Hybridization between wolves and dogs typically occurs when the wolf population is under strong hunting pressure and its structure is disrupted due to a high number of
free-ranging dogs. Wolves typically display aggressiveness toward dogs, but a wolf can change its behaviour and become playful or submissive when it becomes socially isolated. Admixture in the wild usually occurs near human habitations where wolf density is low and dogs are common. However, there were several reported cases of wolfdogs in areas with normal wolf densities in the former Soviet Union. Wild wolfdogs were occasionally hunted by European aristocracy, and were termed
lycisca to distinguish them from common wolves. Noted historic cases (such as the
Beast of Gévaudan) of large wolves that were abnormally aggressive toward humans, may be attributable to wolf-dog mating. In Europe, unintentional mating of dogs and wild wolves have been confirmed in some populations through
genetic testing. As the survival of some Continental European wolf packs is severely threatened, scientists fear that the creation of wolfdog populations in the wild is a threat to the continued existence of European wolf populations. However, extensive admixture between wolf and dog is not supported by morphological evidence, and analyses of
mtDNA sequences have revealed that such mating is rare. In 1997, during the
Mexican Wolf Arizona Reintroduction, controversy arose when a captive pack at
Carlsbad designated for release was found by Roy McBride, who had captured many wolves for the recovery programme in the 1970s, to be largely composed of wolf-dogs. Though staff initially argued that the animals' odd appearance was due to captivity and diet, it was later decided to euthanise them. In 2018, a study compared the sequences of 61,000
single-nucleotide polymorphisms (
mutations) taken from across the genome of grey wolves. The study indicated that there exists individual wolves of dog-wolf ancestry in most of the wolf populations of Eurasia, but less so in North America. The admixture has been occurring across different time scales and was not a recent event. Low-level admixture did not reduce the wolf distinctiveness. In September-November 2018, in the
Osogovo mountainous region along the border between Bulgaria and North Macedonia a putative grey wolf was recorded by camera to be living with a pack of 10 feral dogs, and by its behaviour and phenotype was assumed to be a wolf-dog hybrid. == Breed-specific legislation ==