Why does my dog growl in his sleep, and when should I worry?

It is eleven at night. Your dog is stretched out asleep on the rug when he starts to growl softly, lips trembling, paws paddling as if he were running somewhere. Out comes a muffled bark with his mouth barely open. You look at him and cannot decide whether to laugh or worry. Another evening, another scene: you lean over to stroke him while he sleeps on the sofa, he wakes with a start, growls at you or snaps at the air. Same sound, different situation. The first is almost always a dog having a dream. The second is a dog startled awake, and that one needs some work before somebody gets bitten.

Why dogs growl in their sleep

He is dreaming

Dogs have a stage of sleep in which the brain is very active, the eyes flick about under the lids and small muscles twitch. It is the rapid eye movement stage, known as REM sleep. That is when you hear the muffled growl, the short bark, the whimper, and see the paws "running", the tail thumping and the jaw chewing on nothing. In rats, researchers have watched the sleeping brain replay the routes the animal ran during the day. Your dog is very probably replaying his day too: the ball in the park, the dog on the corner, the trail he worked that morning.

An ordinary dream is easy to spot. The body stays loose, the movements are small and brief, and the whole thing lasts anywhere from a few seconds to a minute or two. Call his name and he wakes quickly, looks at you, maybe wags, and settles back down.

He woke up frightened

A dog in deep sleep who is touched without warning can wake up scared and react before he has worked out where he is. He growls, leaps up, snaps. The old saying "let sleeping dogs lie" is right. Older dogs who hear or see less well get caught out more often, because they never heard you coming.

He is guarding his spot

Some dogs growl when someone comes near the place they are resting, especially the sofa or the bed, even when they are half awake. He is not dreaming and he has not been startled. He values that spot and does not want to lose it. It is a close relative of guarding food and toys.

Something hurts

A dog with sore joints or a bad back may growl when touched or moved in his sleep, quite simply because being touched hurts. If he only growls when you touch one particular area, or only since he started limping, pain is the first thing to think of.

Less often, a sleep disorder or a seizure

A few dogs move violently in their sleep: running flat out, biting at nothing, crashing into walls, and they are hard to wake. Others have epileptic seizures that start during sleep. There is more on both below, in the medical section.

What does not work, even when it seems to

Shaking him out of a "nightmare". A dreaming dog is not suffering the way you might imagine. A sudden touch is exactly what can turn a dream into a fright bite, especially when it is a child leaning in with their face right by his muzzle.

Telling him off for growling when he wakes. The growl is a warning: you scared me, back off. Punish it and he will be just as frightened next time, only he will skip the warning. He may go straight to his teeth.

Hauling him off the sofa when he growls there. You risk a bite and you confirm that the spot really does need defending.

Letting children cuddle him while he sleeps. It looks sweet and makes a nice photo, but it is one of the situations in which children are bitten most often.

Putting it down to a bad dream every time he growls at you. If it keeps happening when you approach his spot, it is a different problem with a different fix.

The plan, step by step

1. Find out what is really going on

Film a few episodes on your phone from where you are, without touching him. Note whether he was deeply asleep or just dozing, where he was, what you did just beforehand, how long it lasted and how he woke. After a week it is usually clear: a dream, a fright, guarding his spot, or something odd that needs a vet.

2. If he is just dreaming

Let him dream. If you do want to wake him, call his name from a metre or two away in your normal voice, without touching him. Only move closer once he has opened his eyes and looked at you.

3. Waking him without a fright

• House rule: nobody touches a sleeping dog. Call him, wait for him to wake, then go to him.
• With an older dog who does not hear well, tap the floor gently with your foot so he feels the vibration, or switch the light on, before you approach.
• Give him his own sleeping place in a quiet corner, away from the routes everyone walks through the house. The hallway and the spot by the front door are poor choices.

4. If he is guarding his spot

• For a few weeks, the sofa and the bed are off limits. Close the bedroom door and put something on the sofa while you are out.
• Set him up a really good bed on the floor next to you: a soft blanket and a chew he only gets there.
• Teach him to hop down on a cue with a tasty treat tossed onto the floor. Say "off", toss the treat, he jumps down after it, and you praise him warmly. Once he gets off every time, toss the treat only after he has landed. Stop moving him with your hands.
• If he still growls, get help. The page on resource guarding goes into more detail.

5. Children

Spell the rules out and repeat them until everyone knows them: we do not touch the dog while he sleeps, we do not hug him, we do not lie down next to him. His bed is his alone. Whenever small children and the dog share a room, an adult is there too.

The first week

When it is a medical problem

Dreaming is not an illness. A few things that happen during sleep, though, call for a visit to your own vet, with the video on your phone:

• He does not wake when you call loudly or switch the light on. His body is rigid rather than loose, shakes rhythmically, he drools heavily, wets or soils himself. Afterwards he is confused, wobbly and does not seem to know you for a few minutes. That may be an epileptic seizure.
• Violent movements in sleep: running flat out, biting the air or whatever is in reach, hitting things, falling off the bed, then waking with difficulty. Vets have described a sleep disorder in a small number of dogs in which the body acts the dream out for real. It can sometimes be treated.
• New growling when touched, in a dog who never used to, especially an older one. Think joints, back, ears or teeth.
• An older dog who seems lost when he wakes, wanders aimlessly at night or sleeps differently from before. It may be brain ageing.
• Noisy breathing in sleep, new snoring or pauses in breathing, particularly in short-nosed breeds.

Your vet will learn more from a video than from any description. Show a whole episode, from the start until after he has woken up.

When to call in a professional

• he has bitten or snapped at someone on waking, especially a child;
• he growls more and more often when people approach his spot;
• he does the same when awake, if you go near his food or toys;
• you have small children and cannot be sure the "no touching while he sleeps" rule holds at every moment;
• you cannot tell from the footage whether it is a dream, a fright or something else.

A trainer or behaviour specialist will look at the videos and at your home: where the dog sleeps, where people walk, who leans over him and when. They help you set things up so nobody gets caught by surprise again. If they suspect a medical cause as well, they work alongside your own vet.