Can Hormones in Male Cats Cause Them to Be Aggressive?

Neutered male cats are typically significantly less aggressive than intact males.
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If you own an unfixed male cat and he's constantly getting into physical fights with other tomcats in your home or in your neighborhood, his behavior probably isn't much of a surprise. With hormonally influenced cats, aggression is the name of the game, whether it comes to territory or access to females.


Hormones are message-transmitting chemical substances that travel within the bloodstream and regulate specific organs and cells in the body. Androgen is a type of testosterone, a male hormone responsible for managing male sexual traits. Androgen hormones in your fluffy pal can often encourage aggressive, undesirable and even deadly behaviors. With high testosterone levels, male cats are often fiercely competitive with each other, engaging in threatening staring stances, loud vocalization and traumatic physical attacks -- think biting and scratching.


When it comes to hormonally charged tomcat aggression, two of the biggest culprits are females and territory. When a female cat is in season and ready to mate, tomcats will physically fight each other to gain access to her. Such fights can cause major physical wounds and resulting abscesses -- ouch.

Unfixed male cats are also often aggressive with each other due to territorial conflict, even within a household. For example, if you adopt a new cat into a home with pre-existing pets, the older resident felines may begin acting aggressively to display to the newbie exactly who runs the place.


Neutering a male cat usually eliminates -- or at the least greatly reduces -- aggressive hormonal behavioral patterns. The surgical procedure involves the extraction of the testicles. Without testicles, hormonal production ceases, and so does hormonal aggression, usually.

In some cases, it may take a couple of months for a tomcat's aggressive behavior to completely stop. The hormones don't exit the body the same time the testicles do, after all. With time, you may notice that your male cat is significantly more relaxed, mellow and gentle than before. Not a bad deal for you at all.

Other Hormonal Behaviors

Hormones in male cats lead not only to physical aggression but also to various other undesirable behaviors, including restless roaming, loud and persistent vocalization, and urine spraying. All of these behaviors are classic and normal signs of intact, reproductively mature cats. If you remove the hormonal influence in a cat by neutering him, you can often prevent aggression and many other behaviors together.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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