Many members of the dog family can interbreed to produce fertile offspring.
Molecular analysis indicates 4 divisions of canids:
The wolf (including the dingo and domestic dog), coyote, and jackal, all have 78 chromosomes arranged in 39 pairs. This allows them to hybridise freely (barring size or behavioural constraints) and produce fertile offspring. The wolf, coyote, and golden jackal diverged around 3 to 4 million years ago. Other members of the dog family diverged 7 to 10 million years ago and are less closely related and cannot hybridise with the wolf-like canids: the yellow Jackal has 74 chromosomes, the red fox has 38 chromosomes, the raccoon dog has 42 chromosomes, and the Fennec fox has 64 chromosomes. Although the African Wild Dog has 78 chromosomes, it is considered distinct enough to be placed in its own genus.
Dog hybrids kept as pets are prohibited in certain jurisdictions, or are classed as wild animals and must be housed in the same way as purebred wolves. For example, hybrids of the domestic dog with the wolf, coyote, dingo, jackal, fox, dhole, African Wild Dog, or Raccoon dog are prohibited in the State of Hawaii.
The domestic dog (Canis lupus familiaris) is a domesticated form of the Grey Wolf (Canis lupus lupus), and therefore belongs to the same species as other wolves such as the Dingo (Canis lupus dingo). Therefore crosses between these sub-species is unremarkable, and not a hybridization in the same sense as an interbreeding between different species of Canidae.
People wanting to improve domestic dogs or create an exotic pet may breed domestic dogs to wolves. Grey wolves have been crossed with dogs that have a wolf-like appearance, such as German Shepherd Dogs, Siberian Huskies, and Alaskan Malamutes. The breeding of wolf-dog crosses is controversial, with opponents purporting that it produces an animal unfit as a domestic pet. There are a number of established wolfdog breeds in development. The first generation crosses (one wolf parent, one dog parent) are generally back crossed to domestic dogs to maintain a domestic temperament and consistent conformation. First generation wolf-dog crosses are popular in the USA, but retain many wolf-like traits.
Some dingo-dog crosses have been deliberately bred as pets, but are turned loose due to behavioural problems. These crossbreds are accepted back into the wild dingo population where they breed with pure dingoes. In some parts of Australia, up to 80% of dingoes are part domestic dog. Dingoes are distinguishable from domestic dogs through DNA and through having longer teeth and longer muzzles.
The Australian Kelpie sheepdog is widely believed to be the result of crossing dingos with English herding dogs, but this (the dingo blood) is not upheld by breed documentation. The Australian Cattle Dog breed is known to have been influenced by the dingo.
According to the partwork "Animal Life and the World of Nature" (Vol 1, 1902-1903), Lord Walter Rothschild owned a dingo-wolf cross, bred by Mr and Mrs HC Brooke from a tame male dingo and a semi-tame female wolf.
An unconfirmed female terrier/fox hybrid was reported, and later euthanized (killed), in the UK. British gamekeeper folklore claims that terrier bitches can produce offspring with male foxes. Other dog breeds claimed to have hybridized with foxes are the Alaskan Malamute, Sheltie, Siberian husky, and most of the hound groups. The supposed hybrids (known as a dox) are likely to be natural variation in the domestic dog.
There has been a reported cross between a domestic dog and a South American fox, but the fox was a fox-like wolf, known as the maned wolf, and not a true fox.
In Saskatchewan, Canada there was another supposed dox, this time a female miniature Sheltie with a wild fox. There was a litter of three, but only one survived. The surviving (a female) was barren, and looked like an almost pure fox, with slight variations. However, the variability of dogs in appearance makes it impossible to determine whether an animal is hybrid based on looks. In most reported cases the dox had gold or yellow eyes, wired hair, and with black red and gray hairs covering most of the body.
Coyotes are solitary by nature; this trait is carried across to coyote-dog hybrids. This can result in problematical and unsociable behaviour which makes them generally unsuitable as pets. As a result, they may be abandoned or allowed to stray and be absorbed into the feral dog or coyote population. However if the coyote (or dogote) is found at a very young age and raised properly they can, in fact, become a pet much like some wolf-dogs are kept. Much time and effort must be put into them for this to occur.
Coy-wolves (Coyote/Wolf) have occurred in captivity or, rarely, in the wild where the choice of same-species mates has been limited. Coyote/Red Wolf hybrids have been found. Some consider that the American Red Wolf is not a true species because of DNA analysis that supports the hypothesis that the Red Wolf is a Gray Wolf/Coyote hybrid. This is sometimes used as an argument against the conservation of the Red Wolf.
The reason golden jackals differ in chromosome number is most likely because golden jackals have 2 pairs of chromosomes that are twice as long but contain similar gene content as 4 pairs of dog chromosomes. This might reduce fertility but it would not likely completely sterilize golden jackal-dog hybrids.
In The Variation Of Animals And Plants Under Domestication Charles Darwin wrote:
In Russia, Golden Jackal/Siberian husky hybrids were bred as sniffer dogs because Jackals have a superior sense of smell and Lapponian Herders are good cold climate dogs. Also Fox Terrier, Lunehund, and Spitz blood were bred for over generations and for almost 25 years have been dedicated to the forming and presice genes of the Sulimov dogs. As well as a superior sense of smell, important at low temperatures where substances are less volatile and therefore less pungent, Sulimov Dogs are small sized and can work in confined spaces. When tired, their normally curled tails droop, making it clear to the handler that the dog needs to be rested.
The jackal hybrids were bred by senior researcher Klim Sulimov, Senior Research Assistant at the D.S. Likhachev Scientific Research Institute for Cultural Heritage and Environmental Protection in Russia.
Male Jackal pups had to be fostered on a Husky bitch in order to imprint the Jackals on dogs. Female Jackals accepted male Huskies more easily. The half-bred Jackal-Dogs were hard to train and were bred back to Huskies to produce quarter-bred hybrids (quadroons). These hybrids were small, agile, trainable and had excellent noses. They are called Sulimov Dogs after their creator and may one day be registered as a working breed of dog. Twenty-five jackal-dog hybrids are used by Aeroflot at Sheremetyevo Airport in Moscow, for functions which include bomb-sniffing. Their breeding program dates back to 1975, but was not applied to bomb detection until 2002.
| Dog | Dingo | Coyote | Jackal | Fox | |
|---|---|---|---|---|---|
| Wolf | Wolfdog | possible | Red Wolf | Jackal hybrids | not possible |
| Dingo | Dingo hybrids | Coy-dingo | possible | not possible | |
| Coyote | Coy-dog / dogote | Coy-dingo | possible | not possible | |
| Jackal | Jackal hybrids | possible | possible | Unknown | |
| Fox | Dox (Unconfirmed) | not possible | not possible | Unknown |