A dog hybrid, also known as a crossbred dog or designer dog, is an individual dog with ancestry in two different purebred dog breeds. Designer dogs are described by portmanteau words, such as cockapoo. The term dog hybrids may describe first generation crosses from two purebred breeds, or any of various backcrosses, or the result of breeding successive generations of crosses in order to create a new breed of purebred dog, such as the Alsatian Shepalute, or outcrosses of any of those; the term dog hybrid does not have a consistent meaning.
In biology, the word hybrid has multiple meanings. One meaning refers to the result of interbreeding between two animals (or plants) of different species, such as a mule (Equus caballus + Equus asinus) or in a cross between a lion and a tiger, known as interspecific hybrids. Interspecific hybrids are often (although not always) sterile.
The offspring resulting from breeding within the same species, but from two distinct populations, is known as an intra-specific hybrid. This second meaning is often used in plant breeding..
Dogs and wolves were once classified as separate species (Canis familiaris and C. lupus, respectively), so a wolf-dog cross was called a canid hybrid (interspecific). The domestic dog has been more recently reclassified as C. lupus familiaris, a subspecies of the wolf, and a wolf-dog cross (an example of an intra-specific hybrid) is commonly called a wolfdog.  Some fanciers continue to call wolf and dog crosses (and their descendants) wolf-dog hybrids.
A crossbreed or crossbred usually refers to an animal with purebred parents of two different breeds, varieties, or populations, usually deliberately bred for some purpose. A crossbred dog differs in this way from a mixed breed dog (also called random-bred or mutt) which has unknown or complex ancestry.
In crossbred dogs, because some traits are dominant, breeds tend to pass on some physical characteristics to crosses more than others. Border Collies and some Spaniels, for example, often produce offspring with similar coats and ears. The crossbred offspring of German Shepherds often have Shepherd faces and other characteristics. Crossbred dogs may vary in which characteristics of their purebred parents that they inherit, even within the same litter of puppies.
The Encyclopædia Britannica traces the term "designer dog" to the late 20th century, when breeders began to cross purebred poodles with other purebred breeds in order to obtain a dog with the poodles' hypoallergenic coat, along with various desirable characteristics from other breeds.
The connotation of the term "designer dog" is that the breeding is by design, between a deliberately chosen sire and dam, as opposed to an accidental breeding. Some breeders have taken this a step further, breeding a specific crossbreed to others of the same cross, setting a standard, and documenting the ancestry of puppies so bred over generations, in order to create a new breed of dog.
The primary identifying mark of a designer dog is that the resulting crossbred puppies are described with a portmanteau word made up of syllables (or sounds) from the breed names of the two purebred parents, such as schnoodle (Schnauzer and poodle cross). Other purebred breeds are being crossed to provide designer dogs described with a wide range of whimsical labels, such as the ShiChi (Shitzu and Chihuahua cross), the Chiweenie (Chihuahua and Dachshund cross), the Afador (Afghan Hound-Labrador Retriever cross), and even complex hybrids (with multiple breeds in recent ancestry) are being labeled in this manner, such as German Chusky (German Shepherd Dog, Husky, Chow Chow).
Specific designer dog name labels are popular because some percentage of designer dogs with the same breed ancestry will look similar to each other, even though hybridization does not result in as uniform a phenotype as the breeding of purebreds. The labels are useful to breeders in the marketing of puppies, and in the creation of affinity groups and clubs for owners of the designer dogs.
Another defining characteristic of designer dogs is that they are bred as companions and pets. Working and hunting dogs deliberately crossbred for a particular working purpose are not given portmanteau names; they are most often referred to by a type (not breed) name, such as Eurohounds (racing sled dogs) or Lurchers (hunting dogs.)
Although designer dogs are often celebrated for their novelty, an underlying motive for hybridization is an attempt to reduce the incidence of certain hereditary problems found in the purebred breeds used for the cross, while retaining their more appealing traits. Jon Mooallem in the New York Times writes, "Given the roughly 350 inherited disorders littering the dog genome, crossing two purebreds and expanding their gene pools can be “a phenomenally good idea,” according to one canine geneticist — if it is done conscientiously." But crossbreeding for a particular style of designer dog may not work out as intended; instead of the desirable traits, the resulting litter may have a combination of the undesirable traits of the two purebred breeds. Wally Conron, the originator of the Labradoodle (bred as a hypoallergenic guide dog from a carefully selected sire and dam) in 1989, noted that although the first Poodle-Labrador Retriever breeding produced a success, "our next litter of ten labradoodles produced only three allergy-free pups."
Crossbreeding has not been well studied in dogs, although it has been for livestock. The heritability of the desired trait being bred for (such as a hypoallergenic coat) needs to be known; "Heritability is the proportion of the measurable difference observed between animals for a given trait that is due to genetics (and can be passed to the next generation)." Without that knowledge, it is far less likely for a crossbreeding to consistently achieve an intended appearance or behaviour than it is for a purebred breeding. In addition, the goals of dog crossbreeding may be harder to define than the goals of livestock crossbreeding; good temperament may be harder to define and measure than high calf weight.
Designer dog breeders are often criticised for being more interested in profitable puppy production than in dog health and welfare. Wally Conron comments on the popularity of crosses after his introduction of the Labradoodle: "Were breeders bothering to check their sires and bitches for heredity faults, or were they simply caught up in delivering to hungry customers the next status symbol?" Designer dog puppies sometimes bring higher prices than the purebreds from which they are bred,. Finding a breeder who does health testing and considers hereditary compatibility of breeding stock is as important for a designer dog as it is for a purebred.
The fanciers of designer dogs respond with a reminder that all modern dog breeds were created from earlier breeds and types of dogs through the same kind of selective breeding that is used to create designer dogs. The Toy Poodle was bred down in size from larger poodles, most likely by crossing with various very small Bichon types, such as the Maltese and Havanese, although it occurred before the careful recordkeeping that is now done for modern purebred breeds. Most of the modern breeds have ancestries that include various older dog types and breeds; see individual breed articles for details of the origin of each breed.
Health of dog hybrids depends on their being descended from healthy parents; breeders who select their breeding stock for cost-effectiveness and who skip health testing for the same reason will not produce puppies that are as reliably healthy as those bred by more conscientious breeders. However, studies of longevity in dogs have found some advantage for crossbreeds. "There was a significant correlation between body weight and longevity. Crossbreeds lived longer than average but several pure breeds lived longer than cross breeds, notably Jack Russell, miniature poodles and whippets" Small designer dogs might also be expected to have very long lives, as they have both the advantages of small size and of crossbreeding, but that was not covered in the study. In general though, it is believed that crossbred dogs "have a far lower chance of exhibiting the disorders that are common with the parental breeds. Their genetic health will be substantially higher."
Many breeders of designer dogs take advantage of the fact that people like a pet that is unique; "It’s human nature to aspire to own something a little different, a little fancy or in short supply."
Hybridization to take advantage of the increased chance that a recessive detrimental allele will only be inherited from one parent, and therefore not expressed in the phenotype of the offspring, is only one strategy breeders can use to decrease the incidences of genetic defects. For example, large dogs such as the German Shepherd Dog often suffer from hip dysplasia, a multi-gene trait strongly affected by environment. Mating a German Shepherd, a breed known to have about a 20% incidence of this disease (ref:OFA), with a dog of a different breed not known to suffer from hip dysplasia like the Greyhound, reduces the likelihood that the cross-breed produced will suffer from hip dysplasia. Mate the same German Shepherd to an Otterhound (dysplasia incidence about 52%) or to a small dog such as a Pug (62%) or a Norfolk Terrier (37%), and the outcome might be considerably different. Breeding dogs (either of the same breed or different breeds) that have been tested free of dysplasia offers a similar result, with the added benefit of producing offspring that are less likely to carry the defect, unexpressed.
Knowing the disease incidence in the breed, and the genetic history of the individual, is ultimately important in dog breeding. Having the parental dogs genetically tested for defects known to be troublesome to their breed (or breeds, in the case of mixed parentage) will do as much, or more, than simply choosing dissimilar individuals with functional reproductive tracts. Genetic health must be approached from many angles. Some schemes are effective for the short-term, but disastrous in the long. Others are slow to take effect, but that effect is long-lasting.
Dog hybrids are not recognized by any major breed registry, as hybrids are not one breed of dog. If both parents are registered purebreds but of different breeds, it is still not possible to register a puppy as two different breeds.
If dog hybrids are bred together for some period of time, and their breeding is well documented, they may eventually be considered a new breed of dog by major kennel clubs (an example of a recent hybrid becoming a breed recognised by all major kennel clubs is the Cesky Terrier) New breeds of dogs must have a breed club that will document the ancestry of any individual member of that breed from the original founding dogs of the breed; when the kennel club that the breed club wishes to join is satisfied that the dogs are purebred, they will accept and register the dogs of that breed. Each kennel club has individual rules about how to document a new breed. Some minor registries and internet registry businesses will register dogs as any breed the owner chooses with minimal or no documentation; some even allow the breeder or owner to make up a "breed name" for their pet.
Dog hybrids, created by breeding two purebred dogs of different breeds, have the advantage of heterosis, or hybrid vigor, and may be stronger and healthier than either of the parents. This advantage can be progressively diluted when two hybrids are bred in the attempt to create a breed. The best way to continue taking advantage of hybrid vigor is from the breeding of two different purebred breeds.
Affinity clubs and web boards provide social opportunities for owners of the variously-labeled crossbreed dogs and a place for breeders to advertise puppies. There are also many other specific Designer Dog dog fancy associations such as the International Designer Canine Registry: http://www.designercanineregistry.com.
With the long-time popularity of the label cockapoo, used since at least 1960 and constructed by combining elements of its two contributing breeds (Cocker Spaniel/Poodle), it has become extremely common to find dog hybrids given labels likewise invented by portmanteau. The tendency for using such labels in a jocular way dates back at least to Queen Elizabeth's dorgis (Dachshund/Corgi). None of these have become recognised by any major registry as purebred breeds, as creating a new breed takes long periods of time, extensive record keeping, and determined breeders. However, as of 2006, the portmanteau words cockapoo and Labradoodle are found in some dictionaries. Label names such as these are most often found in for-sale ads, or on the websites that allow breeders to make up their own portmanteau word names for litters of hybrid puppies. The terms are only loosely descriptive and are seldom consistent; a cross between a Maltese and a Poodle, for example, may be advertised as either a "Maltipoo" or a "Moodle", and the cockapoo is also called a spoodle.