Longtime companion cats suddenly turn on each other

Dear Dr. Fox: We have two wonderful 14-yearold cat brothers who have always gotten along well. Out of the blue, one day in January, Spunky attacked Gus. It was definitely not play, and was unprovoked.

They have occasionally turned on each other if they have seen a strange cat walk through the property, but it is over quickly and they are friends again. This time has been different. For weeks, we could not comfortably leave them alone if we had to go out for a while.

There has been some improvement, but this has been going on for almost three months. They can be very loving — bathing each other, sleeping in the same room and sometimes even sleeping on the bed together. But often when Gus walks away and Spunky follows him, Gus will look back, spit, growl and run, which causes Spunky to pursue him. If I don’t get there in time, there is a very vicious attack.

They do have an enclosed yard with special fencing that prevents them from getting out. They are never out there without being observed, and when out there, they never fight. Gus has no problem if Spunky follows him outside, and vice versa.

It is as if Gus cannot forget the original attack, and when Spunky follows him, it brings back the memory and he cannot help himself. Then his growls and hisses get Spunky going. I use a spray water bottle to break them up, but it has been going on for so long I am afraid the behavior is just being reinforced.

I should also mention they are both in very good health. Gus has been on thyroid medication (methimazole) for the past year and is doing very well.

I would appreciate any suggestions you can give that could bring back our happy, peaceful household. — J.M., Fairfield, Connecticut

Dear J.M.: This problem is all too common, and you are correct in assuming that it was the stray cat outdoors (scent, sounds and sight) that made one of your cats redirect aggression toward the companion cat he lives with.

This traumatic event will not be forgotten by Gus for a long time, even though they may groom each other and sleep together. This is one of many reasons why cat owners should not allow their cats outdoors to roam free.

Gus will be especially on edge when walking past and away from Spunky. His thyroid condition is adding to his stress, along with any spray-bottle or other discipline/intervention you may instigate; such things will scare both cats and probably make matters worse.

I would try grooming each cat in turn, early in the evening, while they are both on the floor or sofa with you. Then try massage and any interactive games you can engage in to draw them both together, such as chasing a laser light or a lure on the end of a string. Find what treats they like and call them to you at random times so they both come and receive a treat at the same time.

Repeated close proximity provided by these pleasurable activities may be the best hope of Gus overcoming this traumatic event.