Animal Sleep

Mon, Aug 31, 2009

Animal Sleep

Sleep is a naturally recurring state of relatively suspended sensory and motor activity in animals, characterized by total or partial unconsciousness and the nearly complete inactivity of voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and it is more easily reversible than hibernation or coma. It is observed in all mammals, including humans, all birds, and many reptiles, amphibians, and fish. In humans, other mammals, and a substantial majority of other animals that have been studied (such as some species of fish, birds, ants, and fruit flies), regular sleep is essential for survival.

The purposes and mechanisms of sleep are only partly clear and are the subject of intense research (Wikipedia).

Sleep in non-humans



Sleeping    Japanese   Macaques 

Sleeping Kitten


As you well know it is very difficult to establish sleep states in animals simply because they do not response to any question they asked. Well, they do not speak our languages. However, all of them sleep regularly or even longer then humans. It is also difficult to establish neurological sleep states. To define sleep states in animals we need to observe their behavior, movement during asleep, their body positions, and their responses to different stimulations. It has also been observed that sleep time in animals is quickly reversible, in comparison to hibernation or coma. It also has been studied that animals who have been exposed to sleep deprivation are trying to follow that by longer or deeper sleep.

  • Horses and other herbivorous ungulates can sleep while standing, however they need necessarily lie down for REM sleep for some short periods.
  • Giraffes only need to lie down for REM sleep for a few minutes at a time.
  • Bats sleep while they are hanging upside down
  • Reptiles generally begin brumation in late fall. Brumation is an example of dormancy in reptiles that is similar to hibernation. It differs from hibernation in the metabolic processes involved. They will often wake up to drink water and return to “sleep”
  • As study shows, some aquatic mammals and cirtain birds can sleep while one half of their brain is asleep and the other half is awake. This phenomenon is called unihemispheric slow-wave sleep.
  • Birds and mammals have cycles of non-REM and REM sleep (as described above for humans), though birds’ cycles are much shorter and they do not lose muscle tone (go limp) to the extent that most mammals do.
  • Many mammals sleep for a large proportion of each 24-hour period when they are very young.
  • Ducks and most birds also keep one eye open and one half of the brain awake at all times. This is called unilateral eye closure. This unusual sleeping technique allows these animals to stay alert to predators.
  • Killer whales and some dolphins do not sleep during the first month of life. Such differences may be explained by the ability of land-mammal newborns to be easily protected by parents while sleeping, while marine animals must, even while very young, be more continuously vigilant for predators. 
  • Brumation is an example of dormancy in reptiles that is similar to hibernation. It differs from hibernation in the metabolic processes involved
    Herbivore is an animal that is adapted to eat plants and not meat
    Ungulates (meaning roughly “being pawed” or “hoofed animal”) are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving
    Uni-hemispheric  slow-wave sleep (USWS) is sleep in which one half of an animal’s brain is at rest, while the other half remains alert. During USWS, only one eye is closed, allowing the animal to remain alert to activity in its environment. It has been observed in various 

How do animals and birds sleep? 





    Mallards sleep in a line



    Dolphins and other large sea mammals keep one eye open and one half of the brain awake at all times to maintain patial consciousness that is required for breathing and preventing them from possible threats






    Bats sleep upside down because their wings aren’t really strong enough to to take off  the ground. That is why they hanging in case they rapidly need to fly. In addition,  they need very litle efforts to hang.  

    Swainson’s Thrush

    Swainson’s Thrush, also called Olive-backed Thrush, is a medium-sized thrush that takes hundreds of naps during the day, ususally a few seconds in duration, even while flying. Migrating birds tends to adopt micro-naps.




    Common Poorwill

    Common Poorwill is unique because it is the only bird known to go into hibernation for extended periods of time (from weeks to months). It spends much of the winter time with no visible motion hiding within rocks.



    The giraffe has one of the shortest sleep requirements of any mammal, which is between 10 minutes to two hours with a 24-hour cycle period, averaging about 2 hours a day.




    Dwarf Lemur

    Fat-tailed Dwarf Lemur hibernates for seven months of the year hiding in a hollow part of a treeet. It is the first tropical primate in which hibernation has been observed for the first time. Lemurs do not regulat their body temperature while hibernating, only when they are awaken. If a tree hollow  is not well insulated, their body temperature fluctuates with outside temperature.


     Guinea Baboons

    Guinea Baboons sleep on its heels sitting pright on top of a tree. This helps them stay alert while asleep. Baboons have been also observed yawning to threaten their enemies.




    Hazel Dormouse

    One distinct characteristic of a dormouse is hibernation. It can hibernate six months out of the year, or even longer, providing the weather remains cool. Occasionally, they are waking up for brief periods of time to consume food they had previously stored. Hazel Dormouse can spend a lot of time sleeping by carefully balancing itself on the branch of a tree quite safely with the knowledge that any quiver of the twig will wake it up immediately. They spend most of their awakening hours among on trees seraching for food. They would rather make a long trip down on the ground instead of exposing themselves to imediate danger.


    Hibernation or ‘winter sleep’ and a ‘summer sleep’ by certain animals is a paramount. Frogs are the best example of hibernators phenomena known to people. Northern leopard frogs can spend the whole winter at the bottom the lake, far beneath the ice. They settle quietly on the lake bottom. Frogs’s bodies have some kind of natural chemical antifreeze preventing them from a very cold temperature. Some species can survive being solid frozen with no heart beat or breathing for weeks at a time.





    Albatrosses are known to sleep while flying with the speed of about 25mph. In addition, the Wandering Albatross has a wingspan of nearly 12 ft (3.7 m), the longest of any known bird.


    Watch Video: Animal Sleeping





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