Ask the Vet
Dr. Brianne Hagerty, Avery and Bjorn
Do animals dream? The short answer is yes, in fact most vertebrates DO dream on a regular basis. I can only assume Avery, my Whippet, is dreaming of rabbits. I image him visualizing them weaving in and out of the stone fences crisscrossing the green slopes of the Pentland Hills, when he begins to excitedly yip and run in his dreams. In fact, I am sure that he dreams often of his finest rabbit chasing adventure during our hill walks:
This chase involved me quickly calling, in vain, to catch Avery’s attention before he spied the ears of a rabbit peeking over the edge of a gully. Too late, Avery already at the end of his leash, was off to the chase and over the edge of the bank. All that was left to be seen was the disappearing white tail of the rabbit. My slippery shoes on dried grass proved no match for his quick pull of enthusiasm and I hit the ground with a thud. All 12 kg of dog, leash now in tow, and a frightened rabbit ended my walk with a growing bruise. I have no doubt he dreams of this day often.
Dream sleep or Rapid Eye Movement Sleep (REM) is found in most vertebrates. This type of sleep is alternated with periods of non-REM sleep or slow wave sleep (SWS). Although we are asleep during SWS, with quiet mental processes, we maintain a level of muscle tone and are easily woken. Our pets may appear still, with eyes closed but seem to still notice every movement or sound. As we sink deeper into sleep, rapid eye movements occur and brain waves become faster and irregular as we enter REM. We may notice our pet’s eyes darting about rapidly beneath his or her eyelids. At this stage, complete with twitching muscles, soft whines and running paws, dreams are thought to occur. Vivid, sometimes illogical periods of dreaming are only seen in REM sleep for vertebrates and we begin to wonder what rabbit our four legged friend is after or what mouse is scurrying away just out of reach.
Although we will never read our dog’s “dream journal” or hear our cat’s account of their dreams upon waking, we can speculate. It is thought that based on the physiological similarities in sleep patterns and vertebrate’s ability to “think”; dreams are likely composed of things which occur during their waking hours.
Age is thought to play a factor in the length and frequency of dreams, and it is believed that puppies experience more dreams, as they must also process and encounter many new experiences, daily. Size is a second influencing factor, which is thought to dictate REM patterns. Research by Stanley Coren, a psychology professor and neuropsychological researcher at the University of British Colombia, illustrated that frequency of dreams may be related to an animal’s body size. An example of this showed that a small breed dog would have frequent dreams occurring every ten minutes, but only lasting less than a minute in duration. This contrasted a large breed dog, who was noted to dream only once every 60-90 minutes, however dreams would last five to ten times longer. It is speculated that this may relate to the amount of time spent sleeping; large dogs, on average, sleep for longer periods of time per day.
To gain insight into dreams, we looked at our small fuzzy counterparts. Sleeping rats were used to help prove the assumption that other vertebrates dream about events occurring during a waking state. Matthew Wilson and Kenway Louie of the Massachusetts Institute of Technology conducted a study comparing the brain activity of rats while running a maze and latter while sleeping. During the period of time the rat was placed in the maze, electrical recordings were taken from its hippocampus (the area of the brain associated with formation of memory and storage). A distinct pattern was noted depending on what the rat was doing, such as learning a maze. These distinctive and repeatable patterns were later identified during the rat’s period of dream sleep. This indicated that the rat was indeed “dreaming” of the maze it had previously explored while awake. Even more astonishing was the fact that the wave patterns could depict which part of the maze the rat was dreaming about!
I’ve often looked into the mischievous big brown eyes of Bjorn and wondered exactly what he wants, while he demandingly pushes my arm with his nose and whines impatiently. He’s had breakfast, he’s been on a run and has preformed his businesses, so now what? Unfortunately, in both their sleeping and waking hours, we rarely get to learn exactly what they are thinking. Therefore, at this point in time we can’t discern if our pets suffer from nightmares. However, a recent research study looking at the effect of emotional experiences on the pattern of canine sleep was conducted at the Hungarian Academy of Sciences in Budapest, Hungary. Anna Kis, and her colleagues looked at 16 dogs that experienced both a positive experience (playing a game of fetch or tug of war and affectionate petting) and a negative experience (being left by the owner in an empty room in which a stranger then approached and stared in a stalking and looming matter) occurring several days apart.
The dream behaviour of the dogs, based on their brain’s electrical activity, was different depending on which experience the dogs faced during the day; dogs who had a negative experience spent more time in REM sleep ( “dreaming”) than dogs who had a positive experience. Perhaps this suggests that they are actively “replaying” their concerns and attempting to resolve issues, almost like a “bad dream”.
I think we often take for granted the complexity of our furry companions’ thoughts and emotions, in both their waking and sleep states. What do they really have to tell us? Science continues to inch us closer to a better understanding, however it often remains a mystery.