The “Quick Fix?”: Neutering As A Treatment For Aggression

Today’s topic is a juicy one with lots of real-life relevance, so I hope you’re excited!  If you’re a dog owner, or someone who works with dogs, how often have you heard some variation of the following:

“My girl has been growling at me over her food bowl lately!  She thinks she’s the queen of the house.  I really need to have her spayed and nip this in the bud.”

“Oh, your dog is barking and lunging at other dogs on walks?  And he’s intact?  Well, there’s your problem…”

“My dog bit a friend of mine who was visiting last night… it’s so upsetting.  My vet said we need to neuter him ASAP or this will keep happening.”

******

As a veterinarian, I can tell you that this line of reasoning is extremely common.  We frequently see clients who schedule their dogs to be spayed or neutered in an effort to resolve a wide variety of behavior issues – usually some type of aggression, but also anxiety issues, training problems, and general “stubbornness.”  Many of my behavior clients specifically ask about this as a potential treatment option, if their pet happens to be intact.

And really, it’s not hard to see where this idea comes from.  It almost feels like common sense, doesn’t it?  We tend to associate testosterone with more aggressive behavior, especially in males.  Less testosterone should equal more docile behavior… right?

The other major factor, unfortunately, is that a lot of dog behavior advice in the media and popular culture still has a tendency to pin most behavior issues on dominance, or conflicts over social status – so it makes a certain amount of sense to think that by spaying or neutering the dog and “taking them down a notch” in the pecking order, we might be able to fix the problem.

So what does the science say?  Is this a worthwhile recommendation that we should be making, or not?

The answer might surprise you.

The truth is, there is very little evidence to support the idea that spaying or neutering is an effective strategy for reducing aggression in dogs.   Most controlled scientific studies on this question (and there have been many!) show that whether a dog is spayed or neutered has no impact at all on the likelihood that they will be aggressive in any given circumstance.

As an example:

Earlier this year, a major study of more than 13,000 dogs ¹analyzed the effect of spay/neuter status and age that the procedure was performed on three different types of aggression – towards familiar people, strangers, and other dogs.  (This is a huge sample size, and the study was very detailed – I highly recommend reading the paper for yourself if this is something that interests you!)

By and large, no significant effects were found.

Interestingly, under one type of statistical analysis, the researchers actually found a modest increase in the risk of aggression (towards strangers, specifically – no change in the other categories) in male dogs neutered between the ages of 7-12 months.  The authors discuss some possible reasons for this finding and acknowledge that we don’t have enough information yet to know if this is a real effect vs. a statistical fluke of some kind, but it’s not the first study to show similar results.

Bit of a shocker, right?

It has been theorized that, if there is actually a true increase in the incidence of aggression in spayed/neutered vs. intact dogs, this could be due to the reproductive hormones having some kind of modulating effect on behavior.

But really, the jury is still out.  I don’t think we have enough evidence at this point to say whether or not spay/neuter status increases risk, although I’m very interested to see further studies on this topic in the future.

I AM comfortable, however, saying that spaying or neutering your aggressive dog is not likely to solve the problem.

And honestly, when you stop and consider what we know about aggression and its underlying causes in dogs, this shouldn’t surprise us at all.  The vast majority of aggressive behavior in pet dogs is related to anxiety, stress, or frustration – not social status.  Effective treatment for these issues is based on addressing the dog’s fear or discomfort through classical conditioning, and/or using reward-based training to teach a different behavioral response to the trigger.

Its gonads, for the most part, aren’t relevant.

Now, there are a few notable exceptions to this rule – namely intact males who consistently have trouble getting along with other males, and female dogs who only show aggressive behavior during their heat cycles.  In these cases, spaying or neutering can absolutely be helpful!  But for most dogs with more run-of-the-mill aggression issues (leash reactivity, resource guarding, biting visitors, etc.), it probably won’t make any difference.

Which begs the question: does all of this mean that you shouldn’t bother having your dog “fixed”?

No, not at all!  There may be many other valid reasons to consider altering your pet.  Even though it’s not likely to help with aggression, there are other behavior problems that do respond well to spaying or neutering in many cases – including urine marking, excessive mounting or “humping” behavior, and roaming.  Having your dog altered also prevents accidental matings, which one could argue is especially important in dogs with significant behavior issues, as these dogs should not be bred.

From a medical standpoint, spay/neuter is a thorny issue.  Potential advantages include prevention of mammary cancer and pyometra (a life-threatening uterine infection) in females, and prevention or reduced risk of testicular cancer, benign prostatic hypertrophy, and perineal hernias in males.  However, there is also growing evidence that altered dogs may be at an increased risk of developing orthopedic problems and certain types of cancer, especially if the procedure is done before they’re fully grown.

The take-home message?

My personal feeling is that the decision to spay or neuter your dog should be made on a case-by-case basis after discussion with your veterinarian.  There are valid pros and cons for every situation.  Just don’t expect it to fix your dog’s aggression issues.

Chances are, his testicles aren’t the problem.

1: Farhoody, Parvene et al. “Aggression toward Familiar People, Strangers, and Conspecifics in Gonadectomized and Intact Dogs.” Frontiers in Veterinary Science. (2018)

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related