Mixed-breed dog

A healthy mixed-breed dog shows hybrid vigor.

A mixed-breed dog is a dog whose ancestry is generally unknown and that has characteristics of two or more types of breeds, or is a descendant of feral or pariah dog populations. "Random-breed" is a genetic term meaning an animal, population, or breed that was bred or developed without planned intervention of humans; and whose ancestry and genetic makeup is generally not known.

Mixed-breeds

The descriptive term mixed-breed is technically a misnomer. The idea that such dogs are a mix of defined breeds stems from an inverted understanding of the origins of dog breeds. Pure breeds have been, for the most part, artificially created from random-bred populations by human selective breeding with the purpose of enhancing desired physical or temperamental characteristics. Dogs that are not purebred are not necessarily a mix of such defined breeds.^[1]

In contrast, the term crossbreed refers to dogs produced by the intentional crossing of two different known purebred dog breeds. Dogs interbreed freely, except where extreme variations in size exist, so mixed-breed dogs vary in size, shape, and color, making them difficult to classify physically.

Terms for mixed-breed dogs

A mixed-breed with collie-whippet characteristics.

There is a profusion of words and phrases used to describe dogs that are not designated as a purebred or pedigreed dog. The words cur, tyke, mutt, and mongrel are used, sometimes in a derogatory manner. There are also regional terms for mixed-breed dogs. In the United Kingdom mongrel is the unique technical word for a mixed-breed dog. North Americans generally prefer the term mix or mixed-breed. Mutt is also commonly used (in the U.S.A and Canada), often in an affectionate manner. Some American registries and dog clubs that accept mixed-breed dogs use the breed description All American. In the rural southern United States, a small hunting dog is known as a feist.

There are also names for mixed-breeds based on geography, behavior, or food. In Hawaii, mixes are referred to as poi dogs, and in The Bahamas, the common term term is potcakes (referring to the table-leftovers they are fed). In South Africa the tongue-in-cheek expression pavement special is sometimes used as a description for a mixed-breed dog. In the Philippines, they are often called "askals", a Tagalog-derived contraction of "asong kalye" or street dog.

Slang terms are also common. Heinz 57 or Heinz 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, such as Australia, bitsa (or bitzer) is common, meaning "bits o' this, bits o' that". In Brazil and the Dominican Republic, the name for mixed-breed dogs is vira-lata (trash-can tipper) because of homeless dogs who knock over trash cans to reach discarded food. In Newfoundland, a smaller mixed-breed dog is known as a cracky, hence the colloquial expression "saucy as a cracky" for someone with a sharp tongue.

Scientists and scholars usually use the terms mongrel, mixed-breed, or random-bred dog for dogs born of breedings not supervised or deliberately planned by humans. The term crossbreed is used to describe mixes of known breeds, sometimes deliberately mated.

Appearance

This cross between a German Shepherd and a Golden Retriever has traits of both parents

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.

Determining ancestry

These littermates share an Australian Shepherd mother, although neither greatly resembles that breed.

Guessing a mixed-breed's 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.

Starting in 2007, blood samples^[2] and cheek swabs^[3] have become available to the public. The companies claim their DNA-based diagnostic test that can genetically determine the breed composition of mixed-breed dogs. These tests are still limited in scope because only a small number of the hundreds of dog breeds have been validated against the tests, and because the same breed in different geographical areas could have different genetic profiles. Also, the tests do not test for breed purity, but for genetic sequences that are common to certain breeds. With a mixed-breed dog, the test is not proof of purebred ancestry, but rather an indication that those dogs share common ancestry with certain purebreds.

Health

A healthy mixed-breed with shiny coat and bright eyes.

The theory of hybrid vigor suggests that as a group, dogs of varied ancestry will be healthier than their purebred counterparts. In purebred dogs, intentionally breeding dogs of very similar appearance over several generations produces animals that carry many of the same alleles, some of which are detrimental. This is especially true if the dogs are closely related. This inbreeding among purebreds has exposed various genetic health problems not readily apparent in less uniform populations. Mixed-breed dogs are more genetically diverse due to the more haphazard nature of their parents' mating. "Haphazard" is not the same as "random" to a geneticist. The offspring of such matings are less likely to express certain genetic disorders because there is a decreased chance that both parents carry the same detrimental recessive alleles. However, some deleterious recessives are common across many seemingly unrelated breeds, and therefore merely mixing breeds is no guarantee of genetic health.

In fact, crossbreeding two poor specimens together does not guarantee the resulting offspring will be healthier than the parents because the offspring could inherit the worst traits of both parents. This is commonly seen in dogs from puppy mills. Healthy traits have been lost in many purebred dogs lines because many breeders of showdogs are more interested in conformation - the physical attributes of the dogs in relation to the breed standard - than in the health and working temperament for which the dog was originally bred.

Purebred and mixed-breed dogs are equally susceptible to non-genetic ailments, such as rabies, distemper, injury, and infestation by parasites.

Several studies have shown that mixed-breed dogs have a health advantage. A German study finds that "Mongrels require less veterinary treatment".^[4] Studies in Sweden have found that "Mongrel dogs are less prone to many diseases than the average purebred dog"^[5] and, referring to death rates, “Mongrels were consistently in the low risk category”.^[6]

In one landmark study, the effect of breed on longevity in the pet dog was analyzed using mortality data from 23,535 pet dogs. The data was obtained from North American veterinary teaching hospitals. The median age at death was determined for pure and mixed breed dogs of different body weights. Within each body weight category, the median age at death was lower for pure breed dogs compared with mixed breed dogs. The median age at death was "8.5 years for all mixed breed dogs, and 6.7 years for all pure breed dogs" in the study.^[7]

A 2003 study in Denmark also found "Higher average longevity of mixed-breed dogs (grouped together).^[8]

Types of mixed-breeding

Most dog breeds are a result of human selection. Existing dog breeds began as mixed-breeds, either random-bred 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.

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

The generic pariah dog is believed to resemble the body form and appearance of the ancestral Canis lupus familiaris from which other dog breeds were derived.

• Mixes that show characteristics of two or more breeds. A mix might have some purebred ancestors, or might come from a long line of mixed-breeds. These dogs are usually identified by the breed they most resemble, such as a "Lab mix" or "Collie-Shepherd", even if their ancestry is unknown.
• 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.
• Functional breeds, which are purpose-bred, pedigreed dogs whose ancestors are not purebred, but rather are selected by their performance at a particular tasks. Examples of this are the Alaskan Husky, the Eurohound, and the Pointer/Greyhound mixes referred to as Greysters, which compete at skijoring and pulka races, particularly in Europe. The distinction between a "mix" and a "breed" is less distinct in these cases, and occasionally a functional breed such as this becomes accepted as a breed over time.
• Crossbreed dogs, which are mixtures of two recognized breeds. Dogs that result from two different purebred parents are known as crossbreeds. Some crossbreeds have become popular enough to be frequently bred deliberately, such as the Cockapoo—a cross between a Poodle and a Cocker Spaniel. Other crossbreeds occur when breeders attempt to add and reinforce characteristics from one breed into another breed.

Purebred dogs are known by breed names given to groups of dogs that are visibly similar in most characteristics and have reliable documented descent. But to complicate matters, many owners and breeders of crossbreed dogs identify them—often facetiously— by invented breed names constructed from parts of their parents' breed names. These are known as portmanteau names. For example, a cross between a Pekingese and a Poodle is often referred to as a Peekapoo. Another popular cross is the Goldendoodle, a cross between a poodle and a golden retriever. As another example, one of the UK's Queen Elizabeth II's famous Corgis mated with her sister's Dachshund, and the resulting offspring were referred to as Dorgis.

Mixed-breeds in dog sports

A mixed-breed dog demonstrates dog agility.

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 Clubs 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 to a breed standard 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. While the AKC does allow mixed-breed dogs to earn their Canine Good Citizen award, mixed-breed dogs are not permitted to enter AKC "all breed" events.

Advantages and drawbacks

The mature appearance and behavior of purebred puppies may be more predictable than that of mixed-breeds, including cross-breeds. With purebred dogs, genetic variations are well documented and a reputable 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.

Two mixed-breed dogs from Central America.

A dingo illustrated alongside a Hare Indian dog. The dingo is currently under threat from crossbreeding, while the latter is now completely extinct because of it

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.

Studies that have been done in the area of health show that mixed-breeds on average are both healthier and longer-lived than their purebred cousins. This is because current accepted breeding practices within the pedigreed community results in a reduction in genetic diversity, and can result in physical characteristics that lead to health issues.^[9][10]

Studies have shown that cross-bred dogs have a number of desirable reproductive traits. Scott and Fuller^[11] found that cross-bred dogs were superior mothers compared to purebred mothers, producing more milk and giving better care. These advantages led to a decreased mortality in the offspring of cross-bred dogs.

Not all dog owners appreciate mixed-breed dogs. Some owners value a dog's pedigree as a status symbol and, therefore, have no use for mixed-breed dogs; others appreciate or have an emotional attachment to the physical or behavioral traits of certain breeds; still others erroneously believe that a pedigree means a dog will have superior personality traits and health.

While purebred dogs exhibit little variability of appearance within their breed, mixed-breed dogs often exhibit unique appearances. People who enjoy mixed-breeds, often value their one-of-a-kind appearance and characteristics. 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
• Pariah dog

Links

• The Canine Diversity Project
• Mixed Breed Dogs from dogsindepth.com

References