

How do dolphins sleep without drowning? [video] - deepakjc
http://www.smithsonianmag.com/ist/?next=/videos/category/ask-smithsonian/ask-smithsonian-how-do-dolphins-sleep-witho/

======
deepakjc
Pretty surprising answer, they sleep half their brain at a time!

~~~
lutusp
Some migrating birds use this strategy also.

[http://en.wikipedia.org/wiki/Unihemispheric_slow-
wave_sleep](http://en.wikipedia.org/wiki/Unihemispheric_slow-wave_sleep)

~~~
yareally
If you venture to a local pond/lake and observe the mallards and black ducks,
some of them have one of their eyes open while sleeping because they can keep
half of their brain awake. I just happened to notice it while on a daily walk
and had to go look it up afterwards. Ducks also make outrageously loud quacks
when alarmed (sounding similar to a single person laughing too hard at an
unfunny joke). Made me jump more than once when walking after dark.

Not all of them will always sleep with one eye open, but at least a few in a
group will in order to keep watch from coyotes, birds of prey and stray cats
when they're not in the water.

------
mholt
Heads up: video with sound auto-plays.

Here's a direct link to bypass the advertisement:
[http://www.smithsonianmag.com/videos/category/ask-
smithsonia...](http://www.smithsonianmag.com/videos/category/ask-
smithsonian/ask-smithsonian-how-do-dolphins-sleep-witho/?no-ist)

------
lightblade
I wonder if human can be trained to do this. Certainly sounds like something
coming out of sci-fi or martial art movie.

~~~
lukeholder
I have heard of Cowboys sleeping with eyes open, but not sure if thats just a
old wives tale.

~~~
reitanqild
I know first hand someone who have driven several kilometres only to "wake up"
and not being able to explain. This is of course extremely dangerous and in
every case I know of it has ended with a damaged / wrecked car though luckily
no injuries or fatalities. (Back country roads, middle of the night etc).

What happened in at least one of these cases was dreaming with eyes open. From
what I hear that might not be to uncommon but here I'm back to old wives
tales.

~~~
dedward
There is a case to be made with these situations that you weren't actually
asleep.. you just didn't lay down memories for the period of time, because
nothing happened.

You feel like time is missing because you have no recollection of that time -
but that does not have to equate to you not being awake, or able to respond.

------
140am
Interesting - i know a few people who seem todo that throughout the day

------
heroku
wait a sec, do they sleep 8 hours total, or 8 hours per side. Because if they
sleep 8 hours that makes it only 4 hours.

------
lukasm
Giraffe sleeps in 10-15 min increments.

------
darklrd
Very interesting!

