The orangutans sleep the nap to recover the hours of sleep lost at night and restrict physiologically and cognitively. In fact, when the night dream is less, the greatest nap, according to a study published Wednesday in Current Biology.
“Move through the treetops, look for food, solve problems, manage social relationships … They are exhausting tasks that demand a great cognitive effort” and a repairing break.
So, “when an orangutan does not sleep enough, it does what any human would do: he gets into bed, he touches and a nap,” summarizes Alison Ashbury, first author of the study and researcher at the Max Planck Institute of Animal Behavior.
The objective of the research, carried out by the Max Planck Institute for Animal Behavior (MPI-AB) and by the University of Constance, in collaboration with scientists from the Nasional University in Indonesia, was to study the dream in our closest relatives to try to better understand the evolutionary functions and origins of the sleep.
“Why animals, from humans to primates, through spiders or jellyfish, evolved to spend much of their life in this vulnerable state of unconsciousness? If we want to answer this question we must get out of the laboratory,” explains the co -author Meg Cropofot, of the Max Planck Institute of Animal Behavior.
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14 years of research
For fourteen years, the authors gathered data from 53 adult orangutans at the Suaq Balimbing monitoring station, in the Tropical Indonesian jungle of Sumatra, and recorded 455 days and sleep nights of the orangutans.
In 41 % of the days observed, the orangutans slept at least one nap, with a total average duration of 76 minutes.
To sleep, the orangutans sleep in nests, some ‘beds’ that build in a few minutes with branches and leaves and that, except for rare exceptions, are individual. Only mothers share nest with their infants.
“From our point of view on the ground, we cannot usually see the orangutans in their nightlife, but we can hear them move and accommodate,” says Caroline Schuppli, main author of the study and group leader at the Max Planck. “In the end, everything remains in silence and still. And the opposite happens in the morning.”
It was that section of silence in the middle that the investigators called “period of sleep” and the one they used as an indicator of the sleep. They discovered that the dreams of the orangutans lasted, on average, almost 13 hours.
They also discovered that several factors were associated with shorter night sleep periods: sleep near other orangutans, colder night temperatures and longer daily displacements.
Repairing nap
To understand how the orangutans of sleep loss recover, the team analyzed how the duration of nap periods in relation to the rest of the previous night changed.
They found a clear compensatory effect: the seaps of the orangutans were longer the days after nights in which they had slept less and, when they slept their nap, they did it between 5 and 10 minutes for every hour less that they had slept last night.
“For people, even a short nap can have significant restorative effects. It is possible that these naps help the orangutans to restore physiologically and cognitively after a bad night of sleep, as with human beings,” says Crophoot.
For naps, the suag orangutans built new nests, which although they were simpler, were still stable and safe to sleep.
“Diurnal nests are less sophisticated, they have fewer comfort elements and are built faster than nightlife but, even so, when we see an orangutan resting in a daytime nest, we observe that their body is relaxed and their eyes closed. They really seem to be sleeping,” says Schuppli.
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Researchers believe that these findings may also be related to the cognition of orangutans, since the population of SUAQ is known for its use of tools and cultural complexity, traits that may require robust mechanisms to cushion sleep deprivation.
For Schuppli, the relatively high propensity of these orangutans to the use of diurnal nests for nap may be due to the fact that “either these high quality naps need to meet their cognitive demands, or their cognitive abilities may be due to the fact that high quality naps sleep in diurnal nests with such frequency.”
But this nap strategy can also be possible thanks to the SUAG ORANGUTANES SEMISSOLITARY LIFE STYLE.
With EFE information
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