Trigger Stacking

The Last Straw!
By Abby Huxstable

Have you ever found your dog reacting in a situation they wouldn’t usually react to? Or have they suddenly had a severe reaction to something they aren’t usually bothered by? You have no idea why they have suddenly reacted like this when they wouldn’t normally. Well, this
reaction is likely due to trigger stacking.

My favourite analogy for this is a bucket. Your dog’s bucket holds ten litres of water. Every event in your dog’s life adds or takes water out of their bucket. However, if the bucket reaches that ten litres, it will overflow, and your dog will reach their threshold and react.


Each dog will have different values to things they experience. For example, food may be one litre, play may be one litre, the postal delivery or doorbell may be three litres, a cat could be two litres. A calming activity like scent work may be minus one litre, chewing may be minus one litre, a massage from your owner may be minus one litre.

The other key thing to remember is that cortisol is a stress hormone. This is produced in our dogs in exciting or stressful times and can take up to 72 hours to leave their bodies. That means you need to consider your bucket over a 72-hour (three day) period and even longer if you have a series of threshold events.

Let’s look at this in a real-life scenario. Most dogs will hover around four or five litres in their buckets most of the time. This gives them a good capacity for additional stress events before they reach their threshold. Even if the dog were to wake up with their bucket completely empty, they then have their breakfast (+1L) and have a play with their owner (+1L = 2L in bucket). They then have a sniff in the garden (-1L = 1L in bucket). The owner takes the dog for a walk and they see a cat (+2L) then a tractor (+2L = 5L in bucket). This is still fine; they can cope with all of this. When they get home from the walk, they have an enrichment activity while owner is busy (-1L = 4L in bucket).

However, then a repair worker comes to the house (+3L = 7L in bucket), closely followed by a parcel delivery (+2L = 9L in bucket). We are now very close to threshold, but the dog still hasn’t gone over their capacity. As the owner doesn’t know about trigger stacking, they aren’t aware that they might need to manage the dog’s exposure to stress.

They head out on their afternoon walk and it is a nice sniffy walk (-1L = 8L in bucket), but then at the end of the walk they see another dog, who barks at them as they approach (+3L = 11L in bucket!!). Oh dear; our dog barks, lunges and is pulling on the end of the lead.

Our poor owner is shocked and mortified and says the common, ‘I’m so sorry, he doesn’t usually react like this’. However, both dogs were on leads so there’s no real harm done. Both owners move on. Our owner wonders if it was something about the other dog that triggered them, as they are usually fine with other dogs, although a bit more wary if the other dog barks.

No! It was trigger stacking. Those events over this past day have overflowed our dog’s bucket. This same scenario could have played out over the space of three days with the same result (although it’s likely there would be more activities that empty the bucket).

Obviously, if you have a dog that is reactive to several triggers, they will have a much fuller bucket in general and reach their threshold much quicker. This is why we recommend at least three days off after a stress event to really ensure that bucket is fully empty before we expose our dogs to more stressors.

This is also why we work with our dogs to desensitise them and counter-condition them to triggers. So, instead of a trigger being worth four litres, it is maybe only one or two litres. You see this as you work through counter-conditioning. Your dog reacts less and recovers quicker from stress events as the litre value of the trigger reduces.

We also use plenty of calming activities, those licking, sniffing, and chewing activities, plus enrichment activities (as long as they are not frustrating or exciting for our dogs), to reduce the amount of water in our dogs’ buckets. Of course, time itself will allow that cortisol to dissipate and the water to naturally evaporate from the bucket.

Therefore, if your dog has an unexpected reaction to something that doesn’t usually bother them, think back over your last few days. What events have occurred that could have contributed to filling that bucket?

If you have a reactive dog, who you know has several triggers, give them plenty of time off between exposure to these triggers to allow that bucket to empty. This way, you prevent them from reaching threshold.

Plan your desensitisation and counter-conditioning sessions so there are calming activities in between, as well as time off. Don’t risk pushing them over that threshold by exposing them to too many triggers in a short space of time.