My GSD mix has lived with our cats since we brought her home at 8 weeks. They have put her in her place for months. About a month ago, she started nipping at them if they'd approach her treats/bowl/toys. It gradually got worse and she began full on strikes towards them for no reason. She could be asleep and then wake up, walk around the couch, and decide to pounce on a cat. We removed the toys. We have handfed, but that doesn't seem to make a difference, as she has never been aggressive towards us humans. She went after my older GSD once, and the older dog definitely let her know who was boss. I just don't understand why after 11 months, she'd decide she wanted to hurt the cats. Any ideas? Sometimes the toys she takes are CAT toys and she gets pissy about those too...