I think Misty recognizes cats by their look, and not by their smell. She leaves all six of my cats alone, but chases stray cats. There are two orange cats next door, and I have an orange cat. When I open the door to go out, if one of the next door orange cats is in view, Misty charges out the door, barking and chasing, but if Charley, my orange cat is outside the door, Misty calmly walks out and ignores him. Misty would keep all stray cats away from my property, trouble is, I only let her outside when I'm going out.