Does Neutering Affect a Dog’s Behavior?

“Neutering” is the medical term for spaying a female or castrating a male dog or cat. There are many ways to perform neutering for companion animals, and in most cases, all reproductive organs are removed.

Neutering began as an effort to combat pet overpopulation and increase health benefits. And while neutering dogs can decrease the risk of ovarian and breast cancers, prostate disease, and pyometras, it can also decrease or even eliminate socially unacceptable behaviors in dogs.

What Is Neutering?

Neutering is the scientific term for removing the reproductive organs of an animal. It’s commonly referred to as “spaying” for female dogs and “castration” in males.

The procedure is performed by a licensed veterinarian and is considered a routine preventative procedure. Along with preventing unwanted dog pregnancies and litters, neutering can prevent clinical illnesses including:

• Cancers (ovarian, breast, and prostate)

• Hormone-induced diseases (pyometras, false pregnancies)

• Infections

Neutering may occur at different ages based on many different factors, such as breed, age, temperament, and how you acquired your pup. Talk with your vet about the best time to neuter your dog.

How Neutering Affects Dogs’ Behavior

Intact dogs (those who have not been neutered) can have a wide range of behaviors that occur due to the fluctuations in their hormone levels. Along with the health benefits, many of the behaviors that people find socially unacceptable in dogs decrease drastically with neutering. This includes:

• Aggression toward other dogs: Aggression in male dogs will decrease by more than half with altering.

• Roaming behaviors: Both male and female dogs have a decreased roaming distance and desire to roam after neutering, which helps reduce the risk of accidents (such as being hit by a car) or getting lost.

• Marking: Neutering a male dog before marking behaviors begin eliminates the behavior to almost 2%. However, if you neuter an older dog who has already begun marking, it might be more difficult or impossible to modify the behavior. 

• Mounting, humping, and increased sexual drive: These behaviors are drastically reduced by more than 50%.

These behaviors are reduced because neutering decreases reproductive hormones (testosterone and estrogen) in your dog. But it’s important to remember that, even with neutering, hormones are still present in the body—they just don’t fluctuate as they would with intact reproductive organs.

As with any behavior, there are many influencing factors, and neutering is not the only one to consider. Breed, genetics, susceptibility to certain behaviors, and medical conditions should also be taken into account.

It’s not just undesirable behaviors that are affected by neutering. The risk for weight gain also rises—not because of decreased activity, but because of a biological process that occurs after neutering. A dog might feel hungrier due to changing hormones, but in reality, they need fewer calories than their craving suggests.

Hormonal changes affect both male and female dogs, but as with any procedure, the effects can be different.

• Territory aggression: The drive to defend personal space from friend or foe. This behavior typically occurs along a property line or, sometimes, in your pup’s home. This behavior is rarely seen in puppies and usually occurs as reproductive hormones are released in adolescence.

• Socially unacceptable behaviors: Roaming, marking, and mounting.

• Roaming/escaping: Hormones play a large role in the drive to reproduce, leading dogs to escape to find a partner. Intact dogs not only have a higher chance of roaming but also roam greater distances.

• Marking: This is a distinctive behavior attributed to sexual hormones. It occurs to either show other animals that a dog is seeking a partner or that a partner has been claimed.

• Mounting: This behavior increases with sexual drive and occurs during excitement in many dogs. This behavior becomes more learned the longer a dog is intact.

• Aggression towards other dogs: There are many reasons why dogs display aggression towards other dogs, but sexual hormones play a role in the intensity and duration of these events. Same-sex aggression is higher in male dogs who are not neutered.

• Hyperarousal: This behavior occurs when excitement becomes heightened. Sexual hormones can increase the behavior.

• Resource guarding: As with aggression, resource guarding can occur for various reasons, though it can be more frequent with intact animals.

Keep in mind that, while these behaviors can be modified or even diminished with neutering, some behaviors are learned. Neutering might decrease these behaviors, but completely eliminating them may require behavioral therapy.

Should You Neuter Your Dog?

Neutering dogs and cats is the only way to completely prevent unwanted pregnancies. But more than that, the procedure also improves the overall health and behavior of your pet.

When considering whether to neuter your dog, talk with your veterinarian. Your vet can help conduct a risk assessment and will work with you to determine your dog’s risk factors so you can address health and behavior concerns.

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