Earlier today I was on my back porch when my big cat, General Eisenhower, found the next door neighbors black cat in the garden and ran him home. The black cat went over the fence, and in the house through the pet door. Ike stalked back and forth in front of the gate for a bit (he's too big to jump the fence like the other cat), and then sat down on the concrete. After a few minutes he jumped up and went flying around to the front of the house. I went after him, since we keep the cats in the back yard and don't let them roam. When I got around front I looked around and found him on the neighbors front porch, standing on the bench and peering in the window. Looking for that black cat I guess. I shooed him back to his yard, where he found a shady spot and watched the neighbors gate for the rest of the time he was outside. That's what I call territorial.