What You Need to Know About Sexual Aggression In Neutered Cats

In the absence of testosterone, a cat’s masculine behavior is not inactive, simply less active.


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Sexual behavior by cats is a pretty gnarly business. A male waits for his moment and then darts after the female, pouncing on her from behind, biting her in the neck and pinning her to the ground, while he intromits his barbed penis. As he withdraws, the backward-pointing spines on his penis lacerate the female’s vagina, causing her to scream and roll away, and she may smack him if he doesn’t get out of range quickly enough.

All in all, a pretty unpleasant sounding experience though, surprisingly, the female will tolerate such ravishes multiple times from multiple suitors when she is at the peak of estrus. Most of us don’t want this type of behavior going on in our homes, and neither do most pet owners want an intact male cat around for other reasons; notably, intact males are generally more aggressive, frequently engage in objectionable marking and mounting behavior, and have a constant eye for the door, particularly when a neighboring queen is in heat. That’s why most cat owners who are not specialist cat breeders gladly accept neutering, in addition to birth control reasons.

Mega Masculine Kitty

As we all know, neutering is very successful in cats at eliminating male-typical behaviors, curtailing most of these behaviors with something like 90 percent efficacy. Many of these male-typical behaviors disappear soon after neutering, though some may persist for weeks, months or even years.

With mounting, at least, prior sexual experience has been shown to persist longer when the neutered male is constantly presented with a female in heat, as you might well expect. But there are other factors operating here, too. It is true that a neutered male is not an “it” but is rather a male lacking significant levels of testosterone.

Masculinization is a process that occurs in utero as fetal testes secrete testosterone and cause masculinization of specific brain regions, particularly the preoptic area of the anterior hypothalamus. This area of the brain is activated by testosterone to produce full red-blooded male behavior. In the absence of testosterone, it is not inactive, simply less active.

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I like the analogy of a dimmer switch, by which the light is turned down but not off. It has been shown in rodents but not yet in dogs and cats that a male fetus flanked on either side by other male fetuses can be “super-masculinized” by transamniotic transfer of small amounts testosterone from its two neighbors.

Such a cat (or dog) might have more residual maleness and be more prone to exhibit male-typical behaviors after castration, which brings me to my main point. The various male behaviors that I have described, including inter-male aggression and sexual aggression, may not be completely suppressed and may persist for years following castration of a super-male. It is possible that this explanation accounts for the 10 percent failure rate of neutering in male cats in suppressing all sexually dimorphic behaviors.

Problems With Neutered Males

Now back to the subject of sexual aggression, but this time in neutered males. I have seen several cases of aggression by neutered male cats to females that takes the form of sexual aggression.

Unlike territorial aggression or fear aggression, the pair of cats may get on perfectly well for most of the time but, just occasionally, the male, charges after a neutered female cat, who is clearly not receptive and screams as he launches himself at her from behind, biting her in the nape of the neck and wrestling her to the ground with fur flying—a cookie cutter replication of the sexual act, though not necessarily involving intromission.

I first came to this conclusion many years ago and formulated my own plan for dealing with it. I reasoned that odor is a particularly important sense to a cat and that any self-respecting male should be able to pick up the odor of the same or opposite sex. That is certainly true of an intact male cat who can detect the odor of a female in heat from several blocks away, but a neutered female should not hold the same olfactory attraction.

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Nevertheless, by not smelling like a male she could be viewed as a target for the unwanted sexual advances of a neutered super-male Romeo. The antidote for this situation, I surmised, was to play an olfactory trick on the male by making the female smell like a male. This can be achieved quite easily by applying a male pheromone, like androstenone, to the female’s rump every so often.

I happened to have a bottle of this substance from Sigma sitting in my office as a remnant of a pheromone study that I was conducting on litter boxes some years prior and resolved to try it in the next case of sexual aggression I encountered between a neutered male and female cat in a home.

The situation presented itself fairly quickly. The cats in question were an elderly female cat that had been blinded in a fire and a younger amorous, neutered male who engaged precisely in the behavior I just described. I made up a dilution of the androstenone and had the owner apply the pheromone to the female’s rump on a daily basis.

The aggression was stopped in its tracks. He would come screaming around the corner ready to have his way with her when all of a sudden he would stop in his tracks and look puzzled as if to say, “Excuse me, sir, I must have you confused with someone else.”

I successfully used laboratory-grade androstenone to treat presumed sexual aggression in several other cats subsequently before finding a readily available source of androstenone in the form of an aerosol made to help pig farmers detect estrus in gilts. This particular pheromone, which is found in boars’ saliva, is aerosolized and applied to the rump area of the pig. Then, when pressure is applied to the pig’s lower back, she will stand erect ready to be mounted if she is in heat.

The presence of the pheromone makes this pressure test more reliable for estrus detection. Pig farmers also discovered that if the aerosol was applied to the rumps of pigs being mixed in groups, that there was less fighting between them. I imagine this is because each pig on smelling a neighboring pig would consider him well endowed with maleness, a force to be reckoned with and, thus, would keep his distance.

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Several of my cat-owner clients have tried using Boar Mate to treat sexual aggression in their cats with the same degree of success that I had with chemical grade androsterone. One even reported that it was only necessary to spray the aerosol onto a pad and gently apply it to the female cat’s rump every other day to keep inter-cat sexual aggression at bay.

I have often wondered whether applying androsterone liberally to the rumps of cats feuding for any reason might be helpful in addressing these sometimes thorny problems of inter-cat housemate aggression, territorial or otherwise. After all, who would pick a fight with any cat wearing androstenone cologne and smelling like Arnold Schwarzecat? As far as the cat is concerned, it may be best to go about one’s business quietly under these circumstances. 

65 thoughts on “What You Need to Know About Sexual Aggression In Neutered Cats

  1. I have a 7 month old female house cat she has got out the house a few times and I believe she is about 3-4 weeks pregnant, my male cat who has been neutered (7 months ago) is trying to mate with her she is screaming out when he is trying this.
    Why is he doing that? Also what do I do?

    1. Sorry you question is really surprised me. Just out yourself in her shoes and have a think about it. They are almost like human but more like human kids that need adult humans to look out and take care of them. Why didn’t you spay your female cat when she was younger maybe about 3 months old? You can do it too young. A good and caring vet would be able to tell you that no matter male or female, you must get them fixed and then rested to recover in the proper way. I hope you will do that at the right time after she gives birth and nursed her kittens. I also hope you are going to spay and neuter the kittens when the reach the right age!

    2. same here(except she hasn’t escaped). from what i’ve read if the neutered male actually has sex with her it can help end the cycle and then you can get her fixed. since she’s escaped outside i’d get an ultrasound to make sure she’s not pregnant then get her fixed.

  2. Where can I get some of this hormone? My 2-year-old neutered male has started harassing my 10-year-old spayed female and it cannot be allowed to continue.

    1. I would also be interested in this hormone. My 4-year-old male, who was neutered very young as a kitten before I got him at 12 weeks has begun attacking my 7 year old female who raised him as his mother after he moved in with us. He has been biting her hard enough to leave marks on her that I can feel. I’ve decided to take her to my vet and to keep them separated when I’m not at home, but she doesn’t act like she is afraid of him. In the past when I put him in a room when he’s attacked her in my presence, she sits right be the door. This seems to have gotten worse in the last few days. They are both indoor cats. I also have an indoor-outdoor female who he leaves alone. In addition, I have been feeding a homeless male, who I cannot pet, who was neutered about two weeks ago at a homeless cat clinic (we caught him in a humane trap), outside on my back porch. Could that have anything to do with my inside males behavior? I find this very distressing.

        1. I have the same problem, and my female, is a dwarf, she has a normal body and very short legs, (yes, very cute cat), and my male cat, a rescue keeps attacking her and I separate them, she’s got anxiety when he’s around, she does want his attention, but not that way. She seeks refuge from my husband, or myself and we have to separate them when we are not home, or we fear that he will kill her. He’s a good boy over all, fun and funny too, but when it comes to her, it’s just not good, and it’s getting worse, I read that book Psyco Kitty by Pam Johnson-Bennett, but none of that helped so far.
          Did you find a solution? We think we may have to re-home him, but we don’t want to put him in a shelter, where he’ll get lost in an abyss of too many cats who also need homes.
          Did anyone give you any solutions? Seems like there are a lot of questions but no answers.

          1. DID ANY OF YOU READ THE ARTICLE?! The article has literally all the answers!
            The comment section are for those who have further questions or results from using the practices discussed in the article, not for those who didn’t read the article and would rather have their answers handed over on silver plate.

          2. People who ask questions in the comments without bothering to read the article should not have kids of any kind. Fur or human. FFS

  3. yes I want this for my 11y old boy who was spayed as a kitten. where can i get it
    he constantly jumps on his sister, sprays in the garden, humps the comfy blanket. on further research think he has too much testosterone

  4. My 5 year old male neutered cat who has never made an aggressive more or even put his claws out with any person or child (he will let my 2 year old niece pick him up and kiss all over his face like the most tolerant sweet boy i have ever seen..un catlike in every way) tried to kill our 16 week old female 2 days ago. She spent the night in the emergency cat hospital with stiches almost half way around her entire lil body mid belly level. Im devastated. He never took their meet and great well so we kept them mostly apart as he appeared to walk through the house hunting her down like a lion. She had been able to escape some close calls prior by goin under the sofa where he couldnt fit. Unfortunately my son (who sleeps with the older cat) got up to use the rest room in the middle of the night and forgot to shut his door. Hence we woke up to the screaming nightmare shortly after as he caught the kitten who was probably sleeping. I love them both dearly and the male is my “first born” so its definitely his house. We have a two year old Bullmastiff female pup who is submissive despite her 130 lb weight advantage to him as well. He launched and pounced and tackled her when she was a baby too but never injured her! Not that he has grown to love her but they stay out of eachothers way. He is def still the boss of her though. Any suggestions or help would be greatly appreciated. I can not rehome an animal. I dont have it in me.

    1. Wow, I just read yourr post and it seems so much like what we are going thru with our older male and much younger female kitten. I never seem to see replies on these posts though. Did you ever get any help with you problem. I am so worried about what our male (Sonny) may do to our young female (Rosie) it’s so distressing for the whole family and we cannot bare the thought of having to rehome one of them. Prior to this meeting, I would never have thought Sonny could become so aggressive. Regards Jo

      1. We recently tried ferimonecollars on 2 of our cats that were fighting & it seems to be working.the 1st month we only put one on the female because she seemed to be the aggressor & things calmed down but the 2nd month we realized it wasnt all her so we put one on him as well. No problems since. You can get the right at the pet store.

  5. My male cat who i recently adopted beats up on my other male cat . The agressor is so sweet to me and loves to lay on top of me. The other male is very sensitive and wants to avoid all confrontations especially from the agressive one. Does the boarmate work on both male cats. Does it go on the submissive cat? The agressive one gets beat up pretty good but he keeps attacking the other one regardless. So do i put boarmate on the bully or on the sensitive cat in hopes the bully stops chasing him and fighting? I am tired of taking my bully to the vet for infected bites

    1. I have an issue where the younger cat is trying to mate with the older male cat. The older male is introverted but now he’s retreating. I hope it will work; maybe I’ll consult the vet and then it

  6. My almost 12 year old neutered male cat is going after the other neutered male cats in the house. He was neutered at 6 months, as were all the others. He actually “raped” one of the other males last summer and injured him. That cat is now staying in the back room (his choice) and only comes out to eat. Now the aggressor is going after the other nearly 12 year old neutered male. These two have been raised together since they were about 8 weeks old. So far I’ve been able to stop the unwanted behavior with a water spritz bottle, but I will be returning to work after Christmas and will not be monitoring his behavior almost every moment. What can I do to stop this behavior? I don’t want him injuring this other cat; they are like brothers.

  7. It’s funny how all the comments are from 2017. I am going to try to find some of this Hog Mate Boar spray. I just read a comment about a lady who applies Hog Mate to a cotton ball and then rubs it on the rump and tail area of her female cat every three days and now the male plays normally.
    I always wondered why my cats fight sometimes. Yesterday I saw the male trying to mate with the female. (they are both fixed) She gets really angry at him and he just continues. I have to chase him away but now I’m going to try this Hog Mate stuff.

  8. This stuff is impossible to find, and it sucks that this person doesn’t answer anyone’s comments. “Oh hey guys I may have found answer to your problem that is stressing you out, costing you thousands of dollars in vet bills. Heh, butttttt I’m just just going to ignore everyone and not tell you how to get this stuff that will most likely stop your problem ✌🏼” this person is a giant cock lol just like my neutered male cats corkscrew penis

    1. Hiya there,

      Apparently, if you look it up, it’s available for livestock. This may not sound ideal, but try checking sites like Farm and Fleet. 🙂

  9. I can’t find an answer to my question by googling so hopefully someone knows something here. Our male neutered cat is showing sexual aggression to our spayed female cat. The problem is he’s not biting her scruff, which is normal, he’s wrapping his mouth around her (considerably smaller) neck. This worries me a lot because it looks dangerous and makes me wonder if it’s actually sexual or if it’s just play aggression gone violent. Does anyone know?

  10. I have a neutered male cat that tries to mate with my unnuetered female because she is in heat. Is the unhealthy for either, physically or other?

    1. Please reread the article. Your male is still male, just with less testosterone. As long as the female is not spayed, your male will do this.

  11. I wonder if this stuff will have any lasting effects on the females that it is being put on. Obviously cats are very tedious about cleaning themselves, so when the females ingest this stuff every day while licking their fur clean, what is it going to do to their hormone systems?

  12. Is there any normal way to stop the aggression? I can’t put up with this behavior. My large neutered male is seriously hurting her. She is spayed. Or is euthanizing my only alternative? He is a great cat otherwise.

    1. Or rehome? I never understand how people can go straight to euthanizing as an option in cases like this. I myself am going through this and would NEVER consider that an option.

    2. Try getting hormones from vets for him to sort out testosterone and keeping apart when ur not there and when u are keep eye out

  13. My 4.5 year old male Maine Coon loves to play with our 3.5 year old female Maine Coon, but often, I witness him going in for the nape-of-the-neck bite. He also tends to bite her near her hind quarters or on her head. I don’t think he ever seriously hurts her, but she’s definitely annoyed by it. They’re both fixed and are not related. They are a bonded pair and definitely love each other (groom each other, sleep by each other, eat together, etc.), but our male can get a little crazy with this biting. He seems to be obsessed with her scent, like you mentioned. I may try this spray! I am sure our female would appreciate it 🙂

  14. I just had my two 6 month old male (brothers) cats neutered yesterday. Today they are unhappy as they have cones to keep them from licking their wounds. One of them will not leave the other alone, doing the neck biting, pin down of mating. His brother does not like it and cries out. He had started this behavior a couple of weeks ago, but today he is relentless. I’m trying to keep them separated, but am concerned about this behavior and worried it will be an ongoing problem. Why would he be so sexually aggressive now, especially with a male? Anybody else have this happen?

    1. It’s happening because he’s started to sexual mature, best thing is to keep them apart for a few weeks for his hormone levels to go down, else he might seriously hurt the other as they can get really nasty to other males during this time

  15. My approx 7 year old neutered male was neutered 2 years ago when I brought him inside. He had been the neighborhood Romeo for years. He gets along well with my 3 spayed females but lately he has been chasing the one causing all hell to break lose. She screams, the fur flies but I don’t think he has actually touched her. He will not be stopped from pursuing her either despite my running after him and yelling. He only does it to the one female, probably because she is more submissive. Hopefully I can find this spray!

    1. O please tell me where I can obtain Boar Mate.
      Forever grateful
      Ann Stotts

      Please just give me an answer and forget the robot game

      I have a diabetic cat who isi I’ll and would like to protect her.

      6:30a.m. Insulin shot comes early


      1. Ebay! Costs about £16.00 from Hong Kong with free postage to the UK. Or can be got from the USA, with expensive postage to the UK. My normally lovely docile male cat 6 years old neutered has suddenly started sittin on top of my 3 year old neutered female and biting her neck. Smudge is a fiesty wee girl at times. Mostly they get on like a house on fire. This new behaviour is recent, they are indoor cats. This is the first time I have ever experienced this behaviour with neutered cats, and I do not like it.

          1. ps they are indoor cats, but I have never experienced this behaviour in all the 40 years of having cats.

  16. My neutered male cat thinks I am a female cat. After petting or combing him he gets that look in his eye and then jumps me. it’s a little scary. I was thinking of using a calming collar on him. What can i do, will he out grow this. He was neutered between 9 mos. and 1 yr. he will be 2 yrs in May. thank you

  17. My Male neutered cat has shown this behavior only after getting fixed. He doesn’t care if the other cat is female or Male. I got him at 2 months and neutered him at 6 months. He has ALWAYS been an indoor cat and had never shown this behavior previously. Sugestions?

  18. Im having trouble with a 2 year old male who was neutered when he was about 1 year old. He is harassing my 15 year old neutered male.the younger male will attack the older one every oppirtunity, even going as far as searching him out to corner him for hours. Recently the younger male has begun grooming the older male though and i thought the fights and harrassment were done, but now the young male will groom my old male and without warning clamp his jaws down on his throat. Not the back of his neck, his throat. And he will pin him there until somehow my older male gets out of his hold, or someone walks in the room. The younger male scares easily at any noise, yet he is constantly harassing and attacking my old male. I dont know what to donor if this is normal, it doesn’t seem normal to me as the biting is very aggressive and malicious, to the point where my older kitty has trouble breathing. Help!

  19. We have a 1 year old black, neutered female [LG] and a neutered male [Bob] who is about 2. We introduced them to each other when the female was a kitten. They got along well from the beginning with the male acting like a tolerant big brother. They love to chase each other and the Little Girl appears to adore her ‘big brother. Both cats were tolerant and curious when we house sat a visiting Boston Terrier for a few days.

    BUT, last week we hosted a young female and both cats took an instant dislike to her, despite her obvious desire to be friendly and be near the others.

    We finally figured out the new one, ‘Cookie,’ contrary to my wife’s niece’s claim, had not been spayed. After a couple days it became clear Cookie was ‘in heat’ for the first time. Tho’ we separated Cookie from the other two, she stayed near the separating door, howling. When I opened door, Bob, despite being neutered, grabbed Cookie by the neck and appeared to try to mount her. Cookie appeared receptive tho’ it was an exercise in frustration for both. Fortunately we were able to return Cookie to the niece who reported more howling. Obviously, the niece needs to have Cookie spayed.

    So, what is going on? I didn’t realize neutered males would still react to the pheromones an uneutered female puts out. I am also supposing those same pheromones were the cause of the hostility.

  20. It’s a shame there are no answers here. We have had endless trouble with our 5yo, early castrates boy. Our two girls keep escaping and going missing because he is so rapey. We tried Boar Mate 3yrs ago with no success and for the last 2yrs have been giving him the human female contraceptive Depoprovera every 6mths. His behaviour has not been affected this last injection. It was his last chance, as we boarded him for a week to let the girls come and get familiar with their surroundings again. The last straw was him biting and humping my poodle bitch until he drew blood

  21. Well apparently after reading the article, I’m not alone in my frustration regarding my neutered male still acting like an intact Tom cat!
    My sympathies to EACH of you who know THIS HELL!
    My spayed 5 year old female comes in and out at will. My neutered year and a half old male has to stay inside because he’s terrified of the outdoors or I’d let him outside too. 😭 I love all of my babies and they are spoiled rotten all 3 dog’s and both cats! But I’ll NEVER have another Male furbaby EVER! 😥

  22. I’m having trouble with a 1 1/2 year old male, neutered at about 5 months of age, going the the motions with my 7 month old male kitten, who was also neutered at about 5 months of ago. There are three other cats in the house, another male and 2 females. All fixed and ranging in age from 5 to 13 years. He doesn’t try this with any of the other cats. WTH??!!! And it’s getting worse by the week. They play together awesome, sleep and eat together, never far apart from each other. I don’t want this to affect the bond they have. Any suggestions? Would this Boar stuff work male to male?

  23. I have two male cats that were neutered a few days ago. Prior to the operation they were the best of friends. I have three cat beds but they shared the same bed and even groomed each other before the surgery. Now the orange cat chases the black cat. And the black cat backs away from the orange when they get close. Whats going on with them. I want them to be the best of friends that they were. Oh I should mention that there was a third grey cat that I returned to my brother because he was fighting with my cats.

  24. Was truly hoping this would work. I adopted two 8 year old sibling Himalayans: the male looks Siamese and the female more Persian. They are adorable. the female bats and growls her brother away if he gets too close. We have an older female Tabby and he simply wont leave her be. He follows her everywhere, cries if we lock her in a separate room for some piece, as cries as well if we tell him to go into another area of the house. Bought the boar’s mate. Worked one day, now no effect whatsoever. I was extremely disappointed thought this would bring harmony to the family, but alas I guess his hormones are still raging. Off to the vet for further examinations and suggestions later this week.

  25. ok…but what do you do if your neutered male cat is trying to mount another male? I have two cats, the older one is neutered and the younger one isn’t yet. They’re both males, but I’ve seen the neutered one trying to mount the other one! How is this possible?

  26. I am going to try this. My female 13 year old is constantly being bitten and mounted by our 13 year old Bengal. He is out of order and we physically have to prise his jaws off her . He’s increasingly making her life miserable.

  27. My 7 month male isn’t neutered until next month. He just became aggressive towards me. He wasn’t brutal, but, kept trying to get around me to my back. He grab my arm and bite it while holding on. It scared me at first, but, is that perhaps his hormones kicking in? I have a female that’s spaed and I petted her prior. This is very first time he has done anything aggressive or weird. I really hope it’s hormonal. Then, next month, that will subside. I’ve never had a male cat, only females. So, this is alarming.

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