My family has a 4 year old German Shepard female. We have had her since she was 6 wks old. We moved when she was about 8 months and since then she is very aggressive and does not back down easily. Just today she tried to eat a gentleman at our home who was invited to do some work for us. When I tell her everything is ok she doesn't get it. She has had her face ran over by a car in our driveway becasue she attacks the tires as people are leaving our home. She does not care for men. I am so frustrated and do not know what to do. She is very loving to our family and we just want her to back down. We live in the country so she is NOT chained, we have underground fencing over 4 acres of property. Please help, we do not want to have to get rid of her we love her but are not willing to continue to put up with this behavior. People do not liked to come to our house because of our dog.
It sounds like your dog has decided that it is the alpha dog in the family and therefore has taken over the role of protector in the pack. By chasing the tires when visitors leave, she will come to think that she has gotten rid of the 'intruders'. You may have good intentions in telling her 'its ok', but by doing this you are sending a message to her that you are worried about the visitors and so she should do something about it.
Firstly, you need to show her that you, and not her, are leader of the pack. This can be reinforced by several ways throughout your normal daily routine, such as insisting that you walk through doorways before her and controlling her movement around the house. She should always be fed last, after both you and the rest of the household has eaten. She should let you place your hand in her feed bowl whilst she is eating. When you come home don't greet her straight away, instead, say hello to the rest of the household and the other dog first. Tell her to 'sit-stay' and then greet her. If she comes to you for attention before you are ready, turn around and ignore her until she is sitting calmly. When out on the leash, she should not be pulling, instead allowing you to lead the way. When playing games with her, make sure you are the one to select the toy and initiate it, as well as being the one to decide when to end the game, taking the toy with you when you are finished. Keep up the obedience training with her, even if it is just for 5 to 10 minutes a day, as this will strengthen your place as leader as well as improving her obedience levels. All this will help her realize that she is no longer the alpha dog and therefore there she does not need to assume the role of protector of the pack any more.
When she starts chasing tires or behaving badly in front people, put a leash on her and lead her away to the 'time-out' zone without paying any attention to her at all, not even making eye contact. Leave her here until she calms down. You must ignore her completely during this as she will try and get your attention in any way possible. It will take some time for her to realize that she is no longer top of the hierarchy, but be patient and your efforts will be rewarded!
I hope this helps and all the best with your training!