An interesting fact: All dogs regardless of size, shape color, etc when stripped down to their skeleton are identical to wolves. There are a few differences between the two but both can mate with each other and their offspring can reproduce with no problems. Some of the differences include mating times, tail curling, litter numbers... but for the most part the two different species are so identical that the scientific community debate is whether or not to classify both species as one. The current argument is that dogs are really domesticated wolves.
If I want to make my 10 pound dog's day all I do is rub on him and call him a big bad wolf. He loves it!