Understanding the Dog Fight or Flight Response

Updated on November 1, 2019
alexadry profile image

Adrienne is a certified dog trainer, former veterinary assistant, and the author of "Brain Training for Dogs."

Dog fight or flight response
Dog fight or flight response

What Is the Canine Fight or Flight Response?

You may wonder what the dog fight or flight response means. No, it doesn't mean your dog will wear boxing gloves and fight in the ring, nor does it mean he'll grow wings one day and will take off and fly. The canine fight or flight response is an innate survival instinct that humans display, as well.

Fight or Flight Response in Humans

I will never forget the day our physics professor showed up in class began lecturing on the fight or flight response in humans. He was speaking very softly—so softly I felt like nodding off. Suddenly, he took a book and forcefully slammed it on the desk. We all startled and looked at each other wondering if our teacher had gone insane. Then he explained: "This is the perfect example of an adrenaline rush that would stimulate you to engage in fight or flight."

By definition, the fight or flight response is a physiological reaction (not under conscious control) that occurs when an animal or human feels threatened. It was first described by American psychologist Walter Cannon in 1920. This chain reaction causes a cascade of events that is meant to help the body deal with threatening circumstances.

It all starts in the amygdala, which triggers the activation of the pituitary gland. This causes a sudden release of catecholamines such as hormones, as well as neurotransmitters, including cortisone (a metabolite of cortisol), adrenaline and noradrenaline. This leads to a series of changes in the body and mind that we will now examine more closely.

Physiological Changes Caused by Fight or Flight in Dogs

The release of hormones and neurotransmitters during the fight or flight acute stress response causes a variety of physiological changes in the dog. These physiological changes are the body's effort to create a boost of energy sufficient to get the dog out of trouble and survive. While a brief, acute response to a suspected trigger may cause temporary physiological changes, the effects of chronic, prolonged stress in dogs can long term undermine the dog's immune system.

Physiological Changes in Dogs

  • Increased heart rate
  • Increased breathing
  • Increased blood flow to muscles (so the dog can sprint into action)
  • Increased muscle tension
  • Increased blood pressure
  • Increased blood clotting (so to prevent excessive blood loss)
  • Increased blood sugar
  • Appetite suppression (blood flow goes from skin and intestines to muscles for action)
  • Dilated pupils (so to see with more clarity)
  • Heightens your senses
  • Piloerection
  • Inability to concentrate, lack of impulse control, lowered threshold

According to Hans Selye, the Hungarian-Canadian endocrinologist and stress-response scientist, the stressed body goes through a "general adaptation syndrome." After the initial activation alarm phase of fight or flight, the body goes through a resistance phase, where homeostasis works on restoring balance and recovery. This is when the dog "shakes off" the stress so to relax those tight muscles, resumes normal breathing and his heart rate slows down.

The exhaustion phase is then seen if the stress is allowed to continue for some time and the resistance phase is repeated too often, and in this case burnout occurs with its negative effects on the body. The dog's immune system is lowered, cognitive functions (ability to learn) are depleted, energy levels lower leading to lethargy and disrupted sleep patterns. Some dogs may have a hard time relaxing even when there's nothing happening. However, a dog that is acutely stressed may become hyperactive as a defense mechanism before later shutting down.

Choosing Fight Over Flight: Special Circumstances

The choice of fight or flight varies depending on the situation. For instance, a dog who just gave birth to puppies will choose to fight if the puppies are threatened by an animal rather than flee, leaving the vulnerable puppies at risk. Whereas, some dogs may normally flee when presented with frightening stimuli, but may resort to fight if their escape routes are blocked. Genetic predispositions may also play a role. Some dogs breeds may be more likely to choose fight over flight and flight over fight. A learned component may be at play too. A dog who was predisposed to flee may decide to fight first if his attempts to flee were often unsuccessful in the past. This is the dog who stressed by children chasing him and cornering him decides to bite one day to make the chasing stop once and for all.

Other Options Beyond Fight or Flight

Interestingly, when dogs are faced with a perceived threat, they don't necessarily go into fight or flight, they may also have a plan C, a plan D, and a plan E. Basically, the fight or flight response can be extended by adding the freeze, faint and fool around response.

In nature we can see these "Five F" reactions in a variety of animals. A lion feeling threatened will often fight, a zebra feeling threatened may flee, a rabbit feeling threatened may freeze as if becoming almost invisible. The fainting goat is an example of an animal that truly faints when in a state of panic, even though this is not the greatest example as this is mostly caused by a hereditary genetic disorder.

In dogs, signs of fight are pretty evident. The dog may lunge forward, bark and attempt to bite. The signs of flight are also quite evident, the dog may cower behind the owner if leashed or attempt to flee to get out of trouble. During freeze, the dog may stand still, hold its breath and have a fixed look in his eyes. Be careful as a bite may come next. Real fainting is quite rare, but it can be seen when a dog drops to the ground and refuses to budge. Most likely it's a sign of learned helplessness.

The fool around response may sound harmless but it's really a sort of displacement behavior; basically, the dog is taking off the steam from a stressful situation by engaging in a totally different behavior such as rolling on the floor, catering to a sudden itch or humping anything in sight. These are not signs of a disobedient dog who is acting out, but signs that the dog is stressed.

So pay attention to your dog, and try to recognize triggers that may cause the fight or flight response. Prevent these triggers from affecting your dog, and if possible, try help your dog face irrational fears through desensitization and counterconditioning. Your dog's health and well-being will thank you!

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

Questions & Answers

  • Why do some animals flee and some fight?

    I think it depends on natural instincts, but that there is also a learned component. For instance, it is instinctive for zebras to escape rather than fight a hungry lion. Prey animals are known to choose flight because they can't stand a chance to survive animals that are larger or stronger or who hunt in packs. Fighting back would be maladaptive unless they have no other options. An example of a learned component? A dog may choose to remove himself from a situation and therefore choose flight, but that day he is cornered, he may have to resort to fight.

  • When a dog is fighting and he draws blood from his victim, is it true that once they get the taste of blood, they will continue to kill ?

    No, that is an old myth, meaning that the taste of blood won't make a dog more likely to injure or kill in the future. The taste of blood, in other words, won't make a dog a crazed killer. However, a dog who uses aggression may be likely to use it again if put in a similar situation in the future. A dog who acts aggressive, needs evaluation by a professional such as a board-certified veterinary behaviorist.

© 2013 Adrienne Farricelli


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    • alexadry profile imageAUTHOR

      Adrienne Farricelli 

      2 years ago

      Hello Elizabeth, bless your heart for helping this dog. Xanax on its own can help take the edge off but you will need behavior modification along for the ride. Counterconditioning entails creating positive associations with triggers and is best when done along with desensitization. Here's a read explaining this: https://pethelpful.com/dogs/Dog-Behavior-The-Power...

    • profile image

      Elizabeth Shaheen 

      2 years ago

      This is very interesting, I have a question...I have a two year old female chocolate lab that I got when she was just a year old. She came from a broken home of father, mother and five year old child - there was a devoice and the father was left with the dog. He choose to find her a home because he said his job causes extensive travel and the dog had to be " kennaled for long periods of time. .Lucy seems to have some fear issues she has been put on Xanax by our vet but Lucy still has some fight or flight issues. . You spoke of counter conditioning. How do I do this ???


    • alexadry profile imageAUTHOR

      Adrienne Farricelli 

      2 years ago

      It could have been triggered by competition or a phenomenon known as predatory drift. Be careful with these two dogs together as this may repeat.

    • profile image


      2 years ago

      Tonight my German Shepard just attracted my fiancé’s chawennee. They have been best buddies for 6 months. I took her outside to go to the bathroom. I brought her in. My fiancé was playing on the floor with her dog. My Shepard just walked up and attacked the little dog. Totally unprovoked. There was no growl nothing to see it coming. Would of killed the little dog if we weren’t there. What would cause that action?

    • profile image


      2 years ago

      do they ever stop when the other dog is down or do they continue?

    • alexadry profile imageAUTHOR

      Adrienne Farricelli 

      6 years ago

      There's always something new to learn about dogs. Every dog I deal with always teaches me something new. It's awesome!

    • JamesWhitaker profile image

      James N. Whitaker 

      6 years ago from Dallas, Texas

      Even my two dogs have a small fights due food aggression. However little by little we manage how to deal with that fights. Your have though me something about understanding dog behavior. Thanks!

    • profile image


      6 years ago

      whoah this blog is excellent i really like reading your articles. Stay up the good work! You already know, many persons are looking around for this info, you could help them greatly. degfedacdcfe

    • profile image


      6 years ago

      Only wanna tell that this is very useful , Thanks for taking your time to write this. dfdbdggddekb

    • Monis Mas profile image


      7 years ago

      Fantastic information. My dog is always ready to protect (himself and his humans) and never backs down :-(. I had to break a fight once, and it was scary.

    • alexadry profile imageAUTHOR

      Adrienne Farricelli 

      7 years ago

      Hi Mideget38, a great comparison, I have heard that saying as well many times! thanks for stopping by!

    • midget38 profile image

      Michelle Liew 

      7 years ago from Singapore

      I think this is the reason why people say that when put in a corner, they fight. We hear that timelessly. Definitely see that in our doggies! Glad to share dog hubs with you, Alexadry!

    • alexadry profile imageAUTHOR

      Adrienne Farricelli 

      7 years ago

      Larry, I didn't know that. That's quite interesting as I never would have imagined that saying came from that, thanks for sharing; your insights are always interesting and fun!

    • alexadry profile imageAUTHOR

      Adrienne Farricelli 

      7 years ago

      Hi Kristen, glad to hear this hub helped add new information about the flight and fight response in dogs! Yes, it's very important especially since long term, chronic stress can lead to serious health problems.

    • Larry Fields profile image

      Larry Fields 

      7 years ago from Northern California

      Hi alexadry,

      Well done. Voted up and interesting.

      I've read that opossums can have an extreme fainting response. In life-threatening situations, when neither fight nor flight is an option, they actually lose consciousness, and produce a terrible stench. They look and smell dead. Hence the American expression: "playing possum."

    • Kristen Haynie profile image

      Kristen Haynie 

      7 years ago from Scotia, CA

      Great hub! I always knew the fight or flight instinct existed in people and many animals, but I never knew quite how it worked! Thanks for covering this subject so thoroughly! I think it's important that people understand just how this works, so maybe they can better understand why some dogs react the way they do in times of high stress or fear.


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