Although neutering can alter a lot of behavioral elements in a cat, the surgery can't necessarily change everything, whether humping or an occasional bout of nonstop yowling. If your cat has developed a rather awkward and persistent mounting habit, neutering may definitely minimize the action, but definitely with no promises.
Neutering surgery entails the extraction of the testicles, and therefore decreases a tomcat's testosterone levels greatly. With significantly lower amounts of testosterone, a male cat, simply put, will not be driven by raging hormones in the same manner as before. Without the strong desire to mate, a cat may indeed cease actions such as mounting and humping stances, trying to escape from the home, urine spraying, yowling all throughout the night hours and acting out aggressively.
If your neutered male cat still has the desire to mount random things and individuals, whether your living room armchair or another pet in your home, don't be shocked. The Baltimore Animal Rescue and Care Shelter indicates that the surgery reduces the behavior, instead of entirely eliminating it. Although it may not make your cat totally stop, it at least may curb the behavior a bit.
If a male cat continues to hump even after being neutered, it may be because he is still, bizarrely enough, capable of mating and reproducing. In fact, it takes a little while for the hormones to make their grand exit out of a tomcat's body. The East Bay SPCA indicates that a male cat may actually be able to impregnate a queen for a maximum of six weeks post-neutering -- yikes. Remember, male cats still may be able to father litters immediately after surgery, so keep them away from unspayed female cats for a while.
Age of neutering may affect a cat's post-neutering behavior. If a male cat is neutered at an early age -- say before 6 months -- then he may never develop hormonally-charged behaviors such as humping. However, cats neutered at a later date may actually retain some of these types of behaviors out of habit, even after neutering. Speak to your veterinarian about the smartest, safest and most sensible time frame for neutering your precious cat.
In the case that your male cat's humping doesn't appear to be subsiding at all, consider the remote possibility that his neutering surgery may not be fully complete. Take your cat to the veterinarian to check if this, indeed, is the situation.