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Identifying Your Dog’s Triggers

Having a dog display aggression in any situation can be stressful. No one wants to have the "scary dog". It’s especially upsetting when you can’t pinpoint exactly what went wrong, because you worry that it could happen again. Dogs can’t explain what they’re thinking, so we have to pay close attention to the situation and their body language to figure it out.

First, let’s go over what an aggressive reaction looks like.

Aggressive Body Language in Dogs

Aggression can show itself in any of the following ways:

  • Lunging

  • Snarling and showing teeth

  • Sustained low-pitch barking

  • Snapping

  • Standing very rigidly, with an arched back

When a dog is in flight-or-fight mode, their choice usually depends on how confident they are. Timid, fearful dogs will run away if they can, but if they can become aggressive if they feel backed into a corner (literally or figuratively).


So what are some things that may be triggering your dog’s aggression? Here are a few examples:

  • Being touched is a common trigger, especially being picked up, having the ears cleaned, or having the teeth examined.

  • Dogs who haven’t been socialized around young children can be triggered by the fast, unpredictable movements of toddlers.

  • Unusual objects in the environment, such as balloons or Halloween decorations, can frighten some dogs.

  • Many dogs are upset by sudden loud noises, such as fireworks, thunder, and gunshots.

In these cases, it should be obvious what your dog is reacting to. If you tied balloons to your mailbox for your child’s birthday party and your dog is barking like crazy in that direction, you’re not going to think she suddenly developed a fear of mailboxes.

But some triggers are subtle or easily confused with something else, and you may have to do some detective work to figure them out.


Strangers can trigger dogs’ fear or aggression, especially if there is something unusual about the way the strangers look or move. Examples include very tall people, people wearing big hats, and people using canes or wheelchairs.

But if your dog is snarling at a tall man wearing a hat, it may be unclear what exactly your dog is reacting to: Tall people? Men? Hats? Or is it “none of the above,” and the man just made a gesture that your dog took to be threatening? You might not be able to tell until your dog meets another hat-wearer or another tall person, and you can start to put the puzzle together.

Leash reactivity can also be misinterpreted. If it seems like your dog just can’t stand other dogs, but he never encounters other dogs unless he’s on a leash, you could be dealing with leash reactivity rather than a more generalized aggression toward dogs. It’s best to give your dog opportunities to meet friendly dogs off-leash, if it can be done safely. Do not bring a dog you think might be aggressive to dog parks “for practice.”

Resource guarding can be tricky, because you need to think like a dog when determining what the “resource” is. Lots of people think of food and treats when they think of resource-guarding, but the “resource” can be anything valuable to the dog, including a toy, her human’s shoe, or a favorite lounging spot. Dogs will even fight over who gets to eat vomit!

The important thing to remember is that resource guarding can be dangerous. Far too many dog bites happen because people not only put up with their dog’s inappropriate guarding behavior, but thought it was cute. If your dog “won’t let” your husband sit on the couch next to you, that’s not adorable – it’s a serious problem that requires a professional dog trainer.

Frustration aggression happens when a dog can’t do what he wants and doesn’t handle that disappointment appropriately. For example, let’s say you are holding your dog by his collar to keep him from running outside, and he growls at you, basically being agressive. That doesn’t necessarily mean he’s afraid of being touched; he could resent being restrained because he had other plans for the morning, like rolling in the mud and chasing the neighbor’s cat. You may have experienced a similar dynamic when toddlers are told they can’t have ice cream for breakfast.

A lack of appropriate exercise can also lead dogs to become aggressive as a way to amuse themselves and burn off energy. They might have negative reactions to things that wouldn’t ordinarily bother them, just because they’re bored. (This happens with stir-crazy toddlers too, as I’m sure you’ve noticed!)


Before you invest too much time trying to fi

gure out what is triggering your dog, it’s critical to make sure that he is not suffering from a medical problem. Certain diseases can cause perfectly well-adjusted dogs to start acting in a fearful or aggressive way. Your dog could be panicking because he’s having trouble seeing or hearing, for example. If the problem seems to have developed out of the blue, a vet should rule out hearing and vision issues, as well as chronic pain conditions such as arthritis.

Final Thoughts

Remember that dogs’ perception of the world will always be different from ours. Dogs respond to scents and sounds that our human senses can’t even pick up. There may even be signs your dog is protective of you. But we know there's nothing worse than an uncomfortable and slightly nervous dog. We may never fully understand what these amazing creatures are thinking, but we can do our best to read their signals, and seek out professional dog training when needed.

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