Why Do Dogs Sleep With Their Mouths Open?

If you have a dog, you may have noticed them sleeping with their mouth wide open, tongue lolling out one side. This silly sleeping position can look funny and make you wonder why they do it.

If you’re short on time, here’s a quick answer: Dogs sleep with their mouths open to regulate their body temperature more easily. The mouth opening allows faster panting and heat exchange.

In this comprehensive article, we’ll explore the reasons for this common dog sleeping position in more detail, looking at temperature regulation, airway issues, breed tendencies, and when an open mouth may indicate a health problem.

Dogs Open Mouths to Regulate Body Temperature

Dogs don’t have as many sweat glands as humans do and rely more on panting to cool themselves down. When they get too hot, they open their mouths to pant which allows evaporation of moisture from the mouth and tongue, releasing excess heat.

This is an effective way for dogs to control their body temperature.

Panting Releases Excess Heat

Panting is a critical mechanism dogs use to avoid overheating. By breathing rapidly through an open mouth, air passes over the moist surfaces of the mouth and tongue, allowing evaporative cooling to take place.

This evaporation of moisture carries heat away from the body, bringing down the dog’s core temperature. Panting is such an effective cooling method that dogs can lower their body heat through panting even in humid environments when sweat evaporates less readily.

Some Breeds Prone to Getting Overheated

Certain breeds like Bulldogs, Pugs, and Shih Tzus have shorter snouts and narrowed airways making panting less efficient for them. Overheating is a real risk for these brachycephalic (short-nosed) breeds. They’ll really struggle in hot weather and need ample shade and water.

Small toy breeds also have trouble regulating their body temperature. Their tiny size makes them prone to getting dangerously overheated.

Young Puppies Can’t Regulate Temperature Well

Puppies also have less ability to maintain their body temperature compared to adult dogs. Without a fully developed temperature regulation system, puppies can overheat quickly. This is especially true for newborn puppies who rely on snuggling up to mom and litter mates to stay warm.

An orphaned puppy or one separated early from the litter could suffer temperature regulation problems. Panting helps compensate but puppies still need special care in temperature extremes.

Brachycephalic Dogs May Have Breathing Issues

Some dogs, especially those with short muzzles called brachycephalic breeds, are prone to breathing issues that can cause them to sleep with their mouths open. Brachycephalic dog breeds include Bulldogs, Pugs, Boxers, Boston Terriers, and Shih Tzus.

Short Muzzle Causes Airway Obstruction

The shortened muzzles of brachycephalic dogs can obstruct their airways and make breathing difficult. Their nostrils are often too small, their soft palates too long, and their windpipes narrower than in dogs with longer muzzles.

During sleep, when muscles relax, their airways can become even more obstructed.

Gravity Helps Open Airway When Lying Down

Lying down with the mouth open allows gravity to help pull the tongue and soft tissues away from the entrance to the trachea (windpipe). This helps open the airway more for easier breathing. Sleeping upright or with the mouth closed can further obstruct some brachycephalic dogs’ airways.

According to the New York Times, over 57,000 brachycephalic surgeries were performed in the US in 2021 to help improve breathing and quality of life.

Surgery Sometimes Necessary for Severe Cases

For dogs with severely obstructed airways, surgery may be recommended. Common surgeries include nostril widening, soft palate reduction, and correction of windpipe issues. While not curative, these can help open the airway more.

Lifestyle changes like weight loss and avoiding hot weather can also help brachycephalic dogs breathe easier.

Mouth Position Varies by Sleep Stage

Jaw Relaxes During REM Sleep

When dogs enter the REM (rapid eye movement) stage of sleep, their jaw and facial muscles relax. This allows their mouth to fall open passively as they dream. It’s common for dog owners to see their pet’s mouth hang agape, with tongue lolling out during this sleep phase.

Saliva may pool in the back of the throat, causing subtle snoring or gulping sounds.

According to pet experts, the reason a dog’s mouth tends to relax more in REM sleep ties back to their wild origins. When wolves and early canines would bed down in dens to sleep in groups, they felt safe enough to completely relax their jaw.

An open mouth allows for deeper, more restorative sleep after a long day of hunting and ranging over territory.

Twitching Indicates Vivid Dreaming

Along with a gaping mouth, you may also notice twitching lips, whiskers, and facial muscles on your sleeping pup. These spasms indicate that your dog is likely dreaming during REM sleep. The technical term is “activated sleep” since your dog’s brain is firing rapidly behind their closed eyelids.

Dogs spend about 10-15 percent of their shut-eye time in the REM phase. If they’re making movements like running or biting, chances are they are in the midst of an exciting dream!

As illustrated in the chart, the characteristics of REM sleep differ quite a bit from other sleep stages. The dog’s brain is nearly as active as when they’re awake, even if their body appears completely at rest.

Common to See Teeth in Deep Sleep

In the deep sleep stage, which occurs earlier in the sleep cycle, you may also notice your best friend’s mouth hang open. In this state, also called “slow wave sleep,” all of your dog’s muscles relax. Their breathing slows, heart rate drops, and body temperature decreases slightly.

Since the jaws are slack, your dog might expose some teeth without actively grimacing.

While a dangling tongue or visible teeth might look silly or concerning, it’s perfectly normal dog behavior in the deep sleep phase. According to the AKC, you should only worry if your dog is struggling to breathe or excessively panting during sleep.

Opening their mouth allows for more effective heat regulation.

Of course, each pup has their own quirky sleep style. While plenty of dogs snooze with mouths agape, others may sleep more quietly with closed mouths. As long as your canine friend seems comfortable, content, and able to wake up readily, their sleep mouth position isn’t something to stress about!

Open Mouth While Awake Needs Evaluation

Dogs that sleep with their mouths open is often normal, but if they keep their mouths agape while awake, it could signify an underlying issue that requires veterinary evaluation. There are a few concerning reasons why a dog may pant or have their mouth open repeatedly without reason while conscious.

Could Indicate Heat Stroke, Pain or Anxiety

Excessive panting without physical exertion or hot ambient temperatures can be a red flag for heat stroke, pain, respiratory distress, or anxiety. Dogs pant to cool down, but pavement panting merits attention to rule out illness.

Labored, quick breathing with salivation, lethargy or restlessness hints heat stress, heart issues, nausea, or distress.

Panting Without Reason Sign of Distress

While dog mouths hang open to regulate body temperature, random fits of heavy breathing when relaxed flags potential problems. Unexplained panting episodes point to discomfort or internal turmoil, rather than mere overheating. Persistent wide-mouthed, rapid panting signifies:

• Cardiovascular abnormalities like heart murmurs
• Nausea, gastrointestinal, kidney or bladder disorders
• Acute stress or anxiety reactions
• Respiratory infections, kennel cough, pneumonia
• Anemia, blood cell abnormalities, bleeding issues

Other Symptoms to Watch For

Alongside inappropriate panting, look for supplementary signs of illness like:

• Lack of energy, lethargy, weakness
• Loss of appetite, dehydration
• Blue-tinged gums, tongue, eyelids
• Trembling, unsteadiness, disorientation
• Whining, agitation, clingy behavior

If labored breathing accompanies the above, promptly consult your veterinarian, as it may indicate oxygen deprivation, toxicity, injury or shock. Timely evaluation and treatment vastly improve outcomes.

While occasional air panting is normal dog behavior, excessive or odd breathing habits in already anxious pups warrants attention. If open-mouthed, distressed respiration tracks with other red flags, veterinary assessment helps determine any root physical or mental causes requiring relief or intervention through medication, rest, training or environmental changes.

Conclusion

While an open mouth is normal during a dog’s sleep, an extended open mouth while awake may indicate a medical issue needing veterinary attention. Understanding why dogs sleep the way they do can help you determine when their sleeping position is cause for concern.