What is Trigger Stacking?

Updated: Jul 1

Has your dog ever displayed a stronger-than-usual reaction to something like another dog or person? Maybe he growled at a guest or snapped at a dog walking by. Maybe he even bit someone. Your dog may have been experiencing something called 'trigger stacking.'

In this article:

  1. Defining Trigger Stacking.

  2. How Trigger Stacking Affects Dogs.

  3. Recognizing and Preventing Trigger Stacking.

Defining Trigger Stacking.

Trigger Stacking is the combination of multiple stressful events in a short period of time, leading to an extreme reaction to a small stimulus.


A stressful or scary situation has a physiological effect on a dog. When a dog experiences a stressful event, he experiences, among other things, an increase in cortisol levels - the stress hormone associated with the 'fight-or-flight' instinct. It can take around 72 hours for those hormone levels to return to normal, and in that time period, the dog is particularly sensitive to additional stress.


How Trigger Stacking Affects Dogs.

Thinking about the way in which stress affects our own lives can be helpful in understanding how it affects our dogs.


Think about all of the things that cause you some amount of stress during the average day at work; oversleeping, spilling your coffee, getting stuck in traffic, that one annoying coworker who won't stop talking, your boss in a bad mood, getting stuck at work later than you planned. On any given day, one of these things happening is stressful and annoying, but you're likely able to get through your day.


Imagine, though, that a number of these things happen in one day. You oversleep, and as you rush out the door, you spill your coffee on your new shirt. When you get to work, your annoying coworker is waiting for you at your desk and won't shut up, and then your boss storms over to scold you for being late. You get stuck in traffic on the way home. When you walk in the door, your spouse asks you about your day, and you snap at them to leave you alone.


From your spouse's perspective, you just snapped at them out of nowhere for something that you usually don't mind, but from your perspective, their question was the last straw to your already stressful day.


Now, think about your dog. There are a number of things that he finds stressful in any given day - even if some of those events are things that he usually tolerates or enjoys (maybe you don't mind talking to that annoying coworker on good days; maybe your dog doesn't mind meeting kids on good days).


Every dog is different, and what a dog finds stressful is up to him - even if it's something that we don't think is stressful or scary. Some of those things may include the following:

  • loud noises (like thunder, fireworks, a car backfiring, etc.)

  • interacting with kids

  • strangers coming to the door

  • being cornered

  • having his ears cleaned or nails clipped

  • having a toy taken away

  • being barked at by another dog

  • a new pet at home

  • visitors staying at the house

  • riding in the car

  • going to a new place (or somewhere with negative associations, like the vet)

  • a family member going out of town

  • a change to his normal daily routine

  • pain or illness

  • a whole slew of other events


Imagine that your dog starts his day with a walk around the neighborhood, and a big truck backfires nearby. When he gets home, the neighbor dogs are barking at him, and then a stranger knocks on the door to deliver a package. You corner him in the kitchen to clean his ears, and all of a sudden, he snaps at you.


From your perspective, he just snapped at you out of nowhere for something that he usually doesn't mind, but from his perspective, being cornered for an ear cleaning was the last straw to his already stressful day.


Recognizing and Preventing Trigger Stacking.

So how do we recognize trigger stacking and prevent our dog's stress level from increasing to the point of growling, snapping, or biting?


Recognizing your dog's body language is a huge step to keeping him safe and comfortable. Below, you'll see the 'ladder of aggression,' a graphic that outlines a dog's stress signals, from low level signals (lip lick, head turn) to major signals (growling, snapping, biting). If we can catch those low level stress signals and remove our dog from the stressful situation, we can avoid escalation in behavior.

It's important to remember that every dog is different, and each individual dog will favor the signals that have been successful for him in the past (i.e. made the stressful thing go away). If low level signals like yawning or walking away have been ignored or punished in the past, the dog may jump straight to cowering, stiffening, or even growling or biting.


While in most cases, a dog biting 'out of nowhere' is actually a case of the human not recognizing the dog's communication, it's also possible that the dog has learned that giving a warning is ineffective. This is why it's so important that we respect what our dogs are telling us and avoid punishing things such as moving away from us and growling.


We love this video on trigger stacking by Donna Hill, which gives another example of what trigger stacking may look like.

For examples of enrichment that can be used to help lower a dog's stress levels, check out the 'Enrichment' section here.


Have training or behavior questions? Contact us!


Author: Margo Butler, CPDT-KA