My Male Cat Has Become Aggressive With Other Cats

CatChannel behavior expert Marilyn Krieger discusses ways to reintroduce cats to each other

By Marilyn Krieger | Posted: February 26, 2010, 3 a.m. EST

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Q: My 7-year-old male cat, Joey, has suddenly turned aggressive toward my other female cats. He is literally trying to kill the two girls. I have him in a separate room now and I am afraid he may have to be put down. The fear in my house is pathetic. I have never heard such screaming, or seen such fear in my entire life of having cats. My baby calico urinates from fear when Joey enters the room. He will look right at her and lunge. I have to throw a pillow or shoe at him to make him stop. Joey has always been sweet to all the cats and licked their heads when they approached. All of my cats are fixed. What happened?

A: The sudden behavior change Joey is exhibiting could be the result of either a medical problem or a situation that triggered a behavioral reaction. First, take him to your veterinarian to check for any possible medical or neurological causes that might be causing the behavior change.

After Joey is given a clean bill of health, approach this as a behavior problem. One possibility is that Joey is displaying redirected aggression. Redirected aggression occurs when something happens in the cat’s environment that causes an aggressive response. Typically, the response is directed toward the nearest cat or human. In Joey’s case, it is possible that there was an outside cat that triggered his anxiety. Your two girls could have been nearby, becoming the objects of his frustration. Loud noises, startling events and sudden changes may have also triggered this response. Unfortunately, sometimes long after the original triggering event has occurred, cats still have a negative associations with whoever they acted out on. And it is natural for the victims of the aggression to respond either fearfully or aggressively.

This unfortunate situation can be turned around by keeping Joey separated from the two girls while reintroducing him to them. Joey must be kept separated from the girls for the duration of the reintroductions. Start with scent-pheromone exchanges. Cats have scent glands on their cheeks that produce pheromones that cats perceive as friendly. Use three clean socks or small, soft towels and gently pet each cat's cheek with the object. Put the two towels, or socks that were used to pet the girls’ cheeks in Joey’s room. The towel that has Joey’s scent on it should be placed with the girls. The pheromone-laced towels/socks should not be placed near food or litterboxes. These scent exchanges should be done twice a day, each time with clean towels or socks. The goal is to change the cats' associations and experiences with each other.

All three of the cats need to respond favorably to the socks before adding another mutually enjoyable activity. Food can be used to help successfully change their feelings about each other. Feed the cats simultaneously, separated by the closed door. At first the food bowls may need to be back away from the closed door. Gradually, the food bowls can be inched toward the closed door at each meal until they are next to the closed door.

After your cats are enjoying their meals together, while separated by the closed door, add another activity. If your cats enjoy playing, you can encourage them to play under the door with each other by slipping a toy under the door that has something to play with on each end.

Only after all three of your cats are participating without stress, in the activities, open the door during meal times. It’s important to back their food bowls far away from the door. Joey’s bowl should be in his room, as far from the entrance to his room as possible, and the two girls' bowls need to also be placed away from the door as well. The food also needs to be very delectable to all three cats. Initially, keep the door open only while they eat, then close it. If there are no sign of aggression or stress, gradually increase the time the door is left open at each meal time. At any signs of problems, close the door and proceed slower.

It may take a few weeks until your cats start to change their relationships with each other. They might not be best friends again, but they should eventually be able to at least tolerate and be around each other without committing acts of violence.   




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Reader Comments

Sheryl    Houston, TX

1/15/2013 9:36:01 PM

Am I the only one that is disturbed by the fact that she is willing to kill her cat over this behavioral issue?! There are many ways to deal with animals and work with them to evolve their personalities more favorably. Please, please, please if you cannot work with them then at least place them in another home. To raise them as family and then kill them is simply inhumane.

daniel    seattle, WA

12/10/2010 3:01:39 PM

we have 2 brothers that are a year old now, jack an nash, they have always played well jack was a little rough but now that they are a little older nash sneak attacks jack in a very aggressive way, causing head wounds, we had planed on kittins in the future so niether of the brothers are fixed, but i think after reading your article somthing outside the house must have happened for nash to turn aggressive on his brother who was probably present when the trauma happen, thanks for the insite an nash is probably going to get snipped

Anne    Richmond Hill, ON

11/23/2010 12:43:28 PM

I have 4 cats, 3 girls and a boy. Karly and Willow are 1 year and 3 months old, Cubbie is 9 months and Sophie is 6 months, all rescues. All are spayed/neutered except Sophie due to a undiagnosed liver issue and will be spayed later on if her vet feels she is healthy enough. All except Sophie were adopted when they were 8 weeks old and are all very close. Sophie was rescued almost 2 months ago when she was tossed out into the street. The first few days were rough, Sophie was scared but Karly and Cubbie coaxed her out of the bathroom and helped her adjust. Cubbie especially. All have been getting along great until the past couple weeks where Sophie has been exploring new places and new sleeping quarters. Karly has suddenly become aggressive and chases her, there have been no physical fights that I know of but clearly Sophie is scared of Karly. If she gets too close Sophie usually leaves or will growl at her. This only happens once every few days and yet there are times when they can lay on the bed together and all is fine, Karly will even try to play with Sophie. I'm thinking Karly is feeling upset because Sophie has taken over a few of her favorite places and her favorite playmate Cubbie. Could the fact that Sophie is not spayed have something to do with it also? Or, could Karly be sensing that something is going on with Sophie's liver? I'm just worried that the stress Sophie is feeling from Karly chasing her might continue to cause her Alt enzyme level to be raised...other than this issue Sophie has tested perfectly normal for everything else. Am I just being overly protective?

Amanda    Long Valley, NJ

9/29/2010 1:43:45 PM

I have a cat that is 11 and he started showing this aggression last year. The aggression is so bad now that he attacked me and my husband and is living in a bathroom because he is so aggressive. My cat has become completely unpredictable and we are terrified of him. He got a clean bill of health and is now 1 week on anti-depressants, but I am not seeing much improvement. Any ideas out there?

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