Help! Emmett's an extreme guard kitty!
I have two indoor cats. Emmett, the younger, was found in a woodpile when he was just a few weeks old and fostered by my former pet sitter for about 5 months. She asked me if Stump would like a buddy so I agreed and adopted Emmett, who is now 3 years old. He's actually calmed down in the past 2 years but is still quite skittish; he often jumps if I move too quickly or even sneeze! Lately, he's been displaying an alarming new behavior: whenever another cat from the neighborhood comes into our back yard (we live in a townhouse with a wood fence), Emmett goes nuts. He jumps up and down, snorts, and gets a big fat tail. He has already shredded most of the vertical blinds and has started pulling up the carpet in front of the patio door. If the visiting cat comes up to the door, it's even worse. They both start flailing at each other against the door. My screen door is just one big hole at the bottom, thanks to these "guest cats." This morning it happened again. I shooed the other cat away, but then Emmett turned around, flew across the room, and tackled Stump, the older cat, and really upset him. I'm really worried about this behavior and its potential effect on Stump, who is 13.
Does anyone have any suggestions or advice? This behavior just started this summer and I'm not sure why. Maybe he's being territorial about our house. Whatever the reason, it's really worrying me and I'd appreciate any wisdom that any PetTalkers can provide! Many thanks!