A recent sleep study has found an astonishing brain adaptation north of the Arctic Circle. Recording the brain waves of reindeer for the first time, a team of researchers from Switzerland and Norway have uncovered a fascinating insight into the multi-tasking brains of these ruminants.
Image Credit: Frank Meissner
Image Credit: Gabriela Wagner
Reindeer have an evolutionary strategy that allows them to thrive in the face of drastic changes in daylight and food supplies. Like other deer, reindeer ruminate their food—hiccupping small amounts of hard-to-digest plants from the stomach for repetitive chewing. During rumination, deer appear relaxed, almost as if in a "trance-like state" (via Wildlife Online).
The researchers discovered that rumination is more than just a dietary necessity for reindeer; it's a chance to switch the brain into slow-wave sleep mode.
Conducting their study during the days surrounding the fall equinox and Arctic solstices, the scientists used electroencephalography (EEG) to record the brain activity of four female reindeer. They identified specific states such as wakefulness, rapid eye movement (REM) sleep, non-REM (NREM) sleep, and rumination.
It turns out that during rumination, reindeer's brain waves closely resemble those observed during NREM sleep. This chewing/sleep state appears to be restorative. Melanie Furrer, the first author from the University of Zurich, explains: "The more reindeer ruminate, the less additional non-REM sleep they need" (via Cell Press).
"It's crucial for reindeer to spend enough time ruminating during the summer in order to gain weight in anticipation of winter," Furrer notes. The restful, slow-wave activity of their brain during rumination allows reindeer to capitalize on the abundance of summertime greens without sacrificing their beauty sleep.
Image Credit: Current Biology Furrer et al., 2023
"This is the first study to show that phases of rumination not only share EEG characteristics with NREM sleep but that they also contribute to the dissipation of sleep pressure similarly to NREM sleep," the researchers conclude.
These findings highlight a sophisticated adaptation of the brain to optimize behavior and ensure survival in the extremes of the Arctic landscape.
Sources: Wildlife Online, Current Biology
