Why Is My Dog Aggressive When Woken Suddenly?

Is my dog normal?
By Emma Bowdrey, May 2020
Dog With Sleep Startle Reflex

“Let sleeping dogs lie” is never more apt than if you have a dog that reacts when startled during sleep. For owners that are new to this scary reaction, it can be quite worrisome, especially if there are children, elderly or anyone with learning disabilities in the family.

Most people could understand and forgive a dog who lashes out when suddenly trodden on or struck by something falling on them as they slept. Although many dogs are likely to just move away in these circumstances. It is this kind of accommodating behaviour that has led them to become part of the family and our best friends.

However, a proportion of dogs can growl, snap, lunge, and bite when woken unexpectedly. For these dogs, a simple kiss on the head can trigger this reaction and it can be momentarily terrifying.

Sleep Startle Reflex In Dogs

The startle reflex is instinctive in wild animals. There are many dangers to which they need to react quickly. Assuming that the disturbance is a foe rather than a friend is far more practical. The seconds that it takes to access what woke you could mean life or death for many animals in the wild or out on the streets.


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Domestic dogs still carry some of these wild traits and it’s not uncommon for a sleeping dog to attempt a bite when startled awake by touch, movement or noise. Greyhounds are one dog breed that is known to commonly carry this reflex. My first adopted Greyhound Tipps had a sleep startle reflex and it took me some time to get used to it. Tipps liked to sleep with his head on my lap or perhaps nuzzled into me on the sofa. If I moved my hand stroking him or nudged a bit to get comfy, he often woke up snapping and growling an inch from my face. I can say firsthand that it can be shocking and scary.

Dogs enter into REM quicker than humans. It is impossible to know how deeply your dog is sleeping and what will startle them awake. This is why sleep startle reflex can be quite alarming. In almost all cases, your dog will see within a second or two that it was just you and will immediately stop. It is important to note that this reflex when woken is a reaction and not aggression. Dogs who have sleep startle reflex are not consciously attacking. 

How To Manage A Dog With Sleep Startle Reflex

Anyone with a dog who suffers from sleep startle reflex must first accept that it is just the way they are. It cannot be trained out. It certainly cannot be resolved using any form of punishment. Shouting, scolding or physically reprimanding them will not cure this condition. It is more likely to create a fear of falling asleep as your dog worries whether they will be unexpectedly woken and punished. Dogs will not be able to associate the reaction to the punishment as it was not conscious or deliberate. They will associate sleeping with the punishment.

My best advice is to manage it responsibly and without placing stress on your dog. Finding a gentle method to rouse your dog without startling them is key to this. Dogs will typically take naps throughout the day but this sleep is not always deep.

  • Calling their name calmly and quietly can stir them enough to then move near or around them.
  • Advise family, friends, and visitors who are likely to come into contact with your dog while they are sleeping that they have this condition.
  • Educate children that they should not disturb a sleeping dog, especially not someone else’s. They should always ask before approaching.
  • Provide a safe space away from footfall for your dog to sleep undisturbed.
  • If necessary, use a muzzle when in public to prevent a scary situation from occurring. Not all people will be aware of sleep startle reflex and dogs are quickly blamed for what looks like aggressive behaviour.
  • You may be able to condition your dog to respond positively to being tapped on the shoulder or forearm with training. Choose a spot on your dog (avoiding the head) that you want to use as the wake nicely trigger. Tap this spot and reward with a delicious treat. Do this over and over while your dog is awake so that they associate being tapped on that spot with positivity. Gradually move on to trying this when they are partially asleep and fully asleep.

Work with your dog to find out the best solution for them. This is a small flaw in what is a great family member and can be easily managed.

Emma Bowdrey is an ISCP-trained Dog Trainer based in Prague, where she lives with her adopted greyhound, Swift. Emma has worked with dogs since gaining her qualification in Canine Behaviour & Psychology and now runs her own business - Four Long Legs. Emma uses positive reinforcement methods to make each hound a happy one.

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