Understanding Dog Aggression & Reactivity

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Learning Objectives

In this lesson you will learn:

  • What it means when a dog is ‘reactive’
  • Some methods for working with reactive dogs
  • What it means when a dog is ‘aggressive,’ and why you should not accept aggressive dogs as clients
  • What a trigger is and what ‘over threshold’ means

Dog Aggressive and People Aggressive Dogs

A dog aggressive dog, as we define it here, is a dog that has caused physical harm to another dog. I do not recommend taking on dogs that are dog aggressive, because if a dog has caused physical harm to another dog, it is not a far leap for a dog to be aggressive towards a person. This is especially the case in a pet sitting situation where there might be other stresses and triggers, such as an altered routine and new people coming into the home, which can bring the dog closer to, or even over, threshold.

People aggressive dogs, as we define them, are dogs that have caused physical harm to a person.  If the client tells you a dog has been aggressive towards a person, again, I do not recommend taking on that client. It is better to be safe than sorry. Do not put yourself in a situation where you may be hurt.

Refer Aggressive Dogs to an Animal Behaviorist

I recommend screening for aggression issues during the initial sales call, rather than waiting for the meet & greet to talk about these issues.  

If a client mentions their dog has aggression issues, I refer those clients to a local Karen Pryor Certified Training Partner or an Animal Behaviorist who I trust. I would much rather recommend the dog gets the help and rehabilitation they need, rather than put myself or a sitter in danger by caring for an aggressive dog.


Dog attacks are serious, and can cause permanent damage and disfiguration to your face, limbs, hands, and body. Take dog aggression seriously.

Reactive Dogs

First, let’s define what I mean by a reactive dog. A reactive dog may bark, become stressed, fearful, or overly excited at the sight of, or proximity to a trigger. Reactive dogs become over threshold more easily than other dogs. 

Reactivity can be thought of as a spectrum. Some dogs are very reactive to certain triggers, and may become over threshold very easily in the presences of only one trigger. A dog on the other side of the reactivity spectrum might only become over threshold when many  triggers occur at the same time. 

It is important to note that reactive dogs, as we are defining them here, have:

  • Never caused physical harm or damage to another dog
  • Never shown aggression towards a human

Caring for reactive dogs is rather common in the pet sitting field. Reactive dogs tend to not do well at the kennel or at doggy daycare because of the many triggers present at those facilities. So, clients with reactive dogs tend to look for private dog walkers or pet sitters to care for their dog.

Understanding Triggers

Since it is common for professional pet sitters and dog walkers to work with reactive dogs, let’s take a few moments and cover what a “trigger” is, and what is meant by “over threshold”.

If you talk with an animal behaviorist, they will have more complex definitions of stress, arousal, triggers, and threshold than what we are going to cover here. And, if you want to become an animal behaviorist, you are going to need to know all of those definitions and how they interact with one another. But, for professional pet sitting and dog walking, we can keep it simple. So, for this course, we are going to cover the basics of what you need to know to manage triggers and how to prevent a dog from becoming over threshold so you can keep the pets in your care safe and stress free.

First, let’s define triggers in the context of professional pet sitting and dog walking. Here we are defining a trigger as anything in the dog’s environment which causes the dog to feel stress, pain, or fear.  

Some common triggers are:

  • A dog barking
  • Unfamiliar people
  • Other dogs (familiar or unfamiliar)
  • Wild animals
  • Loud noises, such as fire alarms, horns, construction
  • Traffic
  • Certain smells like, smoke, alcohol
  • People with hats, beards, or hoods
  • Bikes or skateboards
  • Certain events or experiences
    • Such as fireworks displays
    • Going to the vet
    • An altered routine
    • Busy areas
    • Walking routes on which the dog had a bad experience
Again, it is important to note that not every dog will be triggered by the same things. Some dogs will be very easily triggered when exposed to just a single trigger and other dogs may not be trigged at all even when experiencing many triggers all at once. 

Trigger Stacking - The Tea Kettle Analogy

Now that you know what a trigger is, let’s take a look at how triggers can interact with one another.

When there are multiple triggers present in a dog’s environment, the triggers are said to “stack up” and if there are too many triggers stacking up, they can cause the dog to become over threshold.

To explain how trigger stacking works, I like to use the tea kettle analogy.

Imagine a tea kettle, or just look at the tea kettle in this video! Now, imagine each trigger as a candle. When the trigger is in your dog’s environment, it’s like placing that candle under the kettle. 

If there is just one candle, it would take a while for the water in the kettle to boil over. Just like for some dogs, if there is only one trigger, they may be able to cope with it and not show signs of fear or stress. 

But as the dog is exposed to multiple triggers over time, it’s like adding more candles under the kettle. So, the water heats up faster.  Eventually, if there are too many candles under the tea kettle, the water boils over, similar to how a dog might become over threshold in a stressful environment with too many triggers.

It is important to note that all of the triggers do not need to be happening at one time to cause a dog to go over threshold. When a dog is exposed to a trigger, it activates a hormonal and neurological response that can last for at least 24 hours following a stressful event. So, trigger stacking can occur over a period of hours or even days. 

The goal should be to avoid triggers altogether. Be on the lookout so you can avoid triggers that may stack up and cause the dog in your care to go over threshold. 

Add Distance to Reduce Triggers

When working with dog reactive dogs, you can usually just avoid other dogs and other triggers by adding distance between the dog and the trigger. For a dog, distance from the trigger means safety because in the dog’s mind, when the trigger is farther away, it poses less of a threat. 

My mantra when I am walking a client’s dog is: Avoid, Avoid, Avoid. Avoid all problems. I am always on the lookout for potential triggers and problems while out for a walk. If I see anything that could possibly be a trigger for a dog, I just try to get as far from the trigger as possible. 

This might mean walking across the street, if possible, or even walking back the way I came, or finding an alternative route.

In cases where I absolutely must walk past the trigger with the dog and there is no other option, I will:

  • Try to distract the dog with a tasty treat
  • Speed up our walk and jog past the trigger
  • Try to get the dog to focus on me rather than the trigger

If approved by your client or the owner of your company, one of the best ways to help a dog that becomes over threshold easily is to train eye contact by using a clicker and a reward.

Understanding Threshold

When a dog reaches threshold, they are no longer able to cope with the stresses in their environment. They often reach a fight, flight, or freeze state. A dog that is over threshold may be:

  • Panting heavily 
  • Yawning 
  • Have an increased heart rate 
  • Barking
  • Lunging
  • They often are not able to focus

When a dog becomes over threshold, their prefrontal cortex, where higher-level processing and thoughts occur, becomes overloaded and the dog is no longer able to make rational decisions or learn. It is not possible to train a dog while they are in an over threshold state. 

As a dog walker or pet sitter, it should always be your goal to not get a dog into a situation where they might become over threshold. If you ever do encounter this situation, try to add distance between you and the trigger, distract the dog, and try to jog away from the trigger. 

Even after a dog has come back down below threshold, you may want to cut the walk short and go back to the pet’s home and try to calm them down.

Why Pinch Collars and Shock Collars Can Cause Aggression

So, what causes these reactivity issues in the first place? Many times reactivity issues are caused by improper training that use fear or pain. That is why we at Certified Pet Expert advocate for no use training that involves fear or pain, and we advocate for no use of pinch collars, electronic shock collars, or other training tools or collars that cause pain.  We also believe, as a certified professional dog walker or pet sitter, it is important to understand how these collars and any training tool that uses pain, can lead to aggressive, or otherwise negative tendencies. 

Dogs do not problem solve in the same way we do. A dog’s prefrontal cortex is much smaller than a human’s, meaning a dog’s mind has less computational power. An example of this would be when a dog wraps their leash around a pole, and no matter how hard the dog tries, they can’t quite figure out how to free themselves. Most humans could easily get themselves out of this situation, but some dogs will not understand it is the leash constraining them.

A similar error in problem solving happens when humans train dogs with a pinch collar, which causes pain at the moment a dog pulls on the leash.

Think about the scenario that is set up when a dog pulls on the leash, and experiences pain from pulling on a pinch collar. The dog:

  • Sees another dog
  • Wants to run towards the other dog to say ‘Hello’
  • Gets pinched around their neck
  • Feels pain
  • Because of limited problem solving abilities, the dog associates seeing another dog with pain around their neck
  • The dog develops a fear of other dogs, because they do not want pain around their neck
  • The dog starts barking at other dogs, or acting aggressive to get other dogs to stay away

Tragically, some dogs trained with pinch collars spend their life thinking the actual sight of the other dog is causing the pain. 

We have seen some level of dog reactive behavior in 100% of the dogs we have walked that have been trained with the use of a pinch collar. Some level of dog aggression, or serious dog aggression, is common in many of these cases. Although, sometimes it takes months before the aggressive behavior will reveal itself. 

I was curious why some dogs do not show this aggression until a “perfect storm” situation arises. So, I reached out to my friend who is a Karon Pryor Certified Dog Training Partner, to ask this question. She told me the reason some dogs do not show aggressive behavior even though they have been subject to aversive training methods is because they are potentially more resilient than others, and are better at hiding their emotions. Tragically, the dog feels the same internal fears, and experiences the same trauma and stress. 

It is important to note that training with a pinch collar, e-collar, or leash corrections, is unnecessary. In all cases, clicker work is more effective. Please help spread awareness of this by encouraging the owner of your company to not accept clients who insist on using a pinch collar or electronic-collar. Instead, we recommend the Pet Safe Easy Walk harness. 

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