Your dog lies asleep at your feet, and suddenly his legs begin to twitch and run. Is he dreaming? Or are you dreaming to think such a thing? Wake up and smell the dog food! Of course he's dreaming. Why would you think otherwise?
Although no one really knows the true function of dreaming it does seem to be necessary for normal data processing and memory storage. Dogs think and they have memory. And their memory banks need period purging and reorganization during sleep just as ours do.
They experience Rapid Eye Movements (REM) under their closed eyelids while asleep, which indicate dreaming in humans. Younger dogs dream more than older ones although dogs dream all their life. Many dogs move their whiskers and lips, licking and chewing while dreaming. They paddle their feet like they're running or swimming. Some dogs, like yours, make little yips or howls. Others growl, whine, and wag their tails. Some dreams may frighten dogs because they wake up with a start.
When REM sleep is achieved they are at their most relaxed and are most difficult to waken. It is during this more profound physical sleep that their eyes begin to dart and the brain waves pick up pace. Humans awakened from this state report that they have been dreaming; dogs are probably dreaming too when they are in REM sleep, although no dog has ever told anyone about a dream he’s had.
Incidentally, adult dogs spend about 10 to 12 percent of their sleeping time in REM sleep. Puppies spend a much greater proportion of their sleep time in REM sleep, no doubt compacting huge quantities of newly acquired data. Veterinarians suggest not waking your dog when he's dreaming since dreaming is natural and normal. Dogs need to dream, just like humans.
And if you’ve ever wondered whether dogs that seem to be running during sleep are dreaming of catching rabbits or something similar, you can safely say they are.