Here is Demetrius in a standoff with my parents' cat, 'Possum. Demetrius is on 'Possum's turf - since he has diabetes and needs insulin shots twice a day, we bring him with us when we visit my folks in the Berkshires.
'Possum won't let Demetrius out of this room. She guards the door with her tail bristled out like a bottlebrush. She'll growl, wail, and hiss at him if he tries to leave.
Demetrius takes it all in stride.