Rudolph and other reindeer have a gift for multitasking, study finds

Some people, as the phrase goes, are so bad at multitasking that they “can’t even walk and chew gum at the same time.”

The same cannot be said about reindeer, however, with a new study suggesting that Rudolph and his ilk can sleep and chew at the same time.

Specifically, researchers from Norway and Switzerland found that the brain waves seen in reindeer while ruminating—re-chewing partially digested food to help absorb more nutrients—often resemble those seen during non-REM sleep.

Non-REM, in which rapid eye movement (REM) is not shown, are stages of sleep in which the brain organizes memories, heals wounds and allows one to wake up feeling rested.

A herd of reindeer. A new study suggests that reindeer can sleep while rummining.
Gabriela Wagner

The team believes that reindeer can multitask in this way to get more rest in the summer months without having to sleep for long hours.

This can be essential for animals, which feed almost non-stop at this time of year in preparation for the long and food-scarce Arctic winter.

The study was conducted by neuroscientist Melanie Furrer of the University of Zurich and her colleagues.

“The more reindeer ruminate, the less additional non-REM sleep they need,” Furrer said in a statement. “We think it’s really important that they can save time and cover their sleep and digestive needs at the same time—especially in the summer months.”

At this time of year in the Arctic, the sun is always visible above the horizon. In contrast, in winter, the Arctic experiences permanent night.

In fact, previous studies have found that during these periods, in the absence of light-dark cycles, reindeer living in the Arctic do not show the usual rhythms of behavior that are more active during the day, as they do at other times of the year.

However, it was previously unclear whether these seasonal differences also had an effect on how much – and how well – the animals slept.

In the new study, the team measured the brain activity of four Eurasian tundra reindeer at three times: at the monsoon equinox, at the summer solstice, and at the winter solstice.

The animals, all adult females, belong to a captive herd kept at the University of Tromsø–The Arctic University in Norway.

All experiments were carried out in indoor stables, with the reindeer given access to unlimited food and kept under controlled lighting and constant temperature.

Although reindeer are more active during the summer, researchers have found that reindeer sleep the same amount during summer, fall and winter—meaning that their sleep needs are closely regulated by brain, and not around them.

This, the author of the paper Gabi Wagner of the Norwegian Institute of Bioeconomy Research in Oslo explains, is in contrast to various other species that change the amount they sleep in response to environmental conditions.

According to a 2018 study, he said Newsweek“The Arabian oryx sleeps almost twice as much in winter (6.7 hours) as in summer (3.8 hours).”

Other examples, he added, include fur seals, which inhibit REM sleep when forced to sleep in water; male pectoral sandpiper, which sleeps only one hour per day during the breeding season; and great frigatebirds, which sleep while flying, but count their duration when in the air.

On average, the team noted, the reindeer spent 5.4 hours in non-REM sleep and 0.9 hours in REM sleep per day, regardless of season—as well as roughly 2.9 hours ruminating.

“The fact that reindeer sleep the same amount during winter and summer means that they must have other strategies to cope with the limited sleep time during the Arctic summer,” said Furrer.

A close-up of a reindeer
A close-up shot of a reindeer’s face. To maximize the nutrients they get from their food, these animals re-chew the partially digested material.
Leo Rescia

When both were sleeping and ruminating, the team found that the reindeer showed similar behavioral patterns, tending to sit or stand quietly, and reacting less to disturbances than their neighbors who were sitting or standing up. .

In fact, the animals responded to such stimuli only 25 percent of the time when ruminating and 5 percent of the time during non-REM sleep, compared to 45 percent of the time when wide awake.

While humming, the animals were also found to often close their eyes, as they usually do while sleeping.

And when chewing food, readings of reindeer brain activity often appear similar to those seen in non-REM sleep—including an increase in so-called slow wave activity.

This activity, the researchers explained, indicates a build-up of “sleep pressure,” the unconscious biological drive for more and deeper sleep.

It’s not entirely clear whether the reindeer are fully asleep while rumining, or in a sleep-like state, Wagner says—but the former seems likely, based on their brain activity.

He added: “This is also consistent with recent studies in other ruminants such as sheep, using a more invasive technique – electrodes inserted into the brain.”

Researchers experimenting on reindeer
Researchers are shown with reindeer. In one part of the research, the team kept the animals awake for two hours at a time.
Current Biology Furrer et al.

Scientists have previously determined that other ruminant animals—sheep, goats, cows, and small mice—also produce sleep-like brain waves while chewing food, but it is unclear whether this process also serves as sleep. function.

To test this with reindeer, the team experimented by depriving the animals of sleep for two hours using a combination of food and attention, and measured their brain waves while sleeping before and after it. interference.

Brain scans revealed that the reindeer experienced slower wave activity after sleep deprivation, indicating a build-up of sleep pressure and suggesting that they had deeper sleep.

However, the more the reindeer were confused after being kept awake and before falling asleep, the less slow they were during the time when they were drowsy, the team found,

“This suggests that rumination can reduce sleep pressure, which benefits the reindeer because it means they don’t have to compromise on sound sleep if they spend more time exploring,” Furrer explained.

Reindeer may not sleep all the time when grooming, Wagner explained, because like us they may need the right conditions to drift, without noise, distraction, or fear.

“It’s very important for reindeer that they get enough undisturbed time to ruminate,” he said.

Oleg Lyamin, who was not involved in the current study, is a researcher at the University of California, Los Angeles who is conducting research on sleep in another ungulate, or “hoofed mammal”, the small mouse-deer.

A small mouse-deer
A picture of a small mouse-deer. Rumination during non-REM sleep has previously been documented in these deer which, like reindeer, are ungulate mammals.
Wirestock/iStock/Getty Images Plus

“Rumination during non-REM sleep has been recorded in domestic ungulates and in small mouse-deer,” he said. Newsweek. “From my position, it’s not unusual for reindeer to experience rumination during non-REM sleep.”

“The link between sleep and thinking is a big puzzle for researchers,” said animal behavior expert professor Katy Proudfoot at the Sir James Dunn Animal Welfare Center in Charlottetown, Canada. Newsweek.

The problem, he explained, is that “the process of ruminating—chewing, swallowing, regurgitating and re-chewing food—interferes with our ability to measure sleep using electrophysiology.”

Furrer and his colleagues neatly overcame this issue by filtering the data and testing the level of arousal during rumination, reaching the conclusion that reindeer tend to sleep during rumination, Professor Emma Ternman, an animal scientist from Nord University in Norway, said. Newsweek.

He added: “This is a solid piece of the puzzle in ruminant sleep research – the next step is to quantify sleep during sleep.”

Reindeer grazing in the summer
A picture of reindeer grazing. Animals must eat almost non-stop in the summer in preparation for the Arctic winter.
Gabriela Wagner

As reindeer appear to only enter a sleep-like state while ruminating at certain times, future studies should also compare the effect of different ruminating behaviors, the team said. .

Ideally, they added, the reindeer would be studied in more natural, outdoor settings.

However, this would likely require surgically implanted brain activity sensors, as opposed to the non-invasive, skin-attached electrodes used in the current study.

“We know that the need for sleep is much higher in young children and infants compared to adults,” Furrer said. “That’s why it’s interesting to watch young reindeer sleep.”

A pair of reindeer in the snow
A pair of reindeer in the snow. Arctic winters are long and food is scarce.
Frank Meissner

“We think that this research may spur more studies investigating sleep during rumination in reindeer and other ruminants,” Wagner said. “Furthermore, it shows how important it is that the reindeer have enough time for uninterrupted exploration, as it is important for digestion and sleep needs.

“Therefore, we hope that future research and political decisions on human activities in reindeer/caribou rangelands will consider that reindeer have sufficient time and space for undisturbed rest.”

Proudfoot concluded: “Understanding sleep in different wild and domesticated species can give us insight into how sleep develops, as well as help us better meet the needs of these animals when they are under in our care.”

The full findings of the study are published in the journal Current Biology.