Determine that Neutering was Complete
My cat is ten years old. This last year he has been climbing on the back of another male cat that we have (who is more subservient) and biting his neck. He holds him still and grinds and sometimes cries out. He has also been growling and hissing at our dog who he has known since a kitten. Now my dog seems to be afraid of him.
Nobody is having a good time at your house, including the tough guy. Some would consider his bullying a punishable crime; others might advocate allowing nature to take its course. They would all be wrong. Cats are motivated differently; we humans and our dogs don’t speak their language.
A new unseen influence has clearly entered the picture, most likely coming from outside your house. Neighbor cats or wild animals skulking about can cause an indoor cat to feel trapped and anxious. Unable to confront a perceived intruder your self-appointed one-cat security force may be redirecting his angst toward his housemates.
Booby trapping your yard with a Scare Crow or Cat Stop and covering the lower portions of your windows with window film will diminish all of your pets’ exposure to outside agitators. Environmental enrichments like floor-to-ceiling cat trees, hide boxes, and stalk and pounce games will allow your tyrant and his subordinates to act out their primal grinding in healthier ways.
Your other pets regard this feline marauder with disdain, muttering epithets that are not fit to print. But he can be rehabilitated. Testicles can be retained internally so be sure this boy was completely neutered by having his testosterone level checked. A Feliway pheromone diffuser would promote a social emotional state; the medication paroxetine can reduce anxiety and aggression. Take charge before this aberrant behavior advances to fighting and soiling.