Unaltered female dogs of breeding age go into heat about twice a year, giving off a scent that male dogs find impossible to resist. A male dog can smell a bitch in heat from up to 5 miles away. If unaltered female dogs live in your vicinity, you can help reduce the potential for an unplanned breeding between your male and the dog in heat by taking a few proactive steps on your own.
Neuter Your Dog
Neutering your male prevents him from impregnating a female as well as provides behavioral and health benefits. If you neuter your male, he’s less likely to be lured away by the scent of a female in heat, as neutered males generally lose their sex drive. Even if he is attracted, he won't be able to do anything productive about it. Neutering reduces roaming tendencies, which can keep your dog safe from harm like traffic accidents and fights with other dogs or wild animals. It also limits testicular cancer risk, urine-spraying and aggression.
Keep Him Contained
Keep your dog indoors or in a secure outdoor containment system. An unaltered male dog will go to great lengths to escape confines including gates, fences and tie-out restraints. If a female in heat is nearby, you may find your dog exhibiting excitable behavior, digging or trying to escape otherwise, or pulling at the leash when you walk him. Redouble your efforts to keep your dog in place. An unaltered male's better off inside when a female's in estrus in the neighborhood.
Teaching your dog to sit and stay on command won't necessarily stop him from running off in pursuit of a female in heat, but it will help you maintain a greater degree of control than if your dog doesn't see you as a pack leader. Your dog should respect you as the authority in your household and respond to your commands. Solid training won't eliminate the male's desire to mate, but it will be a hedge against his ingrained urge when he detects the scent of a receptive female.
Reduce Interaction Potential
While it's not always possible to know when your male dog will come in contact with a female in estrus in a public or community setting, be proactive in your efforts to keep him away from female dogs known to be of reproductive age. Keep your dog on a leash in public, and monitor activity in dog classes and in your neighborhood. Never leave your dog unsupervised.