[ELI5] Why can other species sleep with their heads up but we can’t?
In: Biology
REM sleep (at least for mammals, not a bird expert) still requires that the head be in contact with a hard surface for other animals due to the loss of muscle tone. Other animals make use of different sleep patterns so it’s easy to miss (REM sleep can be very short and broken up into several cycles).
Eg. horse REM sleep occurs in short periods (8-15 minutes frequently) in lateral recumbency, and their overall sleep for the day is broken up over several short sessions (often at night, but not always). If a horse is unable to lie down in lateral they cannot get REM sleep unless their head and body are supported in some other way (like a body sling with a cushioned head stand).
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