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Dog Suddenly Aggressive Towards Other Dog In the House

What should you do if one dog is being aggressive towards the other dog in your own house?

Some dogs may even attack their fellow canines, leaving owners with lots of questions.

Wondering about how to reintroduce the dogs? Should you separate them?

What’s the line you should draw when it comes to the safety of other members in the house?

And most importantly why are your dogs even fighting and how can you stop it long-term?

While it’s always saddening us to witness our beloved dogs fight each other, the problems are often pretty easy to solve if owners commit to the training.

You’ll learn why one dog may have become aggressive towards the other and how you can stop it.

But you’ll also what the signs of a serious fight are and how you go about reintroducing and separating the dogs.

8 Reasons Why Your Dog Is Suddenly Aggressive Towards Other Dog

Reasons why your dog is suddenly aggressive towards the other dog include resource guarding, food aggression, redirected overexcitement, but also medical issues that cause pain.

If you recently introduced a puppy or rescue dog, that may be the reason.

Seniors are often suffering from medical issues ranging from hip issues to doggy dementia and that may cause a short fuse or disorientation.

External changes are also reasons why your dogs may not act like themselves.

Here’s a complete list of why dogs are suddenly aggressive:

  1. Resource guarding / food aggression
  2. Redirected overexcitement
  3. Lack of exercise
  4. Desire to be left alone
  5. Jealousy
  6. Medical issues
  7. Recently neutered
  8. Territorial issues / previous aggression
White brown dog lying on the floor.
Photo by Aleksey Boyko on Shutterstock

While your dog might not outright attack the second dog in your household, signs of aggression can be a tell that something might happen in the future.

How can your dog display aggression towards your other dog?

  • Growling or snarling upon approaching
  • Baring teeth when food or toys are around
  • Snapping your other dog when overexcited
  • Redirecting leash reactivity towards other dogs
  • Bullying the weaker (usually smaller or younger) dog

These signs can all be perceived as aggression and can be indicative of future problems that might arise.

A very tense relationship is never welcome and should be resolved immediately upon being noticed, but what can you do?

My Dog Keeps Attacking My Other Dog For No Reason

Dogs never attack another dog for no reason and there’s always an underlying behavioral issue or an undetected medical issue causing pain.

While it may seem like our dogs just go into a murderous frenzy out of nowhere, that’s actually almost never the case.

Dogs always communicate using their body language which includes facial and vocal gestures like growling, body postures, and tail positions.

We humans can sometimes have a hard time reading these signs but even though threats can be pretty clear to dogs, they too can challenge their fellow canine. And sometimes both refuse to back down.

In other cases, it’s just known issues that one dog has and the other doesn’t, as is the case with food aggression.

While the aggressive dog may have initially triggered a dog fight, your other dog might as well be the first to attack. Every dog has a different threshold for what they take.

Keep in mind that it’s never your dog’s fault, some dogs just have a tendency to take less bullying than others and they might strike the provoking dog.

As a responsible dog owner, it’s your responsibility to take precautions if one of your dogs has known issues like resource guarding, food aggression, not wanting to be annoyed by your new puppy, and so on.

How To Stop Dogs From Fighting In the Same Household

You can stop dogs from fighting in the same household by addressing the underlying behavioral issue such as food aggression and counter-conditioning a positive response.

When it comes to stopping your dogs from fighting at home (or outside), it’s important to note that I’m referring to constant nagging, snapping, growling, and so on – not any immediate threat or dog attack.

I have an article that covers the actual dog on dog attack if you’re interested.

To stop dogs from fighting, the most important question is why your dogs fight in the first place.

Once you know the root of the problem, you can take care of it.

1. Food Aggression / Resource Guarding

The basic explanations for fights with dogs are always resource guarding and food aggression.

Pitbull jealous of other dog.
Photo by Tara Lynn and Co on Shutterstock

If one dog is known to have either of these issues, please take care of it early on and read the linked articles.

2. Redirected Overexcitement

If you walk your dogs outside or guests are over and one of your dogs redirects the negative energy to your other dog due to his level of excitement, training will be required.

If that is the case, it’s best to walk your dogs separately and work on the overexcitement with lots of new situations, dogs, humans, noises, etc.

The whole desensitization and socialization package.

My Rottweiler puppy was quite overexcited too (which presented as tension on the leash, nothing serious) and the causes and ways to solve this are almost always identical which is why I’ve written an article on this too.

3. Lack of Exercise

If one of your dogs lacks exercise, this could be another reason why he is constantly nagging your other dog.

Besides extensive walks, there are several other things you can do to entertain your dog in your own backyard.

Make sure to adjust the amount and kind of exercise to your dog’s breed, age, and individual needs.

Sometimes this also means walking the dogs separately as they can have different exercise needs.

A tired dog is a good dog.

4. Annoyed Dog (Puppy Alarm)

When people introduce a new puppy into the family, the adult dog might not be so happy.

Some adult dogs despise puppies while others handle them very well and can be the best teachers

If your dog just doesn’t have the temperament to deal with puppies in their face all day, that’s okay.

If one of your dogs constantly annoys the other dog, you have to keep this from happening again and teach them how to respectfully treat and measuredly correct each other in an appropriate way.

5. Jealousy

When you introduce a new rescue and he’s all the rave, neighbors come over and pet him, he gets all the attention, then that may be great for him but much to your other dog’s dislike.

Dogs can feel some form of jealousy and it’s important to teach your first dog to handle jealousy but also make sure that both get attention equally.

Go on bonding trips together and make sure they connect each other with positive things and not with negative experiences.

6. Medical Issues

Medical issues can cause one of your dogs to suddenly start attacking the other dog in the household and a vet visit is required to rule that out.

Ruling out physical injuries can be tricky, but ruling out mental issues? Even harder.

You can check simple things like foreign objects stuck in the paw yourself.

Injuries are often not discovered right away and the resulting change in mood might be perceived as aggression if there’s another dog in the household.

Older dogs often suffer from canine dementia but dogs of all ages can suffer chemical imbalances, hormone issues, and so on.

7. Spay or Neuter

If your dog was recently spayed or neutered, then hormone balancing may be the cause of your dog’s aggression towards your other dog.

Read up about the risks of spaying and weigh them against the benefits to make sure you know all about possible behavior changes upfront.

8. Territorial Issues

I’ve decided not to include “dominance” since many people immediately connect that to the outdated dominance theory in dog training.

However, if you introduce a new dog, issues can happen if the introduction to each other was poor or non-existent.

Whether you believe in pack theory or not, it’s important that your dogs listen to you and recognize you as the leader and guide in which case training will be far easier.

Dog-on-dog aggression can not only happen between males but also between females or even male and female dogs.

If your new rescue has come with baggage in form of dog aggression, you can resolve the issues with the steps and articles outlined above that include socializing and desensitizing your dog to others in order to create a positive connection.

The assistance of a behaviorist may be necessary.

Reintroducing Dogs After a Fight

Reintroducing both your dogs in the same household is an important step on the road to rehabilitation.

In some cases, poor introductions to the new family addition are the cause of the other dog’s non-acceptance.

Some dog breeds defend their territory pretty harshly since that’s what they’re bred to do.

If you’ve just dropped a new dog into the other dog’s territory, the harmony is bound to be tested.

Make sure that any and all introductions to each other happen on neutral ground. Introductions shouldn’t start with head-on meetings either since this can make one of your dogs uncomfortable.

Start by having somebody else lead the new dog towards you and then just start walking with you and your dog in the front.

Next, you can start with the meeting where they sniff each other more extensively.

Some dogs do not have any issues with dogs inside their territory (like my female Rottweiler), it’s still good to take precautions to avoid any confusion.

How To Tell If a Dog Fight Is Serious

There are a lot of signs that a dog fight is serious such as an injury (i.e. one dog was bitten), tense body language, hackles, whale eye, and more.

If a serious fight develops, it’s time to quickly intervene.

After this happened or even when you’re just suspecting it, you should never leave your dogs alone if they’re not separated (and if that’s not possible, they should wear muzzles).

Muzzles are also mandatory if your dog is known to redirect any perceived aggression towards you, or other dogs and people.

I’d never recommend to anyone that they should let any dog fight “play out by itself”.

While there certainly is a threshold when a dog attack gets really serious, you don’t want to get to that point.

As discussed above, if you spot signs of aggression, intervene and separate the dogs until you have a clear plan of what to do now and how to resolve any issues that may have built up over a long time.

How To Discipline a Dog After Fighting

While dogs do learn with proper guidance, corrections, and counter-conditioning, there’s nothing that you can immediately do that will resolve the issue.

I actually have a full article on how to discipline dogs after fighting.

There’s also an article on how to discipline your dog in general.

Keep in mind that any correction should always be clear, but measured to not achieve the reverse effect of your dog losing respect for you too.

Separating the dogs is not a long-term solution, although it will work in the short term until you’ve figured out what the problem exactly is and how you can resolve the issue.

On the contrary, constant separation will put much stress on both dogs as well as yourself and other family members in which case a harmonic life isn’t possible anymore.

If you go so far as to isolate one of the dogs, it might cause even more issues and resentment expressed as aggression than before.

My Dog Killed My Other Dog What Should I Do?

This is a question you’ll find on Reddit more often than you’d probably like to.

It’s a sad story, no matter what the circumstances were but it’s important to not stick your head in the sand and start addressing this issue.

The advice that’s spread by people that presumably never really read up about dog training and behavior can be really dangerous.

Next is the popular “just surrender that dog to a shelter” or even better “euthanize the dog”.

Nearly no shelter will take a dog that killed another animal, much less another dog.

Even if they did, they probably couldn’t train it and the dog would end up in the hands of a layman, without the slightest mention or explanation of the incident.

Euthanizing a dog for a mistake the owner made is also completely unacceptable in my personal opinion.

No matter how you look at this, falsely assessing your dog(s) and/or not taking security precautions is a mistake.

We can’t fix the past, but we can act differently in the future.

Start training with professional help.

And I don’t just mean a certified trainer, I mean a really qualified behaviorist that has a proven track record and that you trust.

Be ready to put in lots of time, effort, and money.

If this is no option for you, it’s completely understandable.

Sometimes, circumstances in life make it hard to deal with these kinds of situations but you should at the very least try to solve the issue yourself (with professional help if needed).

In case you want to surrender the dog to a shelter or another owner directly, do your research, explain everything in detail, and do not downplay anything.

A dog that has taken a life can definitely be very dangerous and should only go out muzzled and not interact with other dogs unsupervised.

To summarize this, dog on dog aggression inside your own home can be really sad to watch and if you feel helpless, remember that there is a way out to teach your beloved canines to accept each other.

Lots of problems are easy fixes with the right training and patience and if you have any questions along the way, feel free to ask them in the comments!

Disclaimer: This blog post does not substitute veterinary attention and does not intend to do so. I am not a veterinarian or pet nutritionist. If your dog shows any sign of illness, call your vet.

About Danielle

I am the founder of PawLeaks where I share weekly tips on dog training and behavior. Sharing a passion for dogs and helping owners to solve problems through understanding canine behavior and modification is my number one goal.

Cassie

Saturday 31st of December 2022

Hello. I have a question. I have two dogs that have been buddies for a while. A 3 year old lab, and a 1 year old mix.

Yesterday, my mixed pup was hit by a car and was in the hospital overnight. He is better, but still has a long road ahead of him.

Since I brought him home, my black lab is suddenly growling at him and putting his hackles up around him.

When the pup was hit by the car, his breathing almost sounded like snarling, and I’m thinking maybe the lab took it as a threat?

I don’t know what to do about this. They were best friends, and now my lab seems to hate the pup.

Any advice?

Danielle

Saturday 31st of December 2022

Hi Cassie, sorry this happened to your pup, hope he'll get better soon. The fact that the change is so sudden probably means that it has to do with the accident. Miscommunication is possible and your Lab might be confused or just sense the general pain in your pup. Regarding the snarling: It usually settles if your Lab is well socialized and recognizes the body language etc.

If you're worried, please don't hesitate to consult a certified behaviorist in your area, looking at it in person would be much more helpful.

Hope that helps, Danielle

Saundra

Friday 18th of November 2022

Hi Danielle, A little over a month ago we spotted 3 mausers and realized they were living in the bushes of the apartment adjacent to ours. We were told my many of our neighbors that they had been seen running around the area for somewhere between 3-4 weeks. No one had had any luck getting close to any of the dogs but they would leave food out for them so the dogs would make their way around the neighborhood eating what was left for them. After a few days we were finally able to get all 3 dogs, 2 at first and the 3rd the following evening. Of course all of them were scared and timid when we first got them, but they quickly warmed up to us and they are very comfortable, loving, and trusting. All 3 look somewhat different with completely different personalities. We haven't been able to find out much about their past and how they ended up on the streets or exactly how long they had been on their own. They are very protective of each other and when outside they get along extremely well. They are all female. We think that they all differ in age, one seems to be much older than the others. As I mentioned earlier we were able to get 2 of them on the same night. The older one, Tang, and the one we think is in her teens, Wu. ( The baby we named Clan) Anyways, Wu and Tang seem to get along, however Tang refuses to play with Wu the way she plays with Clan. And you can easily see how sad it makes Wu when she is rejected by Tang and when she see her playing with Clan. It's heartbreaking. The bigger problem, that seemed to start once all 3 had adjusted and became comfortable in our home, is that Tang will snap, growl and show her teeth when Wu approaches her, most of the time when Tang is resting, but she doesn't do that when Clan approaches her. When she snaps and growls at Wu, Wu will start whimpering, wagging her tail and lowering the front portion of her body. This will continue until one of us tell them to stop. Again Wu looks so sad and heartbroken when Tang does this to her and it happens very often. Also, the growling and snapping has gotten worse over time. During walks they get along extremely well. They often walk together cheek to cheek as if they are attached. We do take all of them one walks together and try to take them out individually once or twice a week. Tang will put on a show when it's feeding time and she will come up to us when she wants love and attention, and aside from playing with Clan every now and then she likes to be left alone, but will remain in the same room as us. I don't know if it matters but Wu is a bit bigger than Tang and Clan. We can't figure out why she snaps at Wu and why Wu whimpers and bows down to her or even why Wu keeps going back to her again and again. And although in general they seem to get along the only time Tang will not act this way towards her is while they are eating and are getting ready to go out on their walks or while they are out on their walks. Again it's extremely sad to see Wu so heartbroken every time she is rejected by Tang. What can we do to stop this from happening?

I appreciate any insight and advice you can offer.

Carissa

Saturday 29th of October 2022

Hi I have an 11mth old female frenchie along with a 7 year old frenchie and the same age 2 poodles they have all gotten along until 2 days ago where there was a fight and the two frenchie attacked the Female poodle I did not see the fight , my daughter heard it and went and separated them , the poodle had no actually physical signs of the attack but now the 11mth old stalks her as soon as I let them out together she runs straight to her and follows her standing over her , her hair on her spine is standing upright so I know she’s looking to attack and I think she’s just realised that she’s now more dominant but she’s a lot bigger than the poodle and I’m worried that she could potentially kill her , what can should I do to make sure this doesn’t occur ?

Danielle

Monday 31st of October 2022

Hi Carissa, so there's a lot going on with 4 different dogs and the dynamics play a role too (when was who added, any recent medical issues, spay, adolescence, resources etc.). I'd really suggest you consult a professional behaviorist, especially if you notice signs such as stalking, hackles, and so on. The dynamics can certainly change as the dog gets older and I actually have an article if your pup bullies the older one or vice versa.

A professional could look at it and determine the issue which is practically impossible without seeing the dogs in person.

Cheers, Danielle

Michelle

Saturday 3rd of September 2022

Hi Danielle, I have two dogs, both are same crosses, westie X bichon One is male Buddy almost 11 the other a female Mia 9.5. They are both infertile now. Both are extremely loving, Buddy is very laid back and docile and loves everyone. Mia is connected to me with a piece of elastic, all had been wonderful but for the past 12 - 18 months Mia attacks Buddy for zero meaning ! They can be sleeping deeply, she will wake up and it’s like she zones out and prowls towards Buddy, it happens at least once a day, mostly if my husband is in the same room as us, on their own they are fine ( as far as I know but they aren’t left alone very often) I have wondered if either one were in pain or if . Mia was suffering with dementia? She attacks him when my grandchildren are here, as if she’s protecting them as Buddy likes to bark lol and the kiddies don’t like it. But to do it for no apparent reason, her body goes stiff it’s so hard to explain. Buddy is a little bit of a drama queen I even thought he may let out a sense of fear ? I literally hold her back with my forearm until I can get her to look at me, and it takes a while for her to come back it looks as though her eyes are are bewildered …. Any advice would be great please

Many Thanks

Danielle

Sunday 4th of September 2022

Hi Michelle, due to both dogs being seniors, I'd definitely consider medical issues or some form of dementia. A vet visit might be good, followed by booking a session with a trainer. It's really unusual if they've been living together for a long time and while protecting the kids might be a reason, getting up and immediately attacking might indicate a medical issue (unless, of course, the body language says otherwise).

Deb

Thursday 28th of July 2022

We have 2 female dogs. An 11 yr old small poodle/Schnauzer mix and a 3 yr old large lab/hound mix. We’ve had both of them since they were puppies. The 11 yr old has always been top dog and they have both gotten along happily without incident. The other night we had lots of family over and had a campfire. My daughter was holding the 11 yr old on her lap and put her down, the other dog was close by. The 11 yr old dog growled first, but then the 3 yr old dog grabbed the 11 yr old by the neck and started shaking. It was awful and unprecedented. We managed to get them separated and believe the older dog will be okay.

Never in my wildest dreams did I see this coming. We’re separating them when we aren’t right there and can deal with the 2 of them. But, I am worried what the 3 yr might do next. She has always been a barker and slow to warm up to people, but we believed she didn’t have a mean bone in her body or the capacity to hurt anyone. Now I’m not so sure. Any advice?

Danielle

Saturday 30th of July 2022

Hi Deb, there was probably something happening which caused the older dog to growl and the younger one to attack. Perhaps the older dog already noticed the impending attack or she wanted the younger one to just back off. It's hard to tell without seeing their body language, it might be best to consult a trainer especially since your dog is senior and attacks like this can be quite harmful.

It's good to keep them separate for now, but long term, I'd consult a qualified trainer to at least look at this and make sure it won't happen again.