In recent years, there has been an increased scientific interest in investigating canine sleep. Since dogs are a domesticated species adapted to the human environment, better understanding their sleeping patterns can shed more light on human sleep too, which could have been evolutionarily shaped by living in protected environments. Thus, similar changes might be expected in the sleeping patterns of other species adapted to such environments. For instance, dogs appear to sleep more superficially in unfamiliar environments, just as humans do.
Now, a team of researchers from Eötvös Loránd University (ELTE) in Hungary has measured for the first time the sleeping patterns of the dog’s wild counterpart, the wolf. In order to better understand the effects of domestication and cohabitation with humans on sleep physiology and phenotypes, comparing dogs to wolves offers a unique opportunity.
“Although dog-wolf comparative studies have already been conducted in several areas of research, including behavioral and genetic studies, the neural processes of wolves remain a largely unexplored field,” said study co-author Anna Bálint, a comparative ethologist at ELTE. “We measured the sleep EEG of seven hand raised, extensively socialized wolves, using the same methodology as has been applied in family dogs. We successfully measured all sleep stages (drowsiness, deep sleep, and REM) that were previously observed in dogs as well.”
During the experiments, the wolves have been surrounded by familiar people who petted and caressed them until they calmed down, became drowsy, and eventually fell asleep. Whenever they became aroused again, the caretaker and experimenter calmed the wolves by cuddling them until they fell back to sleep.
“While young dogs and wolves showed a pretty similar distribution of sleep stages, the time spent in REM seemed to be less in dogs than in wolves, and this difference is even more apparent in the senior animals,” reported study lead author Vivien Reicher, a doctoral student in Ethology at ELTE. “This finding is especially intriguing since the amount of REM sleep has been linked to various different effects including neurodevelopment, stress, domestication, but also memory consolidation.”
According to study senior author Márta Gácsi, an expert in Comparative Ethology at ELTE, although the sample size was rather low and the age distribution of the wolves was too skewed to draw comparative conclusions, these experiments can be considered important first steps in collecting an adequate amount of data to properly describe the wolf’s sleeping patterns.
“Thus, we suggest that using our reliable, easily applicable methodology in different labs may form the basis of an international, multi-site collection of similar samples, allowing for generalizable scientific conclusions,” she concluded.
The study is published in the journal Nature Scientific Reports.