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Help, My Dog Is Aggressive After Being Neutered!

Adrienne is a certified dog trainer and former veterinarian assistant who partners with some of the best veterinarians worldwide.

Is your dog aggressive after neutering?

Is your dog aggressive after neutering?

Is Your Dog Acting Aggressively After Neutering?

If your dog is aggressive after being neutered, you are likely wondering about what could have caused this sudden and unexpected behavior change.

Before blaming the procedure and regretting your choice, consider that there are several potential factors at play and some behavior changes can be temporary.

In this article, veterinarian Dr. Ivana Crnec will discuss what neutering surgery entails and will then go into depth on what can cause a dog to become aggressive following surgery. Dr. Ivana will also discuss what recent studies show about aggression levels in dogs after neutering procedures.

A Dog's Neutering Surgery Explained

Up until recently, the general rule of the thumb was that all male dogs excluded from breeding programs needed to be neutered.

The procedure was recommended because of its positive impact on decreasing the risk of various diseases and prolonging the dog’s life.

However, newer studies suggest the potential link between neutering and certain types of aggression.

Before discussing how neutering may trigger some behavior changes, let's first take a closer look into the procedure.

Neutering is a surgical procedure that describes the removal of the dog’s testicles. It is considered a routine procedure, performed under general anesthesia, and by a licensed veterinarian.

The neutering procedure is a low-risk operation, in fact, there is more risk associated with the anesthesia rather than the actual surgery.

The ideal neutering time for a male dog is between six and nine months old. However, the procedure can be performed at any point, starting as early as eight weeks old.

Neutering affects male dogs at various levels. Neutered males have decreased risk of developing testicular cancer and prostate disease. They are also less likely to roam and wander, rarely urine-mark inside the house, and do not hump on other dogs.

Does Neutering Change a Dog's Personality?

A big question many dog owners ask is whether neutering changes a dog's personality. While certain behavioral traits and habits do change with neutering (for better or for worse), the general personality (basic temperament and intelligence level) of the dog remains the same.

For some dogs, it is possible to get depressed following a neutering procedure. However, these feelings are self-limiting and often associated with stress and pain. In most cases, the depression is fully gone a day or two after the procedure.

Neutered dogs can completely finish their recovery period and get back to full and normal activity in as little as two weeks.

If your dog is aggressive after neutering, you are likely concerned about this abrupt behavior change.

If your dog is aggressive after neutering, you are likely concerned about this abrupt behavior change.

Myths About a Dog's Neutering Procedure

There are many myths surrounding the neutering procedure. Indeed, these myths are still quite popular and are hard to die. Below are several common myths.

  • Myth: Neutering makes dogs sad and depressed.
  • Myth: Neutering will make dogs gain weight.
  • Myth: Neutering makes dogs feel less manly.
  • Myth: Neutering is dangerous.
  • Myth: Neutering is an expensive procedure.

However, the most popular myth revolves around the widespread assumption that neutering can help solve all behavioral problems in dogs.

In fact, many people believe that neutering has a positive impact on aggressiveness.

The truth is, neutering does decrease certain aggressive behaviors, but on the other hand, it tends to increase the intensity of others.

Castration was most effective in altering objectionable urine making, mounting, and roaming. With various types of aggressive behavior, including aggression toward human family members, castration may be effective in decreasing aggression in some dogs, but fewer than a third can be expected to have marked improvement.

— Neilson, J & Eckstein, R & Hart, Benjamin. (1997).

Understanding Aggressive Behavior in Dogs

According to the ASPCA, the American Society for the Prevention of Cruelty to Animals, the term “aggression” refers to a wide variety of behaviors that occur for a multitude of reasons in various circumstances.

It encompasses an array of behaviors ranging from growling and lip snarling to attacking and biting. Different dogs express aggressiveness differently and with varying intensity.

Regardless of the expression form, aggression always stems from feelings like fear or anxiety and the innate inclination to protect and guard.

There are different forms of aggression in dogs, including:

  • Territorial aggression
  • Protective aggression
  • Possessive aggression
  • Fear aggression
  • Defensive aggression
  • Social aggression
  • Frustration-elicited aggression
  • Redirected aggression
  • Pain-elicited aggression
  • Sex-related aggression
  • Predatory aggression.

These different forms of aggression can be expressed towards family members, strangers, or other dogs and pets.

The most common trigger for aggressiveness in dogs is fear. It can stem from inadequate socialization or negative experiences (abuse and neglect).

Can aggressive dogs be retrained? Yes, it is definitely possible to retrain and successfully manage an aggressive dog. However, the process is long, challenging, and requires the help of trained professionals – canine trainers and behaviorists.

It is important to remember that aggression is not a disease and therefore it cannot be cured. It is best to consider it as a specific condition that requires permanent management and close collaboration with vets, trainers, and dog behaviorists.

Why is My Dog Aggressive After Neutering?

There are three possible reasons for a dog to act aggressively after neutering. The first two are transient and resolve over the course of several days, while the third is more permanent and requires professional help.

Vet visits are stressful for most dogs. While some dogs respond to the trigger with shyness, others respond with more pronounced aggressiveness.

If a single vet visit can be stressful, imagine the impact of the overall neutering procedure—spending the whole day, or possibly, even the night at the vet’s office.

It is not uncommon for dogs to feel pain or at least discomfort after surgical interventions.

Pain is the reason vets prescribe painkillers for dogs after neutering. However, despite the pain management, some dogs may feel uncomfortable and this is an objective reason for acting abnormally.

3. Hormonal Changes

Testosterone is directly associated with certain forms of aggression. Once removed, the overall chemical makeup changes which can lead to altered habits and behaviors.

Since testosterone affects only certain forms of behaviors, its removal does not result in a non-aggressive dog.

A more careful examination of the aggression with a veterinarian experienced in treating behavior disorders is now recommended prior to neutering, as neutering may worsen fear-related behaviors in a small subset of dogs.

— Debra Horwitz & Gary Landsberg, veterinary behaviorists, VCA Hospitals


Undoubtedly, neutering your dog comes with a myriad of benefits, from decreased risks of certain types of cancer and prostate enlargement to managing behavioral issues like urine marking indoors and howling when left alone (Source: McGreevy PD, et al. 2018)

However, the neutering procedure has a list of cons too. Sadly, the biggest issue associated with this procedure is the increase in specific forms of aggression. This does not mean though that every neutered dog will become aggressive, however, the risk is worth mentioning.

If you plan on having your dog neutered, consult with your trusted veterinarian and carefully compare the pros of the procedure with the cons. In most cases, the list of pros is much longer and outweighs the potential cons.

Dogs who were neutered at less than 12 months had the highest levels of aggression with dogs neutered at 13–18 months being the closest to the intact dogs in aggression level. In addition, fear and anxiety was significantly higher in groups of dogs who were neutered when compared with intact dogs. (Source: Farhoody & Zink 2010)

— Lisa Radosta, veterinary behaviorist, VIN (Veterinary Information Network)

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2021 Adrienne Farricelli