Aggressive Chow-Lab cross

by Alex
(Vancouver, BC, Canada)

We rescued our dog, Maggie, from the SPCA a few years ago. She was about 3 years old when we adopted her and we don't know her past except that she was probably abused a bit.

At first she seemed like a calm dog, although a bit timid, but within the past year she has been getting increasingly aggressive on leash and most recently, off-leash. She has taken to lunging and bearing her teeth at other dogs while on leash, but not all dogs, just chosen ones. When she is off leash at the dog park, she is usually fine and she has good interactions with other friends' dogs and dogs in her hiking group.

This evening, she was off leash and bolted toward a rottweiler who was on leash. A fight ensued and it was a few minutes before the dogs were separated. I have never seen her like this. She just went right after the dog and attacked it. I am afraid that the previous acts that were not dealt with are now leading to bigger, more serious problems.

I have enrolled her in many training classes and she always does well while in a training environment, but it is out in the real world that she doesn't do so well. Any suggestions?