Why is my dog still aggressive after being neutered? What to Know

Does Neutering Change a Dog’s Personality?

A big question many dog owners ask is whether neutering changes a dogs 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.

What Behavioral Changes Can You Expect?

Strange behavior after neutering dog is exhibited in a variety of ways. So, while one dog may gravitate toward their bed and avoid playtime, another may exhibit combative or nervous behavior. Additionally, if you notice strange dog behavior after neutering, don’t ignore the fact that they may be experiencing issues separate from the neutering. To learn more, visit our post answering the question, “why is my dog acting weird?”

Generally, there are four frequently occurring behaviors to look out for:

Additionally, your dog may act more excitable or even confused upon first coming out of the veterinary office. While this behavior may be a short-term result of the anesthesia or pain medication, it could also hint toward a more long-term behavioral change.

Immediately after surgery, dogs are often irritable. It’s easy to imagine being a little testy after waking up from an extended nap, and they often will feel disoriented and confused.

The problems arise when the aggressive behavior lingers for days or even weeks after the surgery. In these cases, this type of behavior may be a result of any of the following:

Post-surgical pain – The vet will administer long-lasting pain killers to keep your dog comfortable after the surgery. These drugs typically wear off after 12-24. However, your vet may also prescribe additional painkillers to give your dog at home. It’s expected for discomfort to last for a few days after surgery but if your dog continues to feel pain after a week, it may be a sign that something more serious is occurring. As such, consult your vet if you notice redness, swelling, or discharge near the surgery site.

Stranger danger – After a stressful surgery, your dog may be a little wearier around people they don’t know. This can manifest as barking at strangers on the street, growling at new people in your home, or even trying to bite you or other house guests.

Male dog issues – Following the procedure, some dogs, particularly those that are male, may have aggression issues around other male dogs. That’s because when a male dog is neutered, testosterone production stops, which may make it difficult for your dog to connect to other good boys.

However, most dog aggression is not a result of hormonal imbalance but a type of fear reaction. Growling, barking, or acting intimidating could be your pup’s way of trying to act tough when they’re actually agitated and panicked.

As such, keep a close eye on your dog in the weeks after their surgery to help identify what triggers their aggressive behavior.

Is your dog spending more time in its bed than usual or are you finding vomit in the living room when you wake up in the morning? Nausea is a frequent post-surgery side effect in dogs as well as humans. As with all puppy health problems it should be closely monitored for the safety of your pooch.

Some key reasons for nausea after neutering include:

Anesthetic – The anesthetic used to keep your dog unconscious and comfortable during surgery can cause some serious stomach problems. These powerful drugs are known to upset puppy tummies and even cause vomiting. It can take several hours for the anesthesia to completely leave your pup’s body. In the meantime, you may have one sick puppy on your hands.

Empty stomach – Your vet most likely asked you not to feed your dog before coming in for the surgery. This preventative measure can also lead to nausea following the operation. With an empty stomach, your dog might try to scarf down a full bowl of food as quickly as possible. Avoid this by providing small amounts of food over a long period until you’re certain the nausea has passed.

It’s normal for your dog to experience nausea the first day after surgery. However, if vomiting persists, you should consult with your vet immediately. Consistent vomiting can lead to dehydration and may be accompanied by abdominal pain, feelings of depression, weakness, and poor appetite.

A dog needs to rest after surgery. While neutering is a minimally invasive procedure that’s performed daily in veterinary offices, it can still take a lot out of a dog. Don’t be surprised if your pup wants to take an extra-long nap or even sleeps through the rest of the day.

But, if your pup exhibits low energy levels for several days following the surgery, it may indicate that something is inhibiting the recovery process. Likewise, there may be an underlying issue if the lethargy begins to manifest in other ways, like:

Depression – Dogs can start to feel down in the dumps for any number of reasons. Depression in dogs often manifests as disinterest in activities they previously enjoyed, such as playing fetch in the backyard or going on walks. Monitor your pup closely. If they’re spending too much time laying on their belly and avoiding their favorite chew toys, you may be dealing with doggy depression.

Disinterest in food – A weak appetite is one of the most common signifiers of an animal in distress. Dogs are typically voracious eaters, happy to chow down on whatever is in their bowl (and whatever table scraps they can get their paws on). If your dog starts skipping meals, it’s time to get the professionals involved.

Judge your dog by how they acted before the surgery. If they’ve always preferred an evening on the couch over an extra-long walk, perhaps their low energy is nothing new. But if your marathon runner pup hasn’t left the doggy bed, it could be cause for concern.

On the other end of the dog mental health spectrum, there’s nervousness and unease. It may surprise you that these people-pleasing, loyal companions deal with feelings of uncertainty regularly, but it’s actually a regular occurrence among furry friends.

After surgery, your dog’s fear drive may be significantly heightened, resulting in problems like:

Separation unease – Is your puppy finding it hard to be alone? After being neutered some dogs suffer from separation unease and are unable to relax without their human companion nearby. This can make it rather difficult to go to work, buy groceries, or do just about anything without your dog.

Excessive barking – Nervousness can manifest in strange ways. While it’s not uncommon to see a dog bark at a car, a mail person, or another dog on the street, nervous dogs often bark at nothing. Woofing or even scratching at the walls is a sure sign of nervousness and discomfort.

Hiding – While this is typically thought of as a feline behavior, some dogs seek out hiding spots when they’re dealing with emotional trouble. Whether they’re behind the bed, under the desk, or tucked behind some furniture, you can let your dog enjoy their hiding space for a while, but if it goes on too long, consider seeking veterinary support.

Once you’ve picked up your pup from the vet and tucked them into their bed, it may be beneficial to give your dog space to calm down after the surgery and adjust to any hormonal changes they may be experiencing. If they’re already prone to skittish or loner behavior, it may heighten during this time.

Be patient, give your pup plenty of TLC when they’re in the mood, and they’ll most likely return to their snuggly selves when they’re fully recovered. Maybe even treat them to our dog birthday cake recipe!

When should my dog be neutered?

All dogs are not physiologically the same. Different breeds and sizes of dogs have different optimal ages for castration. According to a recent study, veterinarians and pet owners should work together to discuss the optimal age of neutering, instead of following a blanket age recommendation. Every dog owner should consult with their veterinarian about the health impacts of castration for their individual dog.

Historically, veterinarians have recommended neutering dogs before puberty. This not only minimizes the risk of unplanned litters, but also may offer behavioral benefits. Puberty and adolescence are the time when animals transition from youth to sexual maturity. In most breeds and sizes of dog, this period spans from 6 months to 2 years of age. Hormone surges during puberty can and do influence the behavior of any individual. Ask the parent of any teenager! If you’re considering waiting until social or structural maturity before neutering, be sure to talk to your veterinarian in-depth about what to expect with respect to your dog’s needs for exercise, training, appropriate and safe confinement, and appropriate social environments.

Why is my dog more aggressive after being neutered?

Recently, a well-respected Sydney academic published his behavioural data on over 6000 castrated male dogs. It’s created headlines like”Neutering Causes Behavior Problems In Male Dogs”.

Can this be true? You’ve probably been told that desexing reduces behaviour problems, not causes them!

The reality is, there’s been a debate about this for some time and no-one can agree. But we need to get it right.

Personally, I think the study in question is flawed. It uses a voluntary online survey that was distributed to breeder groups. That’s unlikely to give a reliable snapshot of the dog population. It also doesn’t have a ‘control’ population of entire dogs.

But to be fair, no study is perfect. The answer is to not look at just one, but consider them all. To try to answer the question, that’s what I’ve done here.

Below is a summary of every study I can find that compares aggression towards people between entire and desexed dogs. If it looks a mess now, it’ll hopefully make sense once I explain it afterwards (yes, I read every paper).

Studies on single breeds are of limited use. Golden Retrievers are such placid dogs that their aggression is likely to be of a different nature. Aggression in Springers is suspected to be genetic in origin, especially in the show lines. I place little relevance on these papers, so bear with me while I remove them…

As aggression gets more serious, results are clearer. Of the remaining studies, let’s look only at the dogs being treated for aggression or reported for dog bite to people. Now it looks like this:

Whether you agree or not I hope you can see the reasoning. Random surveys of dogs are going to give different results to studies looking at acts of aggression. But I haven’t quite finished with the confusion.

A reason that entire males might be unfairly blamed is that poorer quality dog owners may also be less likely to desex their dogs. That means that some of the aggression might just be because the owner is an idiot and has raised the dog badly.

A reason that desexed males might be unfairly blamed is that when behaviour problems in males develop, most vets will recommend desexing. That will push more aggressive dogs into the ‘neutered’ groups as desexing after the event is unlikely to work. This is suspected to have happened in the Golden Retriever study.

Additionally, it is feasible that aggression at the vet could have started with a stressful or painful desexing experience, especially in past times when pain control was poor.

In conclusion, the ‘truth’ will probably be that desexing is good for some types of aggression but worse for others. I suspect it slightly increases the incidence of fear aggression (which often goes unreported) and reduces the more dangerous forms of human-directed aggression.

A clue to this is the dog bite statistics again. When we go one step further and look at fatal dog bites, the majority are children and they mostly involve undesexed males (Sacks).

One of my current concerns regards the delaying of desexing until over 12 months in large breeds. Let me be clear: I support it. However I have seen two lovely Rottweilers become dangerous during the waiting period, and they are likely to stay that way.

There’s no point worrying about a 5% risk of joint problems when you end up with a far worse problem. I advised the delay but I also believe these two dogs should have been desexed as soon as their behaviour started changing. Their futures are now bleak.

I don’t expect to sway anyone’s opinion, and I don’t even want to. All I want is to get the idea across that this debate is a lot more complicated than it looks. It’s full of people with vested interests on both sides only quoting the studies that agree with them.

*Significant meant the measured difference between the groups had a p-value of <0.05. It’s how we (somewhat arbitrarily) decide if a result is real or not. To learn more, read our guide to making sense of scientific research.

I can supply copies of the references (below) on request. If you know of any other studies that compare aggression in neutered and entire male dogs, please let me know!

Have something to add? Comments (if open) will appear within 24 hours. By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.

Borchelt, P. L. (1983). Aggressive behavior of dogs kept as companion animals: classification and influence of sex, reproductive status and breed. Applied Animal Ethology, 10(1), 45-61.

Casey, R. A., Loftus, B., Bolster, C., Richards, G. J., & Blackwell, E. J. (2014). Human directed aggression in domestic dogs (Canis familiaris): Occurrence in different contexts and risk factors. Applied Animal Behaviour Science, 152, 52-63.

Gershman, K. A., Sacks, J. J., & Wright, J. C. (1994). Which dogs bite? A case-control study of risk factors. Pediatrics, 93(6), 913-917.

Guy, N. C., Luescher, U. A., Dohoo, S. E., Spangler, E., Miller, J. B., Dohoo, I. R., & Bate, L. A. (2001). Demographic and aggressive characteristics of dogs in a general veterinary caseload. Applied Animal Behaviour Science, 74(1), 15-28.

Hsu, Y., & Sun, L. (2010). Factors associated with aggressive responses in pet dogs. Applied Animal Behaviour Science, 123(3-4), 108-123.

McGreevy, P. D., Wilson, B., Starling, M. J., & Serpell, J. A. (2018). Behavioural risks in male dogs with minimal lifetime exposure to gonadal hormones may complicate population-control benefits of desexing. PloS one, 13(5), e0196284.

Messam, L. L. M., Kass, P. H., Chomel, B. B., & Hart, L. A. (2008). The human–canine environment: a risk factor for non-play bites?. The Veterinary Journal, 177(2), 205-215.

Podberscek, A. L., & Serpell, J. A. (1996). The English Cocker Spaniel: preliminary findings on aggressive behaviour. Applied Animal Behaviour Science, 47(1), 75-89.

Podberscek, A. L., & Serpell, J. A. (1997). Environmental influences on the expression of aggressive behaviour in English Cocker Spaniels. Applied Animal Behaviour Science, 52(3-4), 215-227.

Sacks, J. J., Lockwood, R., Hornreicht, J., & Sattin, R. W. (1996). Fatal dog attacks, 1989-1994. Pediatrics, 97(6), 891-895.

Shuler, C. M., DeBess, E. E., Lapidus, J. A., & Hedberg, K. (2008). Canine and human factors related to dog bite injuries. Journal of the American Veterinary Medical Association, 232(4), 542-546.

Van den Berg, L., Schilder, M. B. H., De Vries, H., Leegwater, P. A. J., & Van Oost, B. A. (2006). Phenotyping of aggressive behavior in golden retriever dogs with a questionnaire. Behavior genetics, 36(6), 882-902.

Wright, J. C., & Nesselrote, M. S. (1987). Classification of behavior problems in dogs: distributions of age, breed, sex and reproductive status. Applied Animal Behaviour Science, 19(1-2), 169-178.