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.


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.

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.

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.

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. 

24 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?

  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.

  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.

  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

  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

  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?

  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.

  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?

  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!

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