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Why Is My Dog Suddenly Aggressive To Our Other Dog?

Why Is My Dog Suddenly Aggressive To Our Other Dog

You have two dogs. And they get along fine.

They have no problem spending time together, it’s even enjoyable for them.

And then, all of a sudden, one of your dogs shows aggression towards the other one. It’s weird, unexpected and potentially dangerous…

So, you start asking yourself what could be making one of your dogs act this way…

Not to worry – here you’ll discover:

  • 7 reasons why your dog acts this way.
  • What ‘resource guarding’ means and why it can trigger aggression.
  • Fact: Your dog could be in pain and you might not even know it (this can be a reason why it acts aggressive suddenly).
  • And much, much more…

Why is my dog suddenly aggressive to our other dog?

Your dog is suddenly aggressive to your other dog due to pain and diseases. They exhibit aggression by snarling, growling, and snapping at other dogs. Other causes of aggression include fear, resource guarding, being territorial, and sexual and maternal behaviors.

7 reasons why your dog is suddenly aggressive to your other dog

#1: Fear aggression

Dogs become aggressive for the following reasons:

  • They are in danger.
  • They cannot escape.
  • They want to defend themselves.

This happens if, for example, your dog is smaller than your other dogs. He might feel at a disadvantage and might react by being aggressive against other dogs.

Another scenario is when your dog came from a shelter. Without you knowing the full history, your dog could have been abused or neglected. 

In addition, they might have experienced a traumatic event. All these made the dog fearful or aggressive.

#2: Pain-related aggression

Pain Related Dog Aggression

Pain can bring out the worst in a dog.

They can become suddenly aggressive to your other dogs because of it. That’s because pain and discomfort stress them out.

So even the most insignificant thing, such as another dog passing by them, causes them to snarl or growl.

Pain can come from injuries or illnesses such as:

  • Cuts.
  • Arthritis.
  • Wounds.
  • Lacerations.
  • Bone fractures.
  • Internal injuries.

An ear infection can also make them aggressive. Especially if there are loud noises.

In addition, dental pain may cause these sudden changes in your dog. It could be a broken tooth or something lodged in the teeth.

#3: Resource guarding

Even the kindest dog will turn aggressive if another dog tries to take their possessions.

They are possessive of their food, chew bones, bed, and even their favorite human.

It is called resource guarding.

This research defined resource guarding as:

‘The use of avoidance, threatening, or aggressive behaviors by a dog to retain control of food or non-food items in the presence of a person or other animal.’

So if another dog gets too close to your dog’s favorite chew bone, your dog will show aggression by:

  • Snarling.
  • Growling.
  • Snapping.

How aggressive your dog becomes depends on the dog and the object. 

Look at it this way.

Your dog doesn’t mind letting other dogs sleep on his bed. But he would show aggression when other dogs try to take his chew bone.

This means that a dog puts value to his possessions. The higher the value, the more aggressive he becomes when others try to take it.

Resource guarding is a natural behavior in dogs. In fact, even humans do it. Why else would banks keep money and valuables in a vault? 

#4: Territorial aggression

Territorial Dog

Territory can also be a cause of aggression between your dogs.

Sometimes a dog ‘claims’ a part of the house against other dogs in the family. The couch, for instance. 

Perhaps the dog has established his claim on the couch. He is always the one on your lap or beside you on the couch. 

He then shows aggression when other dogs try to join you. The other dogs respond by backing off. 

And so from that moment on, no other dog has ever been on the couch.

#5: Disease-related aggression

Is your dog never the aggressive type? 

Then there could be an underlying reason behind their sudden aggression.

This can be caused by infectious or non-infectious diseases. 

In particular, tumors, trauma, and thyroid issues affect some parts of the brain. These can lead to aggression.

Cognitive dysfunction and brain tumors also signal the onset of aggression.

These are likely to occur in older dogs. But these can also affect dogs of any age. 

Speaking of senior dogs. They are prone to several age-related diseases such as dementia. This can also make them suddenly aggressive.

But if your dog shows weight gain, lethargy, and hair loss, it could be hypothyroidism. 

The VCA Hospitals define hypothyroidism as an underactive thyroid glands. It causes metabolism to slow down.

Other signs of hypothyroidism that you need to look out for are:

  • Getting cold easily.
  • Balding or thinning of hair coat.
  • Frequent ear and skin infections.
  • Having dry hair that sheds excessively.
  • More pronounced dark pigmentation of the skin.
  • Hair re-grows too slow or not at all after clipping.

If your dog experiences convulsions or sudden mood changes, it could be seizures. The aggression is brought about by momentary disorientation. 

#6: Sexual aggression

You know what happens when humans reach puberty. There are a lot of changes, particularly in the behavior.

It’s the same in dogs when they reach sexual maturity. And that is anytime between 6 to 18 months. 

Females usually reach this stage earlier than males.

One of the behavioral changes that take place is sexual aggression. This is usually brought about by mating behavior.

In particular, aggression occurs when a male dog competes for a female. Or when a female wants access to a male. 

This study observes that the mating success of males depends on several factors. One of which is ‘competing for access to partners.’ 

This could mean resorting to aggressive behavior against other male dogs.

The same is true in females. They could turn aggressive toward other dogs if they want access to a male.

#7: Maternal aggression

Do you have a dam that recently gave birth to puppies?

Have you noticed instances when they become aggressive? Perhaps when you try to come closer?

Not all dams exhibit maternal aggression, though. In fact, some dams allow their owners to help them during the birthing process.

But for dams that turn aggressive, this is usually temporary. Maternal aggression stems from abnormal maternal behavior.

When she shows aggression, it’s directed to the following:

  • Toward the puppies.
  • Any person or dog that approaches the nest.
  • Toward objects that a dam thinks are her puppies during a false pregnancy.

If you will check this video, the Doberman dam directs her aggression toward the sire:

Hormonal changes and pain also make a dam aggressive. They can attack or bite other dogs and even owners.

Sometimes aggression occurs in immature and anxious dams. 

Eventually, aggression decreases. It’s because the puppies grow and become less dependent on her.

3 tips to stop sudden aggressive behavior

#1: Check with the vet

Taking your dog to the vet should be your first choice. 

Especially if the aggression is brought about by pain or underlying medical conditions.

Your vet is the authority when it comes to prescribing treatments for whatever ails your dog. 

Thus, it is vital that you do not give your dog antibiotics or any other medicine for that matter. 

Because it might worsen your dog’s condition.

Note: Talk to the vet first before addressing the aggression as a behavior problem.

So before going to the vet, list all of the symptoms that your dog exhibited. It will help the vet rule out certain illnesses or diseases.

#2: Seek professional help

If you’re a first-time dog owner or you’re having trouble with your current dog:

Don’t be scared to seek the help of an animal behaviorist. Especially if aggression is caused by things other than pain and diseases.

Sometimes you can only do so much for your dog. That’s why it’s better to put the problem in the hands of a professional.

#3: Act on the aggression before it gets worse

Whoever says ‘Prevention is better than cure’ is telling the truth.

In applying to your dog’s aggressiveness, curb the problem as soon as you see the symptoms. 

For instance, in territorial aggression. You can take your dog away from the couch and to another room. 

Say, have them sit in the den. Then give them a reward such as a treat.

This helps to decrease the dog’s aggression toward other dogs that want to use the couch.