It is not uncommon for first-time dog owners to grow concerned about their dog's sleeping patterns. Indeed, watching a dog trembling while sleeping may appear like a worrisome sign of something not right: perhaps a seizure or some other worrisome health condition. Other times, novice dog owners may mistakenly believe their dog is trembling during its sleep because he is cold and therefore may grab their pet a blanket. However, in most cases, trembling during sleep is a normal occurrence, something that takes place during specific stages of sleep.
Just as humans, dogs undergo different stages of sleep. When the dog closes its eyes and falls asleep, he is undergoing the first stage, known as slow wave sleep. During this stage the brain waves are low and the dog appears calm and relaxed. The next stage is the rapid eye movement (REM) stage where brain waves are rapid and uneven. This is the stage where dogs very likely dream and begin to twitch, tremble, breath rapidly and even vocalise.
It is estimated that adult dogs spend about 10 per cent to 12 per cent of their sleeping in the REM stage, according to Dr. Nicholas Dodman. Compared to adult dogs, puppies are known to spend much more time in the REM stage, therefore they are often seen trembling a lot during their sleep. This may be attributed to the fact that they as they grow they are dealing with huge quantities of newly acquired data.
It is important to point out that very small puppies are commonly seen twitching and jerking during this particular stage in their lives. This deep form of sleep known as ''activated sleep'' is the main part of a puppy's sleep until four weeks old and its purpose is to strengthen those muscles necessary to allow the puppy to stand, according to William Fortney, DVM. For this reason it is important to allow puppies to get a lot of sleep.
While a dog trembling while sleeping is most likely going through a REM phase, it is important to report to a veterinarian if this is a new behaviour and, most of all, if the trembling continues while awake. Dogs in pain, with a high temperature or simply nervous may be seen trembling when laying down and trying to fall sleep. Other common causes of trembling are ingestion of toxic substances, allergic reactions, hypoglycaemia, electrolyte imbalances, shock and minor seizures, according to Eric Barchas, D.V.M.
While trembling is more likely than not a sign that the dog is in its REM phase, it is difficult to prove that dogs are just as capable as humans of dreaming. Being an animal spared the gift of voice, only suppositions can be truly made. However, if dogs in reality do dream, their trembling and body movements appear to suggest they are hunting. Simply watching the dog's ears pulled back, neck extended, rapid breathing and its feet twitching and churning, it can easily be noted that it mimics a dog running after a rabbit, according to Thinkquest.org.