeds had been overwhelmed by the seemingly arbitrary demands of the show ring. Since then, as a result of defects due to the slavish application of breed standards, many breeds have become caricatures by comparison with their former appearance. Other problems, too, have emerged as a consequence of such breeding for extremes. For example, puppies of many of the round-headed breeds, such as bulldogs, pugs, pekes, and Boston terriers, have to be born by Cesarean section because their heads are too big for a natural birth. By 2009, when a high-profile documentary on BBC television—“Pedigree Dogs Exposed”—raised the issue again in the UK, the extent of the suffering caused by selective breeding had become better documented.4 (This issue has received less public airing in the United States, but that’s not to say that the extent of such problems is any less there than in the UK.) Responsibility for selective breeding and its consequences must rest squarely with the breed clubs that control it.
Together, the breed clubs control a large proportion of the canine genome in the United Kingdom and the United States. (This is true in most other Western countries as well.) The competition is mainly between a few “top breeders” within each breed, regulated by judges who are (or were) themselves “top breeders.” Selective breeding toward the latest interpretation of the “breed standard” leads to a variety of welfare outcomes that affect more and more dogs of that breed—not just those that become champions but also many dogs destined to become pets. The UK Kennel Club publishes breed standards that are available to help prospective dog owners find breeds that suit their lifestyle. For example, they describe one popular companion breed, the Cavalier King Charles spaniel, thus: “Characteristics: Sporting, affectionate, absolutely fearless. Temperament: Gay, friendly, non-aggressive; no tendency to nervousness.” No mention here that the whole of the modern breed is probably descended from just six individuals, and that the breed is prone not only to heart problems but—more importantly, if you’re one of these dogs—to cysts on the spinal cord that cause “phantom” pains that the dog’s behavior clearly shows are very distressing.5
The various reports on the effects of inbreeding catalogue a wide range of insults to the welfare of dogs of particular breeds. They can be divided into two broad types. First, some are side effects of deliberate breeding for exaggerated characteristics: The problems of puppies with large heads that won’t fit through the bitch’s birth canal have already been mentioned. Likewise, “cute” folded skin on the face increases the risk of dermatitis, the legs of the most fine-boned toy breeds are prone to painful fractures that can occur during normal canine behavior such as jumping, and so on.
Second, the extreme levels of inbreeding (what those in the business refer to as “line-breeding”) have caused many heritable diseases to emerge in numerous breeds. These diseases are becoming widely documented, and although the genetic mechanisms behind them can be complex, most essentially arise because of accidental overbreeding from dogs that are carriers of a defective version of a gene. Usually, because they are only carriers, they are not themselves affected, and so the problem goes undetected until their descendants are mated together, producing some puppies with two defective copies of the same gene. Progressive retinal atrophy (an eye disease) in Cardigan Welsh corgis is a well-documented example, as is “rage syndrome” (episodic dyscontrol) in English cocker spaniels. Modern DNA technology, though expensive, has the potential to at least stop the spread of inherited disease—specifically, through its ability to detect carriers that have no outward signs of the disease as well as defects that do not become obvious until later in life, when the dog has already been bred from.
Other disorders are inherited in more complex ways, through interactions between many genes, but the general principle is the same. One common defect in many medium- and large-sized breeds is hip dysplasia, caused by loose ligaments around the hip joint—a condition that leads to pain, restriction of movement, and lameness. In some breeds there are enough individuals with “good hip genes” that preventing dogs with poor hips from breeding might eventually remove the defect from the breed. In others, such as the golden retriever, the main factor determining whether the hips fail turns out to be how the dog is exercised when young; in other words, virtually all members of this breed have the genetic potential to develop hip dysplasia, and therefore it cannot realistically be “bred out” unless the rules of pedigree are broken.
Correct
ing genetic defects within breeds is bound to be difficult. Removing all individuals affected by one defect from the breeding pool inevitably reduces the genetic variation within the breed, causing other defects to appear or become more prevalent. It’s generally thought that such outbreeding is truly effective only when several different strains coexist within a breed, as with show- and working-dog lines—and there may be resistance to this from their respective enthusiasts. The obvious solution, of course, is to open up the closed gene pools of the existing breeds by crossbreeding—merging several breeds into one, or creating new ones by crossing two or more distantly related breeds.6 Paradoxically, although both of these ideas meet with strong resistance from today’s breeders, they were the very mechanisms by which the nineteenth-century dog enthusiasts generated today’s breeds!
With hindsight, it was inevitable that the shift in emphasis in dog breeding from function to appearance would be damaging to dog welfare. Wild animals, including wolves, are selected by the environment within which they live: a case of “survival of the fittest.” Once one species becomes totally dependent upon another, as happened to dogs thousands of years ago, natural selection becomes relaxed in some areas. Dogs who perform arduous tasks, such as sheepdogs, have to stay fit and healthy above all else, and so their breeders are unlikely to select for traits that seriously impair welfare—hence the reluctance of many of the working-dog breed clubs to have anything to do with the show lines. In dogs bred for showing, deficiencies in fitness can be compensated for, by their owners and through veterinary intervention. Provided they do not affect performance in the show-ring, welfare problems can spread through a breed—problems due to deliberate selection for appearance as well as those that arise by accident through inbreeding. While most breed organizations make attempts to halt this process (and some have tried to reverse it), the evidence that such efforts have been largely unsuccessful in the past is there in the dogs themselves.
Selective breeding has also damaged dogs’ abilities to communicate with each other. Since communication is crucial to harmonious social interaction, dogs whose repertoire of visual signals is restricted are essentially penalized. Those whose intentions cannot easily be gauged are often avoided by other dogs. Others, having been on the receiving end of unexpected aggression because they could not read another dog’s intentions, become anxious toward all other dogs.
Indeed, the structures that the wolf uses for visual signaling have been drastically altered by the extremes of body conformation introduced by selective breeding. Jaws have been shortened, facial expressions hidden by loose skin or obscuring hair, ears permanently pricked up or hanging heavily, coats lengthened or made wiry so that hackles cannot be raised, legs shortened so that the dog cannot easily crouch, tails curled or docked. These changes have had a devastating effect on the visual signaling repertoire of many breeds; some, such as the Cavalier King Charles spaniel, seem incapable of emitting any of the wolf’s visual signals (which number over twenty, at a conservative estimate). Thus they no longer have access to the primary mode by which pack members can communicate with one another.
Many other breeds fare little better. In an attempt to quantify the effects of domestication on the ability to communicate, my colleagues and I performed a study comparing the visual signaling repertoires of a whole range of breeds, from the least to the most wolf-like—that is, from Cavalier King Charles to Siberian husky.7
Not surprisingly, the huskies were rated as the most wolf-like dogs in appearance, with a range of signals to match. In fact, their repertoire is essentially the same as the wolf’s, probably retained to allow precise communication within groups kept as sled teams. Medium-sized gundog breeds such as Labrador and golden retrievers, as well as the Munsterlander, retain between half and two-thirds of the wolf’s repertoire. So does the German shepherd, which has been deliberately bred to look like a wolf but not to behave like one. These breeds retain a common set of signals that permit a fair range of visual communication, albeit not as sophisticated as the wolf’s (see the box titled “Canine Body-Language”).
The number of wolf-like visual signals performed by each breed, and how wolf-like that breed is in general appearance (ranging from “not at all” on the left to “very similar” on the right).
The smaller breeds in the study, from cocker spaniel down to Cavalier King Charles, performed very few discernible visual signals. The Cavaliers’ only “signal” was to push another dog out of the way—the universal language of shove, not really a signal as such. And if need be, they could back this up with a growl. Even more intriguing was the finding that the signals performed by the four breeds with the smallest repertoires—Cavaliers, Norfolk terriers, French bulldogs, and Shetland sheepdogs—were almost invariably those that appear earliest in growing wolf cubs, such as muzzle licking and looking away. These breeds are arrested not only in terms of growth patterns but also in terms of the development of their ability to communicate in a wolf-like way. Although this study cannot be considered definitive, inasmuch as only a small proportion of breeds was sampled, it appears that breeds have been derived by arresting the wolf’s physical development—and are therefore, inevitably, smaller-than-average dogs—are handicapped by having the communicative abilities of a wolf cub. In addition to this general trend, more specific losses have occurred in breeds of all sizes: For example, the French bulldog’s short coat, which prevents it from effectively raising its hackles, is also a feature of much larger breeds such as Weimaraners.
Canine Body-Language
Dog ownership can be made much richer and more rewarding by an indepth understanding of how dogs signal to one another. This process would be much more straightforward if dogs all looked roughly the same, but fortunately there is a common underlying language that enables both dogs and people to understand canine moods and intentions.
First of all, the dog’s overall posture is a good indicator of its level of confidence. Dogs who are worried about the outcome of an encounter will tend to keep their body low to the ground, trying to look as unthreatening as possible, until they can be sure that the other dog means them no harm. A confident dog will stand tall.
Likewise, the lower the tail, the less confident the dog; dogs in retreat will usually tuck their tail forward between their hind legs. Precisely where “low” is will vary from one dog to another, because selective breeding has affected where the normal, relaxed tail position is in relation to the horizontal: Compare, for example, the tail position of a spitz dog (naturally curved and upright) with that of a greyhound (naturally low and straight). It’s the change in position that signifies the change in intention. An upright tail with a wagging tip indicates interest; a relaxed tail that’s being wagged from side to side using movement of the whole back end of the dog indicates excitement and/or a desire to play. Some dogs perform an exaggerated slow swish of their tails when they are contemplating aggression.
Moving toward the front of the dog, we find that the shape of its back can also be a giveaway. If rigid, it can indicate a low level of fear or anxiety, although some breeds have naturally stiff backs. A rounded-up back may indicate indecision—the dog looks as though her back legs are trying to move forward while her front legs are trying to stand still.
Ears are easy to read in some dogs, harder in others; but even in breeds with rather rigid ears the muscles at the base of the ear may show what the dog is trying to say. Ears pricked forward suggest alertness and interest; ears pulled back indicate anxiety and, if flattened as well, fear and an intention to withdraw. Tense eyebrows, often extending to the face overall, indicate threat, often accompanied by a fixed stare. In some dogs, this tension will also result in the whites of the eyes becoming (more) visible. A dog wishing to dissociate from an interaction will look away, often turning his head away so that it is at a rightangle to the other’s. Relaxed dogs will hold their mouth loose and slightly open when interacting with other dogs; tense dogs will hold their mouth shut tight. Fear and anger alike ca
n lead to the teeth being bared; the rest of the dog’s body-language, from the ears backward, should provide clues as to which of these two very different emotional states is applicable. The friendly “grin” or “smile,” with teeth slightly bared, is the position of the mouth in the affiliation display, though many dogs will use it as a signal in its own right when interacting with people—presumably because it has been rewarded by extra attention due to its superficial similarity to a human “smile.” The “cute” head-onside posture is likewise not a species-typical canid signal but, rather, a posture that—as some dogs have learned—evokes a rewarding response from their owner.
Because so many dogs can no longer perform the full repertoire of canid behavior, it isn’t always easy for dogs of different breeds to understand one another when they first meet. By deleting and distorting the wolf’s range of signaling structures through breeding, we have messed around with the dog’s visual communication system to the point where it just doesn’t work as well as it should.
Consider, for example, docked or immobile tails. Some breeds, such as bulldogs, have been bred to have very stiff tails that don’t wag particularly easily. In many others, such as spaniels, it’s traditional to amputate part or most of the tail, ostensibly to reduce the risk of injury. Docked tails are harder to see than entire tails, so dogs whose tails have been docked find it more difficult to communicate than dogs whose tails have been left as they should be. In 2008, researchers studied the impact of docking on communication by using a robotic model of a dog whose “tail” could be made to wag by remote control.8 After setting up the robot in off-leash exercise areas, they noticed that when its tail was wagging other dogs would approach it playfully whereas when the tail was upright and motionless other dogs avoided it. These reactions are consistent with what we already know about the use of the tail in signaling. Then the scientists replaced the long tail with a docked version. When the shorttailed robot was let loose in the park, other dogs approached it warily whether the tail was wagging or not—as if they couldn’t make up their minds how they were likely to be received. Although a real dog with a docked tail could probably overcome this shortcoming with other aspects of its body-language, the study clearly shows that tail docking puts dogs at a disadvantage when interacting with their own kind. At the very least, they would feel anxious when encountering one another for the first time; at worst, miscommunication could lead to unintended aggression.
Dog Sense Page 31
