I am not positive, but I think a male dog can smell a female dog in heat for about a 3 mile radius. I am shaking my head even as I type this, because that is a huge distance. I will see if I can find a "fact' on line and post if it is different than the 3 mile radius. They will breed through a baby gate if given the chance. The female can stand backward to it (instinct will tell her to do so) and the male will breed with her. They don't do it out of love for one another or companionship or loneliness (LOL
), just out of pure instinct.