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Without Warning: Unprovoked Aggression in Dogs

Yesterday while walking Rex, the little casanova spotted a cute little cream colored, female shaggy-type diva-dog and began whining to…

Unprovoked Rottweiler baring its teeth and barking.

Yesterday while walking Rex, the little casanova spotted a cute little cream colored, female shaggy-type diva-dog and began whining to rendezvous with her. We walked towards her and politely asked her Mom if she was friendly with other dogs. “Oh, yes…” her Mom replied, “She loves other dogs.” Diva-dog began rapidly wagging her tail and seemed excited to welcome Rex’s advance. They quietly sniffed noses for a minute when suddenly Diva-dog stiffened, turned into Devil-dog, and went on the attack! She raised her hackles and let-out a horrifying yapping growl, thrusting herself towards Rex, startling all of us… especially Rex!

unprovoked aggression in dogs

The first mistake was to assume that Diva-dog’s tail wagging was friendly and welcoming. A wagging tail is not necessarily a sign of friendliness….especially a “rapidly” wagging tail, as in Diva-dog’s case. You can read more online about deciphering tail wagging language, but most experts agree that you should be wary of a rapid or almost “vibrating” tail wag. Also, Diva-dog’s sudden excitement upon the approach of a strange dog may have been misinterpreted. Perhaps her excitement is better defined as nervousness… agitation maybe?

What would make a dog suddenly, without warning or provocation, react aggressively towards another dog?

A Bad Experience

Dogs don’t soon forget if they experience an unwarranted attack by another dog. Your once friendly, well-adjusted little pooch may have had a bad experience at a dog park, for example, and now he is constantly on the defense fearing that another dog will hurt him. Maybe Diva-Dog was afraid that Rex would attack so she did not want to appear weak or vulnerable.

Another key factor to consider here is the pack theory of dominance. Dominance theory suggests that dogs behave like wolves in a wild pack, competing for rank and resources. In a situation like this, Diva-dog might have seen Rex as a threat to her position in the pack or to her resources, like her owner. This can often trigger aggressive responses.


Diva-dog may be possessive over her owner and see other dogs as a threat. This possessive behavior would put her on high alert, even when there is no threat at all. A possessive dog consistently feels anxious and “stressed”. This could also be interpreted as jealousy, a common emotion in dogs. Dogs can get jealous when they perceive that their owners are giving attention to another dog, potentially triggering aggressive behaviors. Aggression is the way she protects herself.


It’s easy to confuse “Possessiveness” with the need to “protect”. If Diva-dog felt that her Mom was in danger, she may have been attempting to shield or guard her from a perceived adversary. A protective instinct can be so strong in some dogs that it may very well cause unprovoked aggression.

Redirected Frustration

While chit-chatting with Diva-dog’s Mom she mentioned that Diva-dog had unknowingly been inside all day with no way to relieve herself. This was her first potty-walk since early morning and it was around 5:00PM at the time! Could it be that Diva-dog was frustrated and unjustifiably
redirected her frustration towards Rex?

Brain Chemistry

On the other hand – don’t laugh – Diva-dog could honestly have, well… a screw loose. Brain chemistry quirks are not all that uncommon, especially in cases of irresponsible breeding. Unfortunately, dogs can suffer from chemical imbalance issues just like humans do.

Other reasons

Pain, fear, dominance, old age (not in this particular case), territorial issues, illness… There are a slew of possibilities as to why an otherwise friendly dog would suddenly exhibit aggression. However, the real cause for concern is whether or not the problem is on-going. If your friendly, well-socialized dog suddenly and continuously begins showing signs of aggression, you should not dismiss it. Start first with a medical check-up from your vet to eliminate any physical cause. With your veterinarian’s guidance, an animal behaviorist may be your next course of action.

It may take a while to repair Rex’s broken heart, not to mention his wounded ego, but he’ll recover soon enough. “There are plenty of other fish in the sea”, I keep telling him. He just tilts his head… he hasn’t a clue what I’m talking about.

Consider also that dogs, like many animals, have a survival mode when lost or feeling threatened. They can become more aggressive, especially when they perceive a threat to their safety. This could have been the case with Diva-dog’s unexpected reaction.

If Your Dog Attacks Another Dog: A Step-By-Step

A shepherd mix and black lab mix aggressively fighting at dog park.

Dog fights can be scary and unpredictable situations that can cause injuries to both the dogs and their owners. As a dog owner, it is important to take quick action to prevent further harm to your dog and others involved.

Here’s what to do if your dog attacks another dog unprovoked:

  1. Stay Calm: Dogs can sense our emotions. If you panic or become aggressive yourself, your pet may take that as a signal to escalate the situation further. instead, take a deep breath and try to remain as calm as possible.
  2. Avoid Physical Contact: It is best to avoid physically separating the dogs, especially if they are large or aggressive. Grabbing the dogs by their collars or attempting to physically pull them apart can result in serious injuries.
  3. Distract Your Dog: From a distance, clap your hands or shout loudly to try to startle the dogs and break their focus on each other. You could also use a spray bottle filled with water or vinegar, a squeaky toy, or a loud whistle to grab their attention.
  4. Create A Barrier: If possible, use an object such as a chair, broom, or trash can to create a physical barrier between the dogs. This will help to separate them and prevent further harm.
  5. Remove Your Dog: Once the dogs are separated, safely remove your dog from the area with a lead or slip lead and check for any injuries. It is important to seek medical attention for your dog if necessary.

If you discover that your dog is prone to attacking other dogs unprovoked, work to take precautions for next time. First, work with your vet to rule out any medical reasons for the sudden aggression. Next, work with an accredited dog trainer to help your dog become more calm in social situations. Until your pet has broken this habit, avoid unnecessary situations that could cause your dog to become aggressive.

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