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Reindeer are able to sleep and eat at the same time

In the world of animal behavior, reindeer have presented a fascinating new insight. Researchers from the University of Zurich, led by neuroscientist Melanie Furrer, have discovered a unique aspect of reindeer’s sleep and rumination patterns.

The findings suggest that rumination, a process in which reindeer re-chew partially digested food, serves as a mechanism for both rest and digestion, ensuring the reindeer efficiently utilize their sleep time.

Reindeer rumination linked to sleep

The study highlights a significant finding. The more reindeer ruminate, the less they require non-rapid eye movement (non-REM) sleep.

This conclusion was drawn from electroencephalography (EEG) recordings, which showed that brainwave patterns during rumination closely resemble those during non-REM sleep. This similarity suggests that rumination effectively provides rest, reducing the reindeer’s need for additional sleep.

“The more reindeer ruminate, the less additional non-REM sleep they need,” says first author and neuroscientist Melanie Furrer. “We think it’s very important that they are able to save time and cover their sleep and digestive needs at the same time, especially during the summer months.”

Reindeer’s seasonal sleep patterns

The researchers’ interest was in understanding how the unique Arctic light-dark cycles affect reindeer behavior, especially their sleep patterns.

Studies show that in Arctic regions, where light-dark cycles are absent in winter and summer, reindeer do not display typical circadian rhythms. However, they are more active during daylight in the spring and autumn equinox.

To explore this further, the team studied Eurasian tundra reindeer in Tromsø, Norway, during different seasonal transitions throughout the year. These reindeer, all adult females from a captive herd at The Arctic University of Norway, were observed under controlled conditions.

Remarkably, they slept approximately the same amount across seasons, despite increased activity in summer.

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

Rumination as a reindeer sleep substitute

One of these strategies is rumination, a process of re-chewing partially digested food. Similar to other ruminants, reindeer appear to use this process as a restorative substitute for sleep. The EEG readings during rumination showed increased slow-wave activity and sleep spindles, typical of non-REM sleep.

Reindeer, both sleeping and ruminating, exhibited similar behaviors, usually sitting or standing quietly during these states. They showed less reaction to disturbances like nearby reindeer moving.

Awake reindeer looked towards such movements 45% of the time, compared to 25% when ruminating, and only 5% during non-REM sleep.

The study also found that rumination could lower the reindeer’s need for sleep. After sleep deprivation, reindeer showed increased slow-wave activity, indicating a greater need for deep sleep. However, this need diminished with more rumination.

“This suggests that rumination reduces sleep pressure, which could benefit the reindeer because it means they don’t have to compromise on sleep recovery when they spend more time ruminating,” says Furrer.

This is especially important during the summer, because the more they eat, the more time the reindeer need to spend ruminating. “Rumination increases nutrient absorption, so it’s crucial for reindeer to spend enough time ruminating during the summer in order to gain weight in anticipation of winter,” says Furrer.

More reindeer sleep research needed

While the study provides novel insights, it also opens up avenues for further research. The team suggests comparing the effects of rumination during sleep and wakefulness and extending observations to more natural outdoor conditions.

Furrer also proposes examining sleep patterns in younger reindeer, given the higher sleep needs in younger mammals.

“Another thing we could add is to look at young reindeer,” says Furrer. “We know sleep need is much higher in young children and babies compared to adults, so it would be interesting to look at sleep in younger reindeer.”

In summary, this research enhances our understanding of reindeer biology and contributes to the broader knowledge of sleep and digestion interplay in animals. Understanding these unique patterns in reindeer can shed light on the adaptive mechanisms animals use to cope with extreme environments.

More about reindeer

As discussed above, reindeer, known for their remarkable adaptations to cold climates, have captivated people’s imagination for centuries. These hardy creatures, thriving in the harshest Arctic environments, are a symbol of winter folklore, yet also play a crucial role in the ecosystems they inhabit.

Remarkable Arctic survival features

Reindeer boast a set of unique physical traits that make them well-suited for cold climates. They have thick, double-layered coats that provide insulation against freezing temperatures.

Their fur traps air, which serves as an excellent insulator. Furthermore, their large, wide hooves act like natural snowshoes, helping them traverse snowy landscapes with ease.

During winter, the edges of their hooves harden to cut into ice and snow, providing better grip.

Behavioral traits

Reindeer are renowned for their long migratory journeys, traveling up to 1,200 miles, which is one of the longest migrations of any land mammal.

They move in large herds, a behavior that offers protection from predators and efficiency in finding food. Socially, reindeer display a hierarchical structure, with dominant individuals leading the herd.

Diet and nutrition

In the Arctic tundra, where vegetation is scarce, reindeer have adapted to survive on a limited diet. They primarily feed on lichens, known as reindeer moss, along with leaves, herbs, and grasses.

Their unique digestive system allows them to extract nutrients effectively from these limited resources.

Vital contributors to ecosystems

Reindeer play a vital role in their ecosystems. They act as seed dispersers, aiding in plant regeneration. Their grazing patterns also help to shape the landscape. Culturally, reindeer have been integral to indigenous peoples in the Arctic, providing a source of food, clothing, and transport.

Conservation and threats

Despite their adaptability, reindeer face threats from climate change and habitat loss. Warming temperatures and changing landscapes are impacting their traditional migratory routes and food sources.

Conservation efforts focus on preserving their habitats and understanding the impacts of environmental changes on their populations.

Reindeer, with their unique adaptations and significant ecological roles, are more than just a symbol of the holiday season. They are a testament to the resilience of wildlife in the face of harsh environmental challenges.

The full study was published in the journal Current Biology.


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