A mixed-breed dog (also called a mutt, crossbreed, mongrel, a bitsa, tyke, cur, or random-bred dog) is a dog that has characteristics of more than two breeds, or is a descendant of feral or pariah dog populations. The term "mutt" generally refers to a dog of unknown descent. Dogs interbreed freely, except where extreme variations in size exist, so mixed-breed dogs vary in size, shape, and color, making them hard to classify physically. Historically, all purebred dogs have been selectively bred from a mixed-breed population.

Terms for mixed-breed dogs

There is a profusion of words and phrases used for dogs that are not purebred. The words cur, tyke, and mongrel are generally viewed as derogatory in North America, whereas in the United Kingdom mongrel is the unique technical word for a mixed-breed dog, so is not a term of disparagement. Many American owners prefer mixed-breed. Mutt is also used (in the U.S.A and Canada), sometimes in an affectionate manner. In Hawaii, mixed breed dogs are referred to as poi dog, and in the Bahamas, they call them Pot Cakes (referring to the table-leftovers they are fed). Some American registries and dog clubs that accept mixed-breed dogs use the breed name All American, referring to the United States' reputation as a melting pot of different nationalities. In South Africa, the tongue-in cheek expression pavement special is sometimes used as a description for a mixed-breed dog. Random-bred dog, mutt, and mongrel are often used for dogs who result from breeding without the supervision or planning of humans, especially after several generations, whereas crossbreed implies mixes of known breeds, sometimes deliberately mated.

In Brazil and the Dominican Republic, the name for mixed-breed dogs is vira-lata (vira: to turn, to bring down; lata: tin can, trash can) because there are dogs without owners that feed on urban garbage on the streets, and often knock over trash cans to reach the food. Therefore, by having stray dogs it seems to increase the amount of "mixed-breed" dogs.

Slang terms are also common. Heinz 57 is often used for dogs of uncertain ancestry, in a playful reference to the "57 Varieties" slogan of the H. J. Heinz Company. In some countries, bitsa (or bitzer) is common, meaning "bits o' this, bits o' that". A fice or feist is a small mixed-breed dog. In Newfoundland, a smaller mixed-breed dog is known as a cracky, hence the expression "saucy as a cracky" for someone with a sharp tongue.

To complicate matters, many owners of crossbreed dogs identify them—often facetiously—by an invented breed name constructed from parts of their parents' breed names. For example, a cross between a Pekingese and a Poodle is called a Peekapoo, possibly a play on peek-a-boo, along with the Goldendoodle, a cross between a poodle and a golden retriever. As another example, one of the UK's Queen Elizabeth's famous Corgis mated with her sister's Dachshund, and the resulting offspring are referred to as Dorgis.

Appearance

All possible body shapes, ear types, and tail styles can appear in mixed breeds. Extremes in appearance, such as the flattened face of the Bulldog or the extremely curled tail of the Pug, seldom survive even the first crossbreeding. Mixed-breeds also tend to have a size between that of their parents.

Predicting the adult appearance of a mixed-breed puppy is difficult. Even purebred puppies do not look much like the adult dogs they will become, and with mixed-breed puppies it is nearly impossible. If one knows the breeds of the parents, some characteristics can be ruled out; for example, a cross between two small purebreds will not result in a dog the size of a Great Dane. Some breeds tend to pass on their physical traits to mixes more than others. Border Collies and some Spaniels, for example, often produce offspring with similar coats and ears. The crossbreed offspring of German Shepherds usually have Shepherd faces and other characteristics.

With each generation of indiscriminate mixing, the offspring move closer to the genetic norm. Dogs that are descended from many generations of mixes are typically light brown or black and weigh about 18 kg (40 lb). They typically stand between 38 and 57 cm (15 and 23 inches) tall at the withers.

Guessing a mixed-breed's unknown ancestry is difficult for even knowledgeable dog observers, because mixed breeds have much more genetic variation than among purebreds. For example, two black mixed-breed dogs might each have recessive genes that produce a blond coat and, therefore, produce offspring looking unlike their parents.

Health

The theory of hybrid vigor suggests that dogs of mixed ancestry will be healthier than their purebred counterparts. Mating dogs of very similar appearance over several generations have caused purebreds to carry many recessive homozygotic alleles, many of which are detrimental. This is especially true if the dogs are closely related. This inbreeding among purebreds has made many of them susceptible to various genetic health problems. Mixed-breed dogs are more genetically diverse due to the more random nature of mating. They are less likely to have certain genetic disorders because there is a decreased chance that both parents carry the same detrimental recessive alleles. Consequently, there is an increased chance in mixed-breed dogs that if a recessive detrimental allele is inherited from one parent, it will be masked by its healthier dominant allele from the other parent. For example, large dogs such as the German Shepherd Dog often suffer from hip dysplasia. Mating a German Shepherd, a breed known to have an increase incident of this disease, with a different purebred dog not known to suffer from it, reduces the likelihood that the cross-breed produced will suffer from hip dysplasia. It should be noted that mating two different purebreds in which both have an incident of the same genetic disease, the resulting cross-breed will usually have a similar chance of developing the genetic disease as inbreeding a purebred, but it may have a decreased probability of other genetic ailments that are not the same between the two different purebred parents. Overall, because of the effect of hybrid vigor in other species[1], it is often assumed that the same effect occurs in mixed-breed dogs. This would mean that on average, mixed-breed dogs are often healthier, have reduced incidents of genetic diseases, and live longer than their purebred parents.

Knowing the recent disease history is ultimately important in dog breeding. Breeding a Shepherd with another Shepherd in which the ancestors of both have no documented cases of genetic diseases will, with a high degree of certainty, give a healthy purebred. Another method to ensure a health dog would be to have the parental dogs genetically tested for a particular disease. This can be successful for diseases that have been identified to be caused by a single gene. Most often, this method can be difficult because the genetic determinant for many diseases have not been isolated, or the genetic determinant is caused by many genes, such as in hip dysplasia [2].

Some purebred dog breeds have difficulties due to the exaggerated physical traits associate with that breed. For example, the Bulldog has such small hips and such a large head that Caesarean sections are frequently, but not always, required to produce puppies.

There is no guarantee of good genetic health of any dog, purebred or otherwise, as not all damaging genes are recessive. Also, of course, purebred and mixed-breed dogs are equally susceptible to nongenetic ailments, such as rabies, distemper, injury, and infestation by parasites.

Types of mixed breeding

Recognized dog breeds are a result of human selection in that dogs were traditionally bred for specific functions. Most existing dog breeds began as mixed breeds, either by random occurrence or by deliberate crosses of existing breeds. Encouraging desirable traits and discouraging others, breeders sought to create their ideal appearance or behavior, or both, for dogs, and, additionally, to ensure that the dogs could consistently produce offspring with the same appearance or behavior.

Mixing breeds can lead to desirable results, especially in the hands of an expert breeder. On the other hand, inexperienced crossbreeders can produce disastrous results. For example, the offspring of an obsessive Border Collie and an energetic, destructive Terrier could be dogs whose behavior is so erratic that would make the dog a liability.

Mixed-breed dogs can be divided roughly into three types:

• Crossbreed dogs, which are mixtures of two recognized breeds. Dogs that result from two different purebred parents are known as crossbreeds. Some crossbreeds have traits that make them popular enough to be frequently bred deliberately, such as the Cockapoo—a cross between a Poodle and a Cocker Spaniel—and the Labradoodle, which crosses a Labrador Retriever with a Poodle. Other crossbreeds occur when breeders are hoping to create new breeds to add and reinforce characteristics from one breed into another breed. Most crossbreedings, however, occur accidentally.
• Mixes that show characteristics of two breeds or more breeds. A mix might have some purebred ancestors, or might come from a long line of mixed-breeds.
• The generic pariah dog, or feral Canis lupus familiaris, where non-selective breeding has occurred over many generations. The term originally referred to the wild dogs of India, but now refers to dogs belonging to or descended from a population of wild or feral dogs. The Canaan Dog is an example of a recognized breed with pariah ancestry. Pariah dogs tend to be yellow to light brown and of medium height and weight. This may represent the appearance of the modern dog's ancestor. DNA analysis has shown pariah dogs to have a more ancient gene pool than modern breeds.

There is no scientific justification for the belief that a purebred bitch is in any way tainted after mating with a dog of another breed. Future matings with dogs of the same breed will produce purebred puppies.

Mixed breeds in dog sports

Mixed-breed dogs can excel at dog sports, such as obedience, dog agility, flyball, and frisbee. Often, highly energetic mixed-breeds are left with shelters or rescue groups, where they are sought by owners with the caring, patience, and drive to train them for dog sports, turning unwanted dogs into healthy, mentally and physically stimulated award winners.

Until the early 1980s, mixed-breed dogs were usually excluded from obedience competitions. However, starting with the American Mixed Breed Obedience Registry (AMBOR) and the Mixed Breed Dog Club of America (MBDCA), which created obedience venues in which mixed-breed dogs could compete, more opportunities have opened up for all dogs in all dog sports. Most dog agility and flyball organizations have always allowed mixed-breed dogs to compete. Today, mixed breeds have proved their worth in many performance sports.

In conformation shows, where dogs' conformation is evaluated, mixed-breed dogs normally cannot compete. For purebred dogs, their physical characteristics are judged against a single breed standard. Mixed-breed dogs, however, are difficult to classify except according to height; there is tremendous variation in physical traits such as coat, skeletal structure, gait, ear set, eye shape and color, and so on. When conformation standards are applied to mixed-breed dogs, such as in events run by the MBDCA, the standards are usually general traits of health, soundness, symmetry, and personality. The Kennel Club (UK) operates a show called Scruffts (a name derived from its prestigious Crufts show) open only to mixed-breeds in which dogs are judged on character, health, and temperament.

Some kennel clubs, whose purpose is to promote purebred dogs, still exclude mixed breeds from their performance events. The AKC and the FCI are two such prominent organizations. However, the AKC does allow mixed breed dogs to earn their Canine Good Citizen award.

Advantages and drawbacks

The mature appearance and behavior of purebred puppies is more predictable than that of mixed breeds, including cross-breeds. With purebred dogs, the genetic variations are well documented and a breeder has a fair estimation of what type of offspring a given pair will produce. Still, there is variation within breeds; for example, two champion sheep-herding Border Collies might produce offspring with no interest in sheep herding.

Overall, mixed breed dogs tend to be healthier. They have more genetic variations than purebred dogs. Often, breeds can be associated with specific health problems. Breeding dogs who are prone to similar health problems greatly increases the chance of health problems in the offspring. By breeding dogs who are prone to different problems, the chances of serious health problems are lowered. Genetic variety increases the chances of good health. Some trainers believe mixed-breeds exhibit higher average intelligence than purebreds, but others believe mixes are no more intelligent than purebreds. Both sets feature both slow learners and dogs with high learning capacity. For example, Benji, the hero in a series of films named for him, was a mixed-breed terrier. It may be more difficult to predict the trainability of mixed-breed dogs when they are very young. Most Golden Retrievers are eager to please, but a cross of a Golden with the independent Siberian Husky could inherit either dog's trainability—or could result in a dog with the endurance and athleticism of the Siberian and the trainability of the Golden.

Many people enjoy owning mixed breeds, valuing their unique appearance and characteristics; while purebred dogs exhibit little variability of appearance within their breed, mixed-breed dogs exhibit often unique appearances. Although some dog owners prefer the status of owning a specific breed of dog or have a nostalgic attachment to a breed they wish to acquire, many others enjoy mixed-breed dogs that exhibit characteristics similar to their favorite breeds; in fact, with a mixed-breed, they can enjoy some aspects of appearance and personality of two favorite breeds with a single dog. There is usually an abundant supply of mixed-breed dogs wanting owners, available at negligible prices, while pedigreed dogs can cost hundreds or thousands of dollars and reputable breeders can be hard to find.

Some owners value a dog's pedigree as a status symbol and, therefore, have no use for mixed-breed dogs; others particularly appreciate the physical or behavioral traits of certain breeds; still others ignore pedigree and, instead, value a dog's personality and health. In short, most dog owners believe that their dog's breed—and specifically their own dog—is the best sort of dog there is.

Local animal shelters adopt out dogs of both purebred and mixed ancestry, emphasizing each dog's personality and suitability as a companion for each potential owner's lifestyle.

See also

• Hybrid vigor
• Dog hybrids and crossbreeds

References