Will neutering a dog help with aggression?


Castration is a surgical procedure that can be performed for several purposes. Can castration change a dog’s aggressive behavior? To answer that question, this blog article will talk about the behavior change of dogs after neutering.

Will neutering a dog help with aggression?

Yes. We can say that castration can be used as a method to reduce aggression and some sexual behavior desorders in dogs.

In a 1997 survey, Maarschalkerweerd and colleagues demonstrated a reduction in dog aggression after neutering and only a few dogs had no change in behavior. Indicating that testosterone would influence the aggressiveness of dogs. 

With the reduction of testosterone and libido these animals tend to reduce the territorial demarcation and thus become more calm and friendly to other dogs of the same sex.

Aggressivity can be linked not only to the hormonal characteristics of dogs but also to learned behaviors. For example, an abandoned dog that had to use aggression to protect its territory on the street and fight for food, when neutered tends to remain aggressive as a form of defense.

Why is castration important for dogs?

Castration is a very widespread surgical practice among veterinary clinicians, but with few discussions about the benefits and the real recommendations, disadvantages, and contraindications. Below are some of the benefits and harms of castration.

Benefits of Castration:

  • Population control;
  • Prevention of breast tumor;
  • Prevention of pathologies of the reproductive system such as pyometra, endometritis, benign prostatic hyperplasia;
  • In some dogs it can reduce territory demarcation and aggression.

Population control

Castrated dogs do not reproduce, thus helping with population control. Abandoned dogs can benefit more from this practice, while tutor dogs will never reproduce even if they are not castrated, requiring an evaluation with the veterinarian to make the best decision for the animal’s health.

Population control is very necessary due to the large number of abandoned dogs. Abandoned dogs without castration can generate many offspring and thus only exacerbating the problem by increasing the population of abandoned dogs. That’s why it’s important to perform castration, especially in abandoned dogs.

For tutor dogs, it is recommended to consult the veterinarian to assess the need for castration. If it is an animal that runs away a lot, it would be interesting to keep it castrated, avoiding problems with unwanted reproduction.

On the other hand, Molento and colleagues in 2007, show in their research that castration alone is not enough to help with population control. To be a real solution to the uncontrolled dog population problem, a mass castration must be associated with the education of the population for responsible dog care.

Tumors prevention

In female dogs, spaying can reduce the chances of breast tumors. Some breeds, especially small breeds, are more predisposed to develop breast tumors. For these breeds, a consultation with a veterinarian for spaying is indicated.

In males, castration can prevent the benign prostatic enlargement that affects elderly male dogs. Care must be taken because recent studies show that neutering can bring some harm to dogs. Therefore, castration must be a joint decision between tutors and veterinarians.

Prevention of genital tract diseases

In female dogs, diseases such as pyometra, endometritis, uterine tumors, ovarian cysts and others are no longer a concern. In the surgery, the uterus and ovaries are removed, so the animal will not have any of these diseases.

In males, testicular diseases such as orchitis, testicular torsion and tumors are no longer a problem since the testicles were removed from the dogs, thus preventing the occurrence of these diseases. Prostatic hyperplasia in elderly dogs can also be avoided with dog castration, due to the reduction of circulating testosterone.

It is important to remember that cryptorchid dogs have a high chance of developing a tumor in the ectopic testicle, so neutering dogs with this disease is always indicated.

Behavioral changes

Castrated dogs tend to be less energetic so they reduce physical activity and play. But not all dogs are like that, some continue to show active behavior.

Therefore, after castration, the use of food for neutered dogs is indicated, thus avoiding the animal’s weight gain associated with the reduction of physical activities.

Without sex hormones, dogs reduce libido, thus reducing unwanted sexual behaviors, such as mounting behavior on visitors, other dogs and even objects. Territory demarcation also tends to reduce after castration.

Aggression tends to decrease in male dogs, but some female dogs may exhibit more aggressive behavior. However, it can be related to dogs that have already suffered some trauma, or to breeds that are naturally aggressive.

Dog behavior can be learned at the puppy stage and even at puberty. These learned behaviors can remain even after castration. Castration can reduce some behaviors in some dogs and even solve unwanted problems, but castration is not a sure solution to dogs behavior problems.

Harms of castration:

  • Increased occurrence of tumors such as osteosarcoma, hemangiosarcoma and others;
  • Increased incidence of orthopedic diseases;
  • Increased the animals weight gain.

Recent studies point against castration, such as the possibility of increased risk of orthopedic problems, possibility of recurrent vaginitis, obesity, increased incidence of some tumors such as hemangiosarcoma, osteosarcoma, among others, in addition to the risks of surgery itself, including problems with anesthetics.

Even knowing the benefits of castration for dogs, its harm must be considered. Tutors and veterinarians must agree on the animal’s general health status, tutor’s breeding intent, breed, age and location. 

Thus, the veterinarian can help the tutor in the decision to neuter or not and when to neuter the dog, in order to avoid health problems for the animal.


With this article we were able to understand that some dogs will become less aggressive after neutering, but others will not. Aggression is related not only to the sex hormone but the ability to learn and deal with a certain behavior. Finally, it was also presented a little about the benefits and harms of castration and how important it is to decide for castration with veterinary help.

Frequently Asked Questions (FAQs): Will neutering a dog help with aggression?

How does the castration procedure work?

The castration of the male is called orchiectomy and the removal of the testicles of the animal is done. In this way, there is a suppression of sperm production and the production of hormones such as testosterone.

In females, the surgery is called ovariohysterectomy, where the ovary and uterus are removed. In this way, the suppression of the production of sex hormones such as estrogen and progesterone occur.

Neutered female dog comes into heat?

No, this is because castration removes the internal reproductive organs responsible for inducing heat. In this way, it is not possible for a castrated female dog to show heat. If the female dog is in heat a possible disease called remnant ovarian syndrome should be investigated.

What are the benefits of neutering a dog?

The benefits of neutering a dog are:

  • Population control;
  • Prevention of breast tumor cases;
  • Prevention of pathologies of the reproductive system such as pyometra, endometritis, among others;
  • Prevention of benign prostatic hyperplasia;
  • In some dogs it can reduce territory demarcation and aggression.


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