Yes, a dog can mate with a wolf and produce fertile offspring. All dogs are biologically the same species. The dog – man’s best friend – is a wolf in dog’s clothing. All dogs from the most beautiful, purebred, pedigree to the scruffiest of street dogs are domesticated wolves. Therefore there is no barrier to a domestic dog mating with a wild wolf.
It can be hard to believe this sometimes because through selective breeding the purebred dog varies tremendously in appearance and size. The difference in size of dog breeds greatly exceeds that of cat breeds. Also, the number of dog breeds exceeds that of cat breeds and there are far more purebred dogs in homes than there are purebred cats. In other words the percentage of purebred dogs compared to the total number of domesticated dogs is far greater that is the case for domestic cats.
This is because the dog has been domesticated for up to 30,000 years which is more than twice the time that the cat has been domesticated approximately 10,000-14,000 (as a maximum) years ago. And the reason why the dog was domesticated first is because they were needed as working and utilitarian animals. In those early days there was less concern over pets as companion animals whose role was to entertain people.
Selective breeding has also tended to breed out of circulation over-nervous and over-aggressive individuals. Dogs have become more playful and more placid. They have become better companion animals.
Early selective breeding was for a purpose as opposed to purely to companionship. They were utilitarian animals so a dog that was required to run fast was bred with long legs. If the dog was bred to go to earth to get burrowing animals their legs were bred to be short and their bodies round and long. And if they were bred, as is more often the case nowadays, to be lap and toy dogs (to be carried around as accessories) they are bred to be very small, petite and cute.
Breeding small dogs is relatively easy. All you do is you pick the runt from each litter and breed them over and over again. This results in dogs of much reduced size over a period of time.
There are several hundred dog breeds and each one has a breed standard as laid down by the dog associations. In Britain, there are six main groups of breeds that are officially recognised (as at 1996). Things obviously change. These groups are or were, gun-dogs, the hounds, the working dogs, the terriers, the toy dogs and the utility dogs.
Return to wild
Some domestic dogs have returned to the wild centuries ago. The dingo of Australia and the New Guinea Singing Dog are two examples. Feral dogs are essentially wild especially if born feral and they survive by scavenging on foods that humans do not want.