aggresive Aussie

[Sheltie/Aussie Mom]

I have a 9 yr. old Sheltie and a 2 yr. old Aussie. They have managed to coexist for 2 years. The Aussie is very aggresive and has been since we got her. It is getting worse though. The Sheltie recently had surgery and was gone for a week. When we brought her home, the Aussie doesn't seem to recognize that it is the same dog! The Sheltie has been shaved quite a bit and has lots of stitches around her neck. The Aussie is continually growling at her and attacking her. We are having to keep them separated. Help! What can we do about this aggresive dog?

[erdog3]

A lot of behaviour problems are borne from, boredom, lack of exercise and jealousy.
As you are probably giving a lot of attention to the one operated on, the other will naturally be more jealous.
All I can suggest, give the other some more attention, toys, bones and exercise.
Sometimes if they are both female, you can never get them to cohabitate in harmony, and you will just have to separate them.

[JakodaCD OA]

First and foremost I'd keep these two separated. While they may have gotten along up until recently, you now have a young aussie that is maturing and well, turning into a '***** '.
Also some dogs will pick on the weaker of the pack (your sheltie is a senior, just had surgery,) they can 'sense' when there is weakness.
How is your Aussie with dogs other than your sheltie? Is she just aggressive with her or is she aggressive and unmannerly with other dogs as well?
What do you do when these events occur? The best thing to do is PREVENT it before it happens.
It's really not fair to your older dog.
Definately keep them separated.