Understanding "Sudden" Reactivity and Aggression in Dogs
Step 6 of 25 in the Dogly Reactivity Channel
with Karen Chapdelaine of TheTimelessDog, Training Advocate

Recorded on
Wednesday, Mar 16, 7 PM EDT

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How to Anticipate It and What to Do When "Sudden" Reactivity and Aggression in Dogs Happens

Are you feeling that somehow out of nowhere your perfectly-behaved dog started showing signs of reactivity or aggression?

Dog parents can often get surprised by a growl or a snap that seems out of character for their dog. Whether it's been a one-time thing or happened more frequently, we all want to understand the why/what/when behind our dogs' behavior so we can support our dogs and avoid high-stress incidents in the future.

Let's jump into understanding reactivity, aggression, and our dogs - and what we can do as their trusted humans to have their backs. (You can watch me talk through all this and answer questions in the accompanying video above of my recorded-live support & learning group on reactivity and aggression with dog parents like you.)


To start, 3 things to know about "sudden" reactivity and aggression...

1) "Sudden" reactivity or aggression in dogs isn't sudden.

2) Dog aggression and reactivity are two separate things.

3) Dogs are talking to us and telling us how they're feeling constantly - we just need to know how to listen.

Bonus fact underpinning all three of the above:

Dogs don't want to behave aggressively. They send us all kinds of signals for our help to get them out of stressful/scary situations so they can avoid resorting to aggressive behavior. We just need to listen.

What's actually happening with your individual dog

As a professional dog trainer, I have many dog owners coming to me for help with their "aggressive" dogs when the vast majority are showing reactive behavior rather than aggressive.

Why the difference between reactive and aggressive behavior matters

Many dogs who are mistaken for an aggressive dog are actually reactive, and they're reacting naturally as fearful dogs. Learning the difference helps you know how to work with your dog. When you know your dog is afraid rather than aggressive, it opens up how you think about and enjoy life with your pup while you're working on any issues.

Reactivity and aggression are two different things. We're reactive as humans; if the doorbell rings, we get up to answer it. We react to the world around us, and so do our dogs. They're not "bad" dogs, they're reacting to what's happening around them.

When it appears to be sudden, when we think it comes out of nowhere, there have already been signs or reasons that we haven't seen. There are all kinds of reactions from dogs for various things. A dog's behavior can include growling or what looks like aggressive behavior but it doesn't always. So although there can be overlap in the outward signs, reactivity and aggression in dogs are two separate things.

What's the difference between reactivity and aggression

Reactivity: showing a response to a stimulus; acting in response to a situation rather than creating or controlling it.

Aggression: hostile or violent behavior or attitudes toward another; forceful and sometimes overly assertive pursuit of one's aims and interests.

What does reactivity in dogs look like?

  • Barking
  • Lunging
  • Looking away
  • Tucking tail
  • Tensing body
  • Hiding

There are different types of reactivity reacting to different triggers - other dogs, humans, on-leash, fear of all kinds of things/situations.

"Sudden" onset reactivity can be caused by:

  • Fear
  • Anxiety
  • Nerves
  • Past experiences
  • Pain - understandably, an injured dog often reacts in "stay away from me" mode (which is why it's good to have your dog learn comfort with muzzles before you ever need to use one in an emergency...you can learn about muzzles here on Dogly).

What does dog aggression look like?

  • Dog aggression looks different for each dog
  • However, it does typically present as growling, snarling, biting
  • Different types of dog aggression: for example, fear aggression, protective aggression, redirected aggression (when a person/dog interrupts some kind of aggression & becomes the redirected object of it), possessive aggression (for example, resource guarding)

"Sudden" onset aggression is extremely rare but can be caused by:

  • Pain
  • Being scared
  • An illness
  • A neurological problem

If you see signs of truly sudden reactivity or of aggressive behavior, consult your vet. We always want to rule out any medical issues that could be influencing concerning or out-of-character behavior. Even relatively minor gut or joint issues can have an impact on your dog's behavior.

Side note - Even more rare is something called "canine rage syndrome." Again, it is extremely rare. In this case, a dog's aggression is characterized by no discernible trigger and a glazed look, lasts for minutes or hours, is believed to be associated with seizures, has a genetic component, and is usually reported between 1-3 years of age. Consult your vet if you see any signs of this syndrome.


The canine ladder of communicating discomfort

Escalating steps in dog body language to watch for

What's usually called "the ladder of canine aggression" - really a misnomer - is actually more about the building signs dogs show in reacting when they feel discomfort in a situation. Being aware of this ladder and getting familiar with each step is extremely helpful in recognizing a situation that could either escalate instantly or build over time.

Worth repeating: dogs don't want to be aggressive!

A growl, a snap, or a bite-miss can all be our dogs' way of telling us loudly that they need space or some kind of help making the threat or threatening situation disappear. Dogs bite pretty accurately and don't usually miss if they want to bite something, so a snap or a missed bite or nip is usually the equivalent of a dog raising his/her voice to a roar to get the threat to back off or get us to pay attention, step in and make it go away.

Here's how the steps progress on the body language ladder (in ascending order from initial to highest intensity signs/actions)

  • Blinks, yawns, licks nose
  • Turns head away
  • Turns body away, sits, paws
  • Walks away
  • Creeps, ears back
  • Stands crouched, tucks tail under
  • Lies down, leg up
  • Stiffens, stares
  • Growls
  • Snaps
  • Bites

If you take a look at the accompanying video above, you can see a graphic illustration of the ladder with each step that's also helpful.

The steps typically play out in this order but over weeks, months, years, if we as their humans don't hear our dogs talking to us, they quit wasting time with the initial steps on the ladder and jump ahead to where they know they'll get attention. That's often when a dog bites "suddenly" - either the dog has learned we won't pay attention to subtle cues and jumps to the end actions, or we humans have missed the lead-up signs in this particular instance. Either way, we can create a different outcome by being observant.

Thankfully, if you have been missing and not responding to your dog's build-up signs and your dog has started jumping right to the end of the behavior progression, you can still change that.

If you start really seeing and hearing your dog, you can give your dog back a sense of trust that he or she can let you know you're needed and you can be counted on to step in. Those earlier steps on the ladder get filled back up as your dog begins to trust that you are watching and have his/her back.

Try this

  • Get to know the steps on the ladder and actively watch for them on your next walk with your dog.
  • Make a mental note of the signs your dog is showing and what triggered them.
  • In the moment, when your dog shows any of these signs, quickly put distance between your dog and the threat. Distance (for example, an emergency u-turn) is your best friend - and you'll find a wealth of more answers and skills in the guides here in the Reactivity Channel to help.
  • Once you're back from your walk, take a moment to record your mental notes in your dog's training plan so you can begin to see patterns and anticipate how to support your dog (Details matter... for example, are all dogs threatening...or just big ones ...how close is too close...?)


General dog body language to be aware of

Really everything matters, since dogs speak to us with the entirety of their body, but to begin, if you focus on your dog's face that will tell you the most. A wagging tail, for example, is not going to tell you much; a wagging tail is not necessarily a sign of a happy dog.

3 cases of body language

(All 3 are photos I've taken of my family/client dogs that you can see in the accompanying video above, along with the Play Bow and Prey Bow examples)

1) CJ in the snow:

What you can see - wrinkled forehead, turned head, no eye contact, raised eyebrow, closed mouth, leaning away from me

What it says: I thought I was just taking a nice photo of CJ in the snow, but he was letting me know he had enough with the photos.

2) Two dogs, smaller Jack on ground on back & Lady standing:

What you can see: smaller Jack - exposed belly, wagging tail, exposed teeth/commissures pulled back; larger Lady - high tail, slight shift forward body, smooth wrinkle-free face

What it says: Often on-back position is saying, "I mean no harm, I'm no threat, please step away," and Jack's exposed teeth add a warning to please move back. Meanwhile, Lady is harmless, just wants to say a nice hi, and doesn't quite know what to do. (If this happened in real life, you would want to gently guide Lady away, introduce some space, de-stressing the situation and letting Jack relax. Then treats all around!)

3) CJ sitting, seeing other dog across the street:

What you can see: CJ leaning forward, alert ears, hard-ish eyes, flared nostrils, closed, tight commissures, whisker beds standing up

What it says: Just seeing the other dog across the street has put CJ on guard, getting him stressed about the dog coming any closer and he's moving up the ladder with his body language saying "make this threat go away."

Decoding your dog's play bow and prey bow

An example of full body language that can be confusing but very useful to know is the play bow vs the prey bow. They look similar but have opposite implications.

Everyone loves to see a play bow (rear in the air, elbows forward touching the ground). It's an invitation to play - a sweet, beautiful thing to see.

With a prey bow, elbows do not touch the ground, they're not playing, they're unsure, with a rigid body and hard stare. Sometimes dogs in prey bow mode are getting low to get small in hopes that the thing doesn't come any closer and goes away. It can also be to get ready to surprise and pounce if necessary. If this happens with your dog, again your best friend is distance. Use your quick, chipper and calm u-turn, then when safely away comfort your dog and shower with treats.

There's one exception on the elbow detail: dogs who play together regularly don't always go into full play bow with elbows on the ground. They're familiar and are more loose and relaxed about it all.


There is so much help for dog reactivity!

Managing reactivity or aggressive behaviors can sometimes seem like a lot but please know there is so much help! You're not in this alone. We're here to help you and your dog get where you need to be to feel comfortable, safe, and happy.

  • Seek out certified professional positive dog trainers and behaviorists like the Training Advocates here on Dogly (beware unfiltered googling)
  • Learn games & activities that are right for your dog (Look At That, 123 pattern games, for ex.)
  • Explore muzzle training - if you are worried about your dog in certain situations, muzzle training also helps with your anxiety which your dog feels at the end of the leash.

Just by being more aware (don't check your phone, don't get distracted), you and your dog both will be more connected and enjoy your walks infinitely more. And remember, every day is different, your dog will have good days and not so good days, you will miss things and make mistakes. Give yourself (and your dog) some grace! Misses happen, just acknowledge them, learn from them, and move on.

Be present and have fun with your dog!

Next up in the Reactivity Channel on Dogly

Now that you have a solid base of understanding of what reactivity is, the causes behind it, and how to anticipate it, you and your pup are ready for what's next. Coming up: management skills and then training techniques to help your dog feel more comfortable in trigger situations of all kinds.

If you have any questions on your dog and reactivity, jump into our Community Discussion. Continue in our Reactivity Channel where you'll learn everything you need to know for your dog from our community of Dogly Training Advocates.

And if you need more individualized training help, get started in your dog's training plan.

Karen Chapdelaine of TheTimelessDog

Training Advocate
Dogly loves Karen because she helps us live life with our dogs in a way that's rewarding, calm, and happy - and does it with empathy.

Karen guides you

Aggression - Basic Manners - Marker Training - Enrichment - Leash Manners - Reactivity

Karen is certified

Certified Professional Dog Trainer Knowledge Assessed (CPDT-KA) - Fear Free Certified - DN-CET (DogNostic - Canine Enrichment Technician)