Why Would a Loving Dog Suddenly Become Aggressive? - Simply For Dogs
Dog Aggression

Why Would a Loving Dog Suddenly Become Aggressive?


You’ve probably heard stories that go something like “I don’t understand it; my dog was just sitting quietly on the sofa between me and my girlfriend, and all of a sudden, he turned around and latched onto her.” Or you hear, “He was playing with the kids, and everything seemed to be going fine, and then suddenly he snapped at Kayla.” Another common tale is “I was just petting him, and he grabbed my hand, and I ended up needing stitches.”

Usually, these stories end with “So I took him to the vet and had him put to sleep; after all, I can’t take that kind of chance again.”

That’s sad, because loving dogs don’t just suddenly become aggressive – there’s always a reason, even if we don’t know what that reason might be.

Even the Most Loving Dogs Can Show Aggression

I recently had a phone call from a woman who had adopted a puppy out of the first litter from Janice and Leroy. She was in tears because the dog (now three years old) had snapped at a neighbor’s child who was visiting her home, and now the neighbor was demanding that she have the dog euthanized. “There was no reason!” she said. “This kid has been here a million times; she loves the dog and the dog loves her! I don’t know what to do.”

With a bit of questioning, I learned that the dog had been soundly asleep, and the child had approached from behind to pet the dog. The dog woke suddenly, and not being able to see immediately who had initiated the contact, turned around and delivered an “air snap.” The child was terrified and ran home crying, and then the neighbor marched over with the sobbing child in tow. Voices were raised, nothing was resolved, and then I got the phone call.

Dog Aggression

I suggested that since the owner had been able to determine what had set the dog off, she might want to go over, apologize to the neighbor, explain, and try to make things right before matters got even worse.

The Outcome

When the owner went to the neighbor’s house, the neighbor still wasn’t in a good frame of mind, and reiterated that she wanted the dog put to sleep. The dog’s defense came from a surprising source – the child, who had been listening to the conversation. She immediately resumed sobbing, bordering on hysterical, and saying “Mommy, Gino didn’t mean to do it, you can’t mean for him to die, and if you do, then you’re just the most horrible, hateful, meanest mommy in the whole world!”

The dog’s owner seized the advantage, saying softly, “If I put Gino down, who’s she going to blame?”

Finally, cooler heads prevailed. The neighbor relented, and the child now knows not to approach Gino from behind when he’s sleeping.

The Moral of the Story

This long digression is simply by way of pointing out, again, the fact that a loving dog does not generally “turn.”

That’s not to say, though, that aggression in dogs should be taken lightly, and there can be other reasons why a normally loving dog might display aggressive behavior.

As I’ve said, there’s always a reason. Knowing the reason is the first step toward addressing the aggression, which is most of the time, simply the first indication of an underlying problem. Sometimes, it’s a “one-off” like the scenario I’ve described above, but more often, something else is at work, and if the aggression is not dealt with, it will usually escalate.

Most Dogs Don’t Want to Be Aggressive

A loving dog will almost always, if given the choice of aggression or another response, choose the other. Dogs want to have their needs met, and if they can have them met without resorting to aggression, that’s the course of action they’ll pick. Just knowing this makes it a lot easier to deal with aggression.

That said, though, I want to reiterated that aggression is serious, and you should never put off dealing with it. Most dog owners are not usually well-equipped to solve this sort of problem on their own, so it’s generally best to consult a dog trainer or an animal behaviorist. Don’t waste time, either – do it right away. The longer you live with the problem of aggression, the more difficult it’s going to be to correct. I can tell you too, that the dog trainers I know want to see you right after the first incident, and they just hate it when people come to them saying “He’s bitten three people.”

An “air snap” is a warning, and not necessarily a huge cause for concern – it’s usually the result of some action on the part of a human, however innocent. A bite is not a warning, and should never be ignored.

What Is Aggression?

Aggression in dogs is the same that it is in humans – a deliberate attempt to injure someone, or to intimidate someone by threatening to cause an injury. But when you’re considering what aggression is, you also have to think about what it isn’t.

As an example, some dogs “smile” differently than others. We usually think of a dog smile as the lips being pulled back, and the teeth visible but not bared. Some breeds, though (the Australian Shepherd is one example) tend to pull their lips back so that their gums are visible, and the teeth can look pretty scary. To know whether a dog is being aggressive, or simply smiling, you need to look at the rest of the body language. More on that in a bit.

Growling is another thing that doesn’t necessarily mean aggression. Many dogs growl when they’re playing, and some dogs even growl when they’re feeling particularly happy. Rottweilers are known for this – they might growl when having their tummies rubbed, for instance, as a way of saying “That feels good; do it some more!” Some breeds are simply more “talkative” than others.

Of course, that said, it’s worth keeping in mind that growling can be the precursor to full-on aggression. When that happens, the dog is telling you, “I would prefer not to bite you, but I will if I absolutely have to.” Another thing that you should keep in mind is that a dog who is about to bite might not necessarily growl beforehand.

So, how do you identify aggression? Take a look at the dog’s body language. Is he standing stiffly, staring at you, throwing his weight forward and raising his hackles? These are all signs that you could be in trouble. Most of the time you won’t see these behaviors from your own dog, toward you. These are the things you need to worry about when encountering strange dogs. If you’re concerned about aggressive behavior on the part of your own, ordinarily loving dog, though, there are things to watch for.

Signs That You Have Aggression Issues with Your Dog

If you’re reading this article, I’m thinking that you may already be concerned that your beloved pet might be a threat to you at some point. Here are some warning signs:

  • You’re afraid to take things away from your dog
  • You’re unable to approach your dog when he’s eating
  • Your dog growls at you when you try to put him off the furniture
  • You’re afraid of your dog for any other reason

To take this further, if you’re afraid to take your dog for walks because you worry that he might bite someone or try to fight with another dog, or if you’re constantly telling people to keep their distance because you’re afraid they might end up being bitten, then you have aggression issues with your dog. They’re not directed at you, but if they’re not corrected, the outcome could be very bad indeed. If your dog bites someone, or harms another dog, you could end up being sued, and your dog could end up being put down.

Reasons for Aggression

Dogs can have any number of reasons for displaying aggression. Here are some of the most common causes of aggression in normally loving dogs.

1. Mental Illness

If your typically loving dog suddenly displays aggression, your first course of action should be to see your veterinarian. The first thing you need to do is rule out mental illness.

We now know that in humans, clinical depression and bipolar disorder, to name just a couple of conditions that affect the brain, are not due to lack of character or a failure to “pull up our socks” – they’re the result of a chemical imbalance in the brain. In other words, it’s a physical problem that affects mental function, and requires medication to correct the imbalance.

Your vet can do bloodwork and other tests to determine if your dog’s brain is functioning the way it should, and can prescribe medication to correct the imbalance that’s causing the aggression.

2. Thyroid Dysfunction

If the thyroid gland is not producing the right amount of thyroid hormone, this is another condition that can cause aggression.

3. Lyme Disease

This is another disorder that can affect both humans and dogs, and in both species, can result in sudden aggression. Lyme disease is spread by ticks, so if your ordinarily loving dog has suddenly become aggressive, and you live in an area where ticks are known to be present, suggest that your vet have your dog tested for Lyme disease.

4. Rabies

Remember Cujo, the sweet-natured Saint Bernard in the Stephen King book (and later the movie) of the same name? He ended up being transformed into a slavering, homicidal hell-hound when he contracted rabies.

Thanks to increased public knowledge about the importance of regular rabies vaccines, the disease is fairly uncommon in dogs today. If your dog has not been vaccinated, though, this could be a cause of his sudden aggression.

I can’t stress enough the importance of vaccinating. There could be several reasons for sudden aggression in your typically loving dog, but if you keep the vaccinations up to date, you can definitely rule out rabies as a potential cause.

5. Brain Injury

A blow to the head can also be a cause of canine aggression, as can anything else that causes pressure on certain areas of the brain – tumors, or water on the brain, for instance.

6. Reaction to Pain

If a dog is injured, and you’re trying to help him, he might lash out at you thinking that you’re the cause of the pain. Think of it this way – if you’ve sustained an injury, and someone reaches for the affected area, your reaction is likely going to be to try to push them away. Your dog is going to have the same sort of reflex.

This actually shouldn’t be considered as “sudden aggression” – it’s more like “situational aggression.” However, I’m including it here simply because it seems like a good opportunity to warn you against handling an injured dog without first muzzling him. Even the most loving dog in the world can bite if he’s in pain.

7. Fear

A frightened dog can also be prone to sudden aggression, or “fear biting.” If you’re dealing with a strange dog, then you don’t know how loving that dog might ordinarily be, and the best course of action is to keep your distance. If it’s your own dog, avoid putting him in situations where he feels threatened.

8. Predatory Instinct

All dogs are predators. It’s simply in their nature. A dog that kills the neighbor’s kitten, for instance, isn’t evil, or murderous, he’s simply dog-like.

Predatory instinct becomes a problem when you don’t control your dog, and when you can’t handle his aggression. This isn’t a situation where a normally loving dog loses it – it’s perfectly normal. Undesirable, but normal.

Predatory instinct can be controlled to some extent with vigorous training, and often channeled through finding the dog a job, like agility training. It’s not “sudden aggression,” though – it’s hard-wired.

9. Territoriality

Having just said that dogs are natural predators, in the wild, they don’t survive mainly by predation. Mostly, they scavenge, looking for places where food is likely to be found. This is their territory, and they will protect it against other dogs.

In domestic dogs, this translates into guarding the food dish, and it’s why loving dogs will often react badly if you approach them while they’re eating. If you’re going to combat territorial aggression, or food guarding, you want to start when the dog is just a puppy. Make him wait for his food, put your hand in his food bowl while he’s eating, practice taking the bowl away, and so on. Do this before he’s big enough to fight you on the issue, and he’ll become very accepting of your occupation of his “territory.”

I’ve always done this early on with my dogs, and I’ve done the same with toys, offering them and then taking them away before the dog is big enough to think he can engage me in battle over something he wants. Because I do this, I’ve never had to worry about a loving dog suddenly showing aggression over food or property. In fact, people are often amazed that I can reach into my dogs’ mouths, say “Give me that,” and have the dog immediately hand over the object or the food.

A dog that snaps over food or toys is not displaying “sudden aggression.” He’s trying to protect what he feels is his, and it’s up to you whether or not you want to allow that. I would submit, though, that if your dog is around other people, it would probably be a good idea to train him to the point where food and property are not issues. A territorial dog isn’t necessarily an unloving dog, but the result (a bite) is the same regardless of the emotional state or basic good nature of the dog.

10. Protectiveness

Protectiveness is not a bad thing in a dog, but if not properly channeled, it can be a problem. For instance, many breeds of dogs are very protective of their families, to the point where they can be dangerous.

In the introduction to this post, I offered a scenario where a dog was playing with children, and suddenly bit Kayla. This is the sort of situation where a dog differentiates between “my kids” and “visiting kids.” A dog that is perfectly fine with his own family might perceive that “not his kids” are abusing “his kids,” and react in a way that, to the dog, seems perfectly normal. Again, this isn’t “sudden aggression” on the part of a normally loving dog – it’s an example of a dog being very protective.

This seems like a good opportunity to point out, as I frequently do, that you should never leave children and dogs unattended.

Protective aggression can also manifest in other ways – for instance, if your dog won’t let your boyfriend or girlfriend near you, he’s displaying protective aggression. Again, it’s not “sudden aggression,” so you don’t have to rush off to a trainer or animal behaviorist – you just have to work through the problem. See What to Do When Your Dog Hates Your Significant Other for more insight into this problem.

11. Frustration

If a dog becomes frustrated, and can’t take it out on whatever it is that’s frustrating him (that annoying German Shepherd next door, or letter carrier, or the UPS guy, or whatever), sometimes, that normally loving dog will take out his frustration on his owner. In this case, you might not be able to do much about the source of the frustration. After all, the German Shepherd’s people aren’t going to move away just because your dog is troubled by the presence of their dog. You still have to have your mail and your packages delivered.

With this kind of situation, you might need professional assistance. If the aggression is being turned your way, this is not sudden aggression on the part of a normally loving dog – it’s a serious issue, and you could end up being hurt. Don’t try to handle this on your own – see a pro.

12. Dominance

With dominance aggression, your dog wants to be the alpha. He might see you as weak and think that he’d be a better “pack leader,” and he might display hostility when you try to control him. Again, this is probably a job for a pro.

13. Maternal Issues

I’ve had three litters out of Janice and Leroy, and I’ve never once experienced a situation that’s fairly common – where the mother is so protective of the litter that she won’t allow anyone near the puppies, not even her human.

On the contrary, Janice is quite happy to allow perfect strangers to pick up her puppies and handle them. Janice’s perspective is that everybody is a friend, and it would never occur to her that anyone might want to harm her babies.

Not all dogs are like Janice, though. Sometimes, a perfectly loving dog can turn into a holy terror if she thinks she has to protect her little ones.

The best advice I can offer here is, if your ordinarily loving dog doesn’t want you near her puppies, respect her wishes. And once the litter is weaned, have her spayed, because often maternal aggression can be translated into generalized aggression once the litter is gone.

14. Play

I touched on this briefly before. Often, when dogs are playing, they become very vocal, barky and growly. This is perfectly normal, and if you’ve ever seen a real fight between dogs, you’ll immediately know the difference between “play aggression” and “real aggression.”

Again, though, this differs from “sudden aggression,” where a dog suddenly seems to “go off.”

Some people will suggest that you should curtail play aggression, on the theory that it will lead to “real aggression,” but that’s very unlikely to happen. In fact, play aggression actually helps dogs to learn when to pull back – a dog that is accidentally hurt during play will yelp, and the other dog will usually pull back. Your dog is far less likely to be aggressive if you allow him to play with other dogs.

So, we have lots of examples of aggression here. But “sudden aggression”? No.

The Final Word

Sudden aggression in loving dogs hardly ever happens. Usually, there’s a reason for aggression, and it’s not a matter of a dog “turning.” Rather, it’s a matter of humans making mistakes, or misinterpreting ordinary aggression as “sudden.”

If aggression is a problem in your dog, though, it really doesn’t much matter if it’s “sudden” or otherwise. It has to be dealt with, and if you can’t handle it on your own, you need the assistance of a professional trainer or animal behaviorist.

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