I just read a real good ariticle about coyotes. In a very large study of some very large coyotes, like 50-75lbs they did DNA testing. Not one of them ahd any traces of domestic dog in them. They explained this fact very well. Even though they are capable of breeding each other and often do, the survival rate of the pups is very slim. The domestic dog will not stay around to help raise it as the male coyote will, so they usually die off from starvation and predation from other coyotes.