Reindeer enters a state of non-REM sleep while eating.

The results of a study on reindeer sleep revealed that during

Reindeer Sleep and Eat Simultaneously, Saving Precious Time in the Short Arctic Summer | Science| Smithsonian Magazine
https://www.smithsonianmag.com/science-nature/reindeer-sleep-and-eat-simultaneously-saving-precious-time-in-the-short-arctic-summer-180983495/

Melanie Farrar, a neuroscientist at the Children's Research Center at the University of Zurich Children's Hospital, and her colleagues conducted research on reindeer sleep using reindeer brainwave data.

The research team spent four days in a facility at the University of Tromsø in Norway, recreating environments similar to the winter solstice (pitch darkness), summer solstice (midnight sun), and autumnal equinox that they would experience in the wild. I received it and collected brain wave data.

Most living things have an internal clock (circadian rhythm) that adjusts when they are exposed to morning light or eat food. However, it turns out that reindeer have almost no biological clock and follow environmental light conditions. Farrar and his colleagues predicted that, like the length of the night, sleep time would be shorter in the summer and longer in the winter, but in reality, there was no significant difference in sleep time between summer and winter.

Instead, reindeer were found to be able to enter a sleep state while ruminating, in order to get enough sleep during the short summer nights.

According to research, reindeer's brain waves during rumination were similar to those during non-REM sleep. In fact, while ruminating, the reindeer were less attentive to their surroundings than when they were awake, and their reactions were similar to those when they were asleep.

Vladislav Vyazovsky, a sleep physiologist at the University of Oxford who was not involved in the study, said: ``Reindeer may be ruminating to switch their brains into meditation mode and get the meditative effect. That's really cool.'' I think so.”