Researchers report December 22 in the journal Current Biology 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 more reindeer ruminate, the less additional non-REM sleep they need,” says first author and neuroscientist Melanie Furrer of the University of Zurich. “We think it’s very important that they are able to save time and cover their sleep and digestive needs simultaneously, especially during the summer months.”
Light-dark cycles are absent in the Arctic during winter and summer, and previous studies showed that Arctic-dwelling reindeer don’t display circadian behavioral 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. However, whether these seasonal differences also impacted how much—and how well—reindeer sleep was unknown.
To investigate the influence of seasonal light-dark cycles on reindeer sleep patterns, the researchers performed non-invasive electroencephalography (EEG) on Eurasian tundra reindeer (Rangifer tarandus tarandus) in Tromsø, Norway (69°N), during the autumn equinox, summer solstice, and winter solstice.
The reindeer, who were all adult females, were part of a captive herd at UiT, The Arctic University of Norway in Tromsø, and the experiments were conducted in indoor stables with controlled lighting, unlimited food, and constant temperature.
2023-12-23 08:00:04
Link from phys.org rnrn