My terrier is aggressive towards other animals

Question
About a year ago I rescued a terrier mix from the local dog pound. He is the most lovable dog I have ever had, but I am beginning to have problems with his aggression. We also have a cocker spaniel in the house who is getting up there in years and his health is failing. These dogs have lived together for a year without incident, but a month ago, the terrier began attacking the cocker. It has gotten to the point where the two can't be in the same room. The attacks are vicious, and it is almost impossible to pull the terrier off of the cocker. The worst part is that the cocker is blind and deaf, so the attacks are completely unexpected to him, he doesn't even fight back, he just lays down and cries. It's heartbreaking! Please help!!!  

Answer
I'm very very sorry, but I'm not going to be much help on this one.....

My impression is that you have a "changing of the guard" or a changing in the pack order.  Additionally, some dogs are ultra sensitive to the ilnness/weakness of another.  In some dogs, that brings out the best - they help guide the other dog and are extra gentle.... and brings out the worst in others - they target the weaker dog.

Example - My male gordon setter was all of a sudden getting into fights with another of my dogs... Sam was not starting them and it seemed like he was being picked on all of a sudden. He was only 8 and in apparent good health.  Only a month later I discovered a very fast moving bladder cancer that I had to put him to sleep as soon as I found it (since he was suffering and there was 0 chance of any improvement).

How did the other dogs know ??  beats me

It's not much help to understand the reason, if I can't offer any answers to modifying the behavior.  I suspect only someone who can actually see the dogs and watch the details of their body language could help - which means you're looking at a very good trainer or a behaviorist.

Again, I'm sorry I can't be of any more help.....

Beth Adams
Col Potter Cairn Rescue Network
www.cairnrescue.com