Researchers have discovered that the more time reindeer spend ruminating, the less time they spend in non-rapid eye movement (non-REM) sleep. EEG recordings revealed that reindeer’s brainwaves during rumination resemble the brain waves present during non-REM sleep, and these brainwave patterns suggest that the reindeer are more “rested” after ruminating. The researchers speculate that this multitasking might help reindeer get enough sleep during the summer months, when food is abundant and reindeer feed almost 24/7. The results were published on December 22 in the journal Current Biology.
Light-dark cycles are absent in the Arctic during winter and summer, and previous studies showed that Arctic-dwelling reindeer don’t display circadian behavioural rhythms during these seasons, though they tend to be more active during the daytime during the spring and autumn equinox, when light-dark cycles are present.
They found that reindeer slept approximately the same amount during winter, summer, and autumn, despite the fact that they were much more active during the summer. This is in contrast to other species who change the amount they sleep in response to environmental conditions. On average, the reindeer spent 5.4 hours in non-REM sleep, 0.9 hours in REM sleep, and 2.9 hours ruminating during a given 24-hour period, regardless of season.
