(First published March 2005 in The Mayor’s Alliance for Mayor’s Alliance for NYC’s Animals newsletter, Out of the Cage!)

First, here are some facts:

Spaying refers to the surgical procedure for females by which the uterus and both ovaries are removed (ovariohysterectomy). The same term applies to both dogs and cats, and the procedure is essentially the same for both. Because the organs are within the abdominal cavity, there will be a midline incision below your pet’s “belly button.” Once your pet has had this procedure, she is considered spayed (not spaded — a common misconception).

Neutering usually refers to the surgical procedure for males by which both testicles are removed (castration). The procedure is slightly different for dogs versus cats. Dogs will have a single incision below the scrotum. Cats will have two tiny incisions on the scrotum itself. In both cases, the scrotal sack remains completely intact. With normal post-operative swelling, it might even look like the testicles are still there, but eventually the sack will shrink and become barely noticeable. Neutering is occasionally used in a broader sense to describe surgical sterilization of either males or females.

Why Spay and Neuter? So many reasons!


Intact, or unspayed, females have a seven-fold higher risk of developing mammary tumors. They also have a risk of developing a uterine infection later in life, which can be serious — even life threatening.

Intact, or un-neutered, male dogs are more likely to develop prostate problems later in life than are neutered dogs. If there is a testicle that remains in the abdomen rather than descending into the scrotal sack, it can become cancerous. Dogs also can develop testicular tumors.

Social well-being

Neutering a small-breed male dog will reduce the chances of dangerous or deadly attacks by larger dogs.

Neutering a small-breed male dog will reduce the chances of dangerous or deadly attacks by larger dogs.

Intact female dogs will attract uninvited attention from male dogs while they are in heat. Cats are seasonally polyestrous, which means that once an intact female comes into heat, she will continue cycling until bred. During this time there will be excessive (often extreme) vocalizing and posturing, which can be unpleasant for the cat and her human.

Neutering a small-breed male dog will reduce the chances of dangerous or deadly attacks by larger dogs.

Neutering a small-breed male dog will reduce the chances of dangerous or deadly attacks by larger dogs.

Intact male dogs have more issues with aggression, whether they are the instigator or the target. I emphasize this point very strongly with clients who live in the city, especially those who have small dogs. Much of our social activity takes place at the dog run or daycare, and it is all too common for a large-breed dog to attack an un-neutered small dog (no matter how friendly he is). Bite wounds are frightening and can be quite costly, even if they appear minor. Some cases of BDLD (Big-Dog-Little-Dog) are deadly. Male dogs of any size who are not neutered tend to exhibit more of the unpleasant sexual behaviors, such as “humping.”

Male cats who aren’t neutered will develop a strong and unpleasant odor to the urine as they become sexually mature (usually around eight months). At about the same time, many will start to mark their territory by urinating outside the litter box. Once this behavior starts, it might not be easily reversed. Intact male cats who are outdoors are more likely to get into fights with other cats, which in turn can spread disease into the population.

Pet Overpopulation

The idea of puppies and kittens is always appealing, but there are far too many animals living in shelters or being euthanized due to overpopulation. Rather than let your pet procreate (intentionally or accidentally), adopt one who needs a home!

There is a fair amount of folklore, often generated by fanciers of the various breeds, regarding when to spay or neuter. The only real evidence we have (as far as health benefits go) is that there is a lower risk of mammary cancer if we spay before one year of age. Most veterinarians recommend spaying and neutering at six to eight months, as there is no known benefit to allowing a heat cycle.

Many shelter programs are safely neutering and spaying as early as seven weeks to prevent pet overpopulation with careless pet guardians. Despite speculation that early surgery might contribute to stunted growth, behavioral changes, or urinary incontinence, several studies have found that skeletal, physical, and behavioral development, as well as urethral function, are affected equally by early versus traditionally timed neuter.