Our rat terrier was adopted from a shelter a year ago. When we first got “Buddy” he was two years old, overweight and easy going. At first he was VERY passive and relaxed, the only thing he wanted to do was eat and sleep. When we took him to the dog park for the first time, he froze with fear and didn’t know what to do. That’s when we realized that he had never been socialized or taken to a dog park before. My wife and I work full time so “Buddy” had to stay home all day by himself watching Days of our lives and Oprah. The fact that we were gone didn’t seem to bother him or create any stress for him. During the first 7 months we took him hiking with us, we took him for long walks around the neighborhood and to the doggie park.  Little by little he started playing and running in the park with other dogs, in other words he was finally coming out of his shell. But then the winter came and he became an indoor dog, and that’s when the behavioral problems started. First he started peeing on the carpet, which up to that point he had never done before. Then he started getting more defensive when it was time to take a bath. You see, he has always been TERRIFIED of water…  When we first got him he used to stay still, with his tail between his legs when we grabbed him to taking to the bathroom. After 9 months living with us he started laying on his back and moving his torso when we put our hands underneath his body, making it very difficult for us to grab him without hurting his back. After 10 month living with us he started growling and showing us his teeth. He didn’t dare to take a bite at us but you could see that he was thinking about it. After 11 months living with us he has growled, become more aggressive and has finally bitten me. He bit me so hard that not only he ruptured my skin but he cut deep into my flesh. I was bleeding and had to go to the hospital where they gave me three stitches. He has also bitten my wife. We started taking him to the dog park again with the hope that this would change his behavior. But that is not the case, he has become extremely defensive of his territory and of us when other dogs approach. He has attacked and chase all types of dogs (German Shepherds, Rottweilers, Boxers etc) for no aparent  reason. One time he chased a Golden Retriever and clinched onto his back and didn’t let go. Picture a Golden retriever running at full speed for 25 yards with Buddy biting him on the back with his four legs on the air. He looked like a giant tick attached to that poor dog. When we finally managed to let him let go, he had a huge ball of fur in his mouth. I thought that taking him to the dog park would release his newly found aggression but that has not been the case, if anything he has become more aggressive. Now, I cannot even take him to the dog park because I’m afraid he might hurt another dog. I established my role as the alpha male in my relationship with Buddy, so I don’t know what is going on. He is a submissive dog all day until I decide to give him a bath. I don’t know what to do or what is causing this, PLEASE HELP. We’d really like to find a solution to my dog’s behavioral problems before he gets out of control. How can I make my dog not be terrified of the water?

There are two common reasons why a dog is aggressive towards members of his own human family:

1) He’s trying to defend something he thinks of as his from a perceived threat (you). For example, if you walk by, or make eye contact while your dog is eating, he growls. This is known as resource guarding, and though it may sound innocuous, there’s actually a lot more going on here than your dog simply trying to keep his kibble to himself.

2) He’s not comfortable with the treatment/handling he’s getting from you or other members of the family. This sounds as though it's the case with the bathing incident(s).

All dogs have different handling thresholds. Some dogs like lots of cuddles, and are perfectly content to be hugged, kissed, and have arms slung over their shoulders (this is the ultimate “I’m the boss” gesture to a dog, which is why a lot of them won’t tolerate it.) Others – usually the ones not accustomed to a great deal of physical contact from a very young age – aren’t comfortable with too much full-body contact and will get nervy and agitated if someone persists in trying to hug them.

Another common cause of handling-induced aggression is a bad grooming experience: nail-clipping and bathing are the two common culprits. When you clip a dog’s nails, it’s very easy to “quick” him – that is, cut the blood vessel that runs inside the nail. This is extremely painful to a dog, and is a sure-fire way to cause a long-lasting aversion to those clippers.

Being washed is something that a great many dogs have difficulty dealing with – a lot of owners, when confronted with a wild-eyed, half-washed, upset dog, feel that in order to complete the wash they have to forcibly restrain him. This only adds to the dog’s sense of panic, and reinforces his impression of a wash as something to be avoided at all costs – if necessary, to defend himself from it with a display of teeth and growls... and sometimes even bites.

The instant he starts to show signs of stress, stop immediately and let him relax. Try to make the whole thing into a game: give him lots of praise, pats, and treats. Take things slowly. Don’t push it too far: if you get nervous, stop. Trust me... your nervousness feeds directly to your dog! Emphasis should be placed on keeping YOU calm and keeping your dog calm.

Dogs show aggression for a reason: they’re warning you to back off. Very few dogs bite without some sort of warning first. Look for the warnings (growling.. showing of teeth... hair up on back, etc.) If your dog just can’t seem to accept being bathed... no matter how much practice you put in, it’s best to hand the job over to a professional.

You are handicapped in a sense because you do not know what the dog's background is. He very well could have had some bad experiences that are triggering this behavior. But one thing is for sure -- The best treatment for dominant, aggressive behavior is consistent, frequent obedience work, which will underline your authority over your dog. Just two fifteen-minute sessions a day will make it perfectly clear to your dog that you’re the boss, and that it pays to do what you say. You can make this fact clear to him by rewarding him (with treats and lavish praise) for obeying a command, and isolating him (putting him in “time-out”, either outside the house or in a room by himself) for misbehavior.

Also... brush up on your understanding of canine psychology and communication, so that you understand what he’s trying to say – this will help you to nip any dominant behaviors in the bud, and to communicate your own authority more effectively. I cannot stress this enough.

Don't hesitate to seek the help of a professional if you need to. 

And... I would not be taking him to any dog parks unless he is on a leash! 

I agree on the bathing.  Twice a week is way too much.  Has he been neutered?  I don't know if you mentioned this or not.  That could be a problem also.  A trainer is a good idea also.  Good luck