Identification

• Dogs dream during only one phase of sleep, the REM sleep cycle. According to "Temporal Characteristics of Sleep in Dogs," a study published in the U.S. National Library of Medicine, dogs spend 20 percent of their time sleeping in REM with each cycle lasting roughly 30 minutes.
  
  

Theories/Speculation

• Animal dreams have not been well studied until recently. According to "How Dogs Think," by Stanley Coren, research studies now indicate that dogs dream similarly to humans. Owners have long assumed their dogs dream about hunting and other typical activities, a theory supported by dog behavior during sleep.
  
  

Behaviors

• Dogs cry, whimper, whine and even bark when dreaming. Observe your sleeping dog and you may see running, eating, ear twitching and more, all of which is normal behavior for sleeping dogs.
  
  

Additional Considerations

• Dogs also cry during the night when not sleeping, usually out of loneliness or a need to go outside. Some puppies miss the warmth and companionship of the litter and cry for this reason. Environmental reasons include uncomfortable sleeping arrangements, fear and temperatures that are either too hot or too cold.
  
  

Solution

• Leave your dog alone if he cries while sleeping. Startling your dog by waking him can cause him to bite in fear. If your dog cries at night when he is not asleep, determine the underlying issue and correct it.