Though Closely Related, Wolves and Dogs Sleep Differently

Researchers cuddled them to sleep to find out.

european wolf (Canis lupus lupus) sleeps in winter
Christian Heinrich / Getty Images

Imagine trying to sleep in new surroundings. You might toss and turn because of unfamiliar noises and a different environment.

Dogs are no different. They are much more comfortable and their sleep patterns change when they are at home versus in a strange place.

Curious about how being in a protected situation affects sleep, researchers in Hungary set out to see if the same was true for wolves. They found some striking differences.

“Dogs have become an important model animal in non-invasive comparative and translational cognitive neuroscience, including sleep research,” study author Vivien Reicher, a Ph.D. student at the Ethology Department of Eötvös Loránd University, Hungary, tells Treehugger.

“Considering dogs’ unique, shared evolutionary history and social environment with humans, comparing their sleep characteristics to that of wolves—the dog’s closest wild relative—offers a unique opportunity to better understand the effects of domestication and cohabitation with humans on sleep phenotypes and physiology.” 

Because sleep is affected by many factors, including physiological needs and evolutionary history, it may have different characteristics in different species, the researchers explain.

“Studying the sleep of different animal species helps us gain a better understanding of the core and more species-specific functions of sleep and the factors affecting them,” Reicher says.

Studying Sleep Differences

For their study, researchers took sleep measurements on both 20 family puppies and dogs and seven hand-raised wolves. Before the research, they first expended some energy by taking them for a long walk or having them play with their owners or handlers.

During measurements, the dogs were with their owners and the wolves were with their handlers, all with an experimenter in the room. The animals were given a chance to explore their new surroundings, then they were stroked and cuddled by their people until they fell asleep.

While the animals were starting to doze off, the experimenter attached electrodes to their heads for the measurement. If they woke up, they were calmed and snuggled back to sleep.

Researchers found interesting differences between the sleep characteristics of dogs and wolves. Dogs and wolves appeared to spend a similar amount of time being drowsy. But one main difference was that wolves spent more time in rapid eye movement (REM) sleep than dogs.

“Which is an intriguing result, since the amount of REM sleep has been linked to various different effects (and species) including neurodevelopment, stress, domestication, but also memory consolidation and relative brain mass,” says Reicher.

The findings were published in the journal Scientific Reports.

Unfamiliar Places

Unfamiliar surroundings have a different impact on humans versus dogs, researchers suggest.

“When we humans spend the night in a new, unfamiliar environment, we tend to feel unsafe and pay more attention to our external environment,” Reicher says. 

She says when people spend the night for the first time in a sleep laboratory, they take longer to fall asleep, they sleep less overall, and spend less time in REM sleep compared to someone who is sleeping in the lab for a second time.

Researchers found similar but slightly different results for dogs.

Dogs sleeping at home enter REM sleep more quickly than dogs sleeping in an unfamiliar place, like a friend’s house or the sleep lab. But if a dog was used to sleeping in other places, their sleep patterns were different, too.

“Dogs that often sleep away from home (e.g. at the workplace of the owner, coffee house) entered non-REM (NREM) and REM sleep stages earlier on their first sleeping occasion at our lab than dogs that only rarely sleep away from home,” Reicher says.

“This result suggests that dogs that are more accustomed to regularly visiting new locations and places with their owners show a decreased reaction to a novel sleeping location than dogs that are only used to sleeping in their home environment.”

Next Steps

Obviously, the wolf part of the study was easier because the animals were hand-raised and used to being around people.

“Wolves that are not used to the presence and proximity of people are generally very anxious and agitated if approached by humans, let alone are physically handled by them,” Reicher says. “Hand-raising and the early socialization of wolves are essential in being able to conduct such research gently with relaxed, calm and cooperative animals.”

Researchers believe this is the first study to examine the sleep patterns of wolves using non-invasive techniques.

They point out that their findings are only preliminary due to factors such as small sample size and limited age distribution, so they aren’t able to develop scientific conclusions.

However, says Reicher, the results are still fascinating and important.

“We consider our study as a first step in forming the basis of an international, multi-site collection of similar samples using our reliable, easily applicable, non-invasive methodology in different labs, collecting high-quality data that allows for generalizable scientific conclusions.”

View Article Sources
  1. study author Vivien Reicher, a Ph.D. student at the Ethology Department of Eötvös Loránd University, Hungary

  2. Reicher, Vivien, et al. "Non-Invasive Sleep EEG Measurement In Hand Raised Wolves." Scientific Reports, vol. 12, no. 1, 2022, doi:10.1038/s41598-022-13643-x