Why is my male cat very aggressive with a new female cat.

[sharon87]

First off, he is neutered. 

Recently I took in a female cat from the street(Rene) (Just fostering). She had mange so I confined her to a room. When I first took her in my male cat (Zack) was not neutered. Since Rene had mange I didn't let Zack near her but whenever she saw him, she would hiss at him. 

So anyways, she has basically been on lock-down for the past 3 weeks. What I did not realize is that they both could smell each other and they must have gotten used to the others smell because yesterday I decided to let them play together under supervision. She was okay with him. No hissing or anything BUT he just wouldn't leave her alone. He would jump on her and bite her. She at first just kept quiet but within a few minutes she started to hiss and swat at him. 

The thing is during this whole thing never once did he hiss at her or use his nails on her. So I'm just wondering whats up with my cat? He doesn't back down when she hisses and swats at him. He harasses her non stop. So I was just wondering why is my cat behaving this way towards the new cat. His behavior is very confusing... He doesn't seem to want to hurt her but he harasses her very badly..

Additional info:

Zack: Got him when he was 6 weeks. His foster mom informed me he was the smallest of his litter and would constantly get bullied. He is my first and only cat. I tried fostering before but didn't work out as the kitten that I was going to foster was bullying him and she wasn't even half his size! So I had to give them away to my sister to take care.

Rene: I took her in because she was in such a horrible condition. She had mange and was basically starving. I think she was dumped as she didn't move from the spot i found her for a month! She is a purring machine. As soon as human parts come into contact with her she purrs.. Very docile, Very loving ( I will never understand why her previous owners dumped her). She is not spayed yet. (Getting it done this weekend). I will foster her till she finds a suitable loving home.

 

[p3 and the king]

How long ago was he neutered? I am assuming it was recently since he wasn't when she came to you. It takes hormones awhile to get out of the system.  Sometimes a couple of months.  This could be the problem.  So reconfine her and then start a reintroduction process about 6 weeks after his neutering, the testosterone should be mostly if not all out of his system by then.

Also seeing as he has a history of aggression with fosters or newcomers, he may be a cat with an "only cat" personality.  This is common.  And you just have to accept it.  I am not saying you can't help and foster kitties in need, but do not expect him to be friendly with them.  You may need to keep him separated from them the entire stay.

 

[sharon87]

He was neutered like 2 weeks ago... 

To be honest the other time, was the one getting bullied so I was surprised this time he was the aggressor.

I will have to keep her separated anyways since she will be spayed tomorrow. Hopefully she will find a home in a couple of weeks time..

Thanks for the reply and explanation. 

 

[p3 and the king]

He probably has residual hormones that haven't left his system yet and her not spayed, she may be in heat?  Its common for them to go into heat at times of stress or getting over an illness.  Just keep them separated as much as possible for the next month or so and if she's still with you, start the process of reintroduction and see if it helps.  I'm guessing once the hormones have left the building, it will change a lot of the dynamic though.  With him, too.

 

[lamiatron]

agree with  @P3 and The King

Your male cat was just neutered, he could still have hormones coursing through his body. Also another thing to consider, even though your boy is neutered, and rene has not been fixed yet, she is still giving off some scent...and that could affect the way he behaves towards her, however, from your description, it doesn't seem like he's trying to hurt her, he's just trying to assert his dominance over her. this is very common in multi cat households. my Charlie does this to my Jet all the time. He will harass her and bother her, and even tho she is hissing, he doesn't stop. At the same time, they are very loving towards each other, and they groom each other, and sleep together, so i've chalked it up to it being aggressive play between the two. there are time where Jet is the aggressor too, but its a bit more intense with Charlie initiates the situation, as he's trying to assert his dominance.It could be that when your boy  was younger, he was more prone to being bullied, but now that he's older, he just want to be the boss of everything.

If you don't end up keeping rene, it would be best to just keep her separated from Zack until she gets adopted, especially since she will be spayed soon, you don't both your kitties to play and get into a fight and then your boy could really end up hurting rene during her healing process. if you end up keeping rene, then slowly go through the re introduction process, and hopefully it works out for you.

something to keep in mind, once rene gets spayed, she will come home smelling "different" to your boy from having been at the vet, and that could cause him to be more aggressive towards her. i haven't experienced this yet when i take my cats to the vet, i always take them together, but if i take one and leave the other one home, i keep them separated for a few days. what helps me, is giving both of my cats a bath (separately!!) before they see each other again. They both smell the same so that helps. 

also if you do end up keeping rene, you have to make Zack feel like he's still the Top Cat. giving him food first, giving him pets and acknowledgement first, giving him treats first. trust me it helps and works. you kinda have to stroke Zack's ego, and make him feel like he's still number one to you. another great way to deal with kitty aggression, in my opinion/experience, is to distract Zack with lots of interactive play. let him take the aggression out on the toy and not on Rene. Time outs also help. I will usually crate Charlie for a few moments, and then let him out and give him a treat for behaving better.

good luck to yoU!