You might not think of behavior as a health issue, but behavior problems are the number one reason why dogs end up homeless in America. Dogs who pee on the furniture, growl at the children next door, or come at grandma like an out-of-control steamroller are no fun to live with. Many of these behaviors are just naturally hardwired into dogs, though, and it's our job as their guardians to teach them how to behave in a way that is acceptable to us. It is not the dog's fault if no one ever taught him how to behave properly, or if he has insecurities that cause him to "act out." It's probably not your fault either. It's very likely that you just didn't have the information that you needed when you needed it. However, you are the one with the big primate brain and the opposable thumbs, so if your dog is going to improve, it's going to be up to you to make it happen.
Please don't be disheartened if your dog exhibits embarrassing or even dangerous behaviors. We've all been through it to one degree or another, and you can get help. This is one area where an ounce of prevention truly is worth a pound of cure. It is much easier to train a puppy than to re-train an adult dog. But don't give up if you have an older dog with some behavioral issues. There are many, many training and management techniques that will change your life and your dog's life for the better. The following links offer some of the best advice that we've seen on how to understand, modify, and manage your dog's behavior. Even more importantly, finding a competent trainer or certified behaviorist in your area can literally be a life saver for your dog.
If your dog suddenly develops uncharacteristic behavior problems, you should always check first with your veterinarian for a possible underlying illness. Chronic or acute pain, neurological disorders, diabetes, Cushing's disease, seizure disorders, hypothyroidism, and other health problems can cause unusual behavior, from house training mistakes to aggression.