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Feature January 2014 Issue

Sexual Aggression in Neutered Cats

Even a neutered male cat can make life miserable for his female housemate. And fighting with neighborhood males can persist, too. Here's why.

Unless you’re planning to breed your male cat, there are several very good reasons for you to have your pet sexually neutered at some point during the first six months or so of his life. Most importantly, the procedure will prevent his contributing to the worldwide problem of feline overpopulation.

Neutering will also eliminate or at least reduce the occurrence of several undesirable sex-related behaviors. These include, for example, roaming, scrapping with rival male cats in the neighborhood or in your own home; staking out territory by spraying foul-smelling urine throughout your home and property; and persistently attempting to mount and sexually engage a female cat in the household, whether or not she is willing to cooperate.

Some of these sex-related activities, however, may persist even after a cat has been neutered. The male sex hormones — chiefly testosterone and its derivatives — tend to start being secreted when a cat is four to five months of age, and the animal will begin to show an interest in females two or three months after that.

Neuter Your Cat By 6 Months Old

“That’s why we recommend that a cat be neutered by the time he is about six months old,” says Nicholas Dodman, BVMS, director of the Animal Behavior Clinic at Tufts. “If you let a male go unneutered, he’ll have a lot of testosterone circulating in his body, and he’ll continue to be very interested in females. He’ll smell a female in heat from several blocks away, and he’ll be very eager to get out of the house and go after her. And if he’s not allowed to go outside, he is likely to start humping something else, such as a stuffed toy, a table leg, a pillow — anything he can get at.”

Until months or even years go by, a neutered male cat may continue to express himself sexually with a female cat living under the same roof, even though she has been spayed. “He sees this female wandering from room to room,” says Dr. Dodman, “and he’ll run after her in the same way he would in a true mating sequence.” He describes what happens next in a behavior pattern motivated by what he refers to as residual maleness: “The female will be terrified. She’ll run and try to hide. But the male cat finally jumps her from behind, and there’ll be fur flying. And then he’ll bite into her neck, drag her to the ground, pin her there, and may even attempt to mate with her.”

Although neutering gets rid of various unwanted behaviors — including rapacious mounting activity — in 90 percent or so of male cats, Dr. Dodman notes that about 10 percent of cats will continue to display the behaviors. Some of these cats will also go on spraying urine as a means of marking their territory for a period of time — perhaps permanently — following the procedure. “So owners should know that, in some cats, neutering does not completely turn off the sexual lights,” says Dr. Dodman. “Instead, the procedure sort of turns the dimmer switch way down, but there’s still enough of the male behavioral instinct remaining to be problematic.”

This variety of feline sexual harassment poses little if any threat to the physical well-being of the assaulted female, he points out. But it can certainly be psychologically damaging to her, making her constantly wary, nervously in fear of her male companion’s next attack. “It disrupts the household,” says Dr. Dodman. “You don’t want to go on living in a place where a female is constantly afraid of being attacked. That’s havoc, and that’s why a cat owner should make every effort to curb this behavior.”

Medication Can Help Sexually Aggressive Cats

An array of pharmacologic interventions are available that may be effective in reducing a neutered male’s inclination to assert sexual dominance. However, advises Dr. Dodman, before trying any of these pharmaceuticals, it would be worthwhile to have an offending male cat examined to make sure that the neutering operation that he underwent was performed properly.

It is possible, he says, that, during the operation — due to an oversight by the surgeon — only one of the cat’s testicles was removed. If that is the case, an injection of a hormone called gonadotropin-releasing hormone (GnRH)) will reveal the presence of any residual testicular tissue by causing a surge in testosterone. “This is very rare,” Dr. Dodman notes, “but it does happen. Sometimes, for example, one testicle was in the normal location but the other was in the abdomen, inaccessible to the normal neutering procedure.” Ultrasound can also be used to make the diagnosis.

If it is determined that a cat was successfully castrated, the pharmacologic substances that may be helpful in curbing his persistant sexual aggression include clomipramine and fluoxetine, which can reduce the obnoxious behavior.Although such drugs are gaining popularity for the suppression of unwanted sexual drive, they must be used only under the careful supervision of a veterinarian.

Dr. Dodman sometimes uses fluoxetine to treat overzealous male cats, but he sometimes opts instead to use topical androsterone, a pheromone produced by males, on the females in the household. He explains: “If you apply this pheromone to a female cat’s rump every other day or so with a small cloth and a male approaches her, he’ll suddenly stop short, arrested by this powerful scent of maleness, and he’ll turn away as if to say ‘Oh, excuse me, sir … I must have confused you with someone else.’”

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