Question on Odd Male Cat Behavior

Question
Hoping you can help. I have a 7 year old neutered orange tabby male cat.  For the last year he's been exhibiting really odd behavior towards two of my other cats.  He will literally pounce on two of my female cats (one 15 spayed female, and the other is 10 and spayed).  He tends to favor one more than the other.  But when I hear the hissing and cat screams, I rush over and his tail is all poofed out and he runs away.  I have noticed that catnip magnifies this behavior to where he will scratch one cat.  So I stopped  giving him cat nip completely.  I've noticed it for about a year.  I tried giving him some calming treats which help some, but don't completely stop the behavior.  I've taken him to the vet and he's healthy. I've been told this is a behavior issue and to re-introduce him slowly. I've done that but it has not helped.  Recently the behavior is even more odd. One night last month I hear rumbling from the basement. I had assumed two cats were possibly fighting but I didn't hear any hissing or anything. But when I got down there he was the only one down there running around with his tail poofed out. He didn't look scared at all.  I did some research on what the tail poofing out means.  They usually do that in defense mode or aggression mode.  Not sure why he would pick only those two female cats to be aggressive to? And I can't for the life of me see how he could feel the need to be defensive. They do not go after him and usually anytime he's within sight of them they start growling. I thought maybe the tail poofing was in response to the other cats screams and hisses.  But then two days ago he comes from the basement. All the other cats are upstairs on various couches or chairs relaxing. His tail is poofed out, but not the hairs on his back.  Then he starts rubbing on one of the chairs and seems calm and content. Not either aggressive or defensive.  At first I thought that maybe his behavior was in response to my one other male cat being diagnosed with HT early in the year. I also thought maybe he could be trying to come the dominant male, but the behavior keeps getting stranger. Thought that it was stress of some kind because they are close buddies, but then why pounce on two specific female cats?  I've tried playing with him more, thinking that it had to do with not getting enough attention, but giving him more play time and attention has not had any affect on his behavior. I thought maybe it was an animal outside (because I live in a rural area) that might be spooking him,  but being winter, deer are pretty much the only animals around mostly.  And it seems his behavior is getting stranger.  I'm at a loss as to what is causing this strange behavior. Hoping you may have some insight as to what may be causing this.

Answer
Hi Mel,
I doubt if I can give you any kind of an answer that will help for a number of reasons. This most certainly does sound like a behavioral issue and I am not a behaviorist. I am also not a vet and cannot diagnose anything. I can make some suggestions but that is all.

While this behavior is not common, it is also not rare. Male cats, especially neutered ones, can have hormonal issues that can cause this type of behavior pattern. Sometimes it provokes a sexual aggression response in the cat, other times it's just becomes an actual and very dangerous aggression such as a territorial type aggression.

I don't know how many cats you have but a crowded house can cause this type of behavior as well. It is estimated that each cat needs at least 120 square feet of personal space to be stress-free. So small houses or apartments can make some cats go bonkers over time.

Changes in diet can affect a cat. Diets filled with dyes, and junk ingredients are not helpful.

Some cats need kitty anti-depressants at times. My mom used Amitriptyline on her cats with good results after a stray got in and sprayed a wall. I have used it for short terms problems and then tapered my animals off of it as well.This would be something you need to talk to your vet about.

You might want to try some Feliway as well, which is a pheromone that can be sprayed around the house. There is even a diffuser for it to keep it in the air. It has a calming effect on cats- so some owners report.

You say that the vet declared the cat healthy but what kind of tests were run? While it is not probably it is always possible that there is some sort of tumor issue going on at the site of the cats pituitary gland or even the adrenals that can cause some erratic behavior. Even a brain lesion can cause this.

You could consult with a pet behaviorist but make sure that if you do, that they are a DVM and not just some phd. I wouldn't trust one that wasn't a vet but that's me.

I hope that this might help some Mel. Good luck and feel free to re-post this to one of the vets in here as well.