In the enchanting realm of the Arctic, reindeer gracefully roam and cavort through the meadows, showcasing a mesmerizing phenomenon that has perplexed scientists for centuries. These magnificent creatures have been unearthed to possess the remarkable ability to slip into a sleep-like state while savouring their meals, enabling them to make the most of their feasting time amidst the bountiful Arctic summers.
According to a research study recently published in Current Biology, reindeer exhibit an extraordinary knack for putting their brains into a sleep-like mode while engaging in the process of rumination. Melanie Furrer, a neuroscientist at the University of Zurich and the study’s lead author, elaborates on the reindeer’s unique capacity to fulfill both their digestive and sleep needs simultaneously, establishing them as highly efficient beings in the animal kingdom.
Much like cows, reindeer boast four stomach chambers, using the first chamber to store grass for later regurgitation and chewing. This rumination process allows reindeer to meticulously process their food and absorb all the vital nutrients necessary to thrive in the Arctic landscape.
The study involved capturing electroencephalogram (EEG) recordings of captive Eurasian tundra reindeer in Tromsø, Norway, across different seasons. The researchers noticed that as the reindeer ruminated, their brains displayed an increase in slow waves and rhythmic bursts of activity, resembling patterns linked with non-REM sleep. Despite having their eyes open, the ruminating reindeer displayed sleep-like behaviours by sitting or standing quietly, and reacting less to surrounding noises.
Strikingly, the more time reindeer spent ruminating, the less actual sleep they seemed to require. When the researchers deliberately reduced the reindeer’s sleep time, they observed an escalation in slow-wave activity in the reindeer’s brains, indicating an intensification of sleep pressure. However, when engaged in rumination, their subsequent sleep showed less slow-wave activity compared to reindeer that did not ruminate. This led to the conclusion that reindeer can effectively ‘sleep’ during rumination, thus mitigating their need for deep sleep.
Melanie Furrer proposes that this remarkable adaptation is the reindeer’s response to the divergent Arctic seasons, where they encounter a surge in lush, grassy summers followed by a dearth of food during the snowy winters. By maximising their eating time in summer, reindeer are able to pack on weight for the harsh winter months when food availability is scant.
The study’s findings disrupt the prevailing belief that animals sleep less in summer and more in winter based on environmental conditions. Furrer asserts that reindeer consistently maintain their total sleep time throughout the year, underscoring the essential and tightly regulated nature of sleep in these captivating creatures.
This groundbreaking research has left experts in awe, casting a spotlight on the intricate connection between an animal’s sleeping patterns and its environment. Jerome Siegel, a neurobiologist at the University of California, Los Angeles, lauds the study as a valuable addition to the understanding of animal sleep, advocating for further exploration into how sleep-like brain activity during rumination influences the need for deep sleep in other animal species.
