Sleeping while flying overseas in an airplane isn’t exactly an amazing physical feat.
But sleeping while physically flying over an ocean?
Frigate birds do it.
Because brains!
Hey frequent fliers, Trace with you on DNews today.
Frigate birds have an impressive six-foot wingspan but their feathers aren’t waterproof
so they can’t rest on water, and yet they spend most of their lives at sea.
The exception is when they breed; they do that on land.
So if they can't land on water, and only come to land to breed…
how does this non-waterproof bird stay aloft over the ocean for weeks at a time?
It all comes down to their brains!
Most of us probably think of birds as flying around during the day and resting at night
like we do.
But frigate birds?
Uh-uh.
Earlier this year, a team from the Max Planck Institute for Ornithology in Germany tracked
the birds’ brain activity by fitting them with small devices able to measure electroencephalographic
(or EEG's / brainwaves) changes, including slow wave sleep and rapid eye movement sleep.
Data was gathered over 10 days while the birds flew more than 3,000km, and it revealed amazing
behaviour.
During the day the birds stayed awake, looking for fish or other birds to harass and steal
food from; they’re kinda jerks, but when you can’t land on water that's kinda how
you gotta live.
Then, at night, their brains did something super neat.
Frigate birds, like humans, have one brain divided into two hemispheres, but it turns
out frigates can shut down and rest only one hemisphere at a time, engaging it in short-term
stages of slow-wave sleep.
In other words, they sleep with one eye open -- while flying.
The birds typically circle upward on air currents in the direction of their open eye, which
is the one connected to the awake hemisphere.
The researchers think they do this to watch where they’re going and so they don’t
run into other birds.
Incredible as this is, frigates are not the only animal that sleeps with half its brain
awake at a time.
It’s an unusual sleep pattern called "unihemispheric slow-wave sleep."
Behaviourally, sleep is a period of rest in a species-specific posture.
Physiologically, it’s a state characterised by specific eye movements, muscle tonation,
and cortical rhythms.
In unihemispheric slow-wave sleep, only half of the cerebral cortex, the gray matter that
covers both hemispheres of the brain, displays the characteristic patterns of sleep, while
the other half shows neural activity of a waking state.
During this time the brain can’t get into full REM sleep; it can only fall into shallower,
slow-wave oscillation sleep.
Unihemispheric slow-wave sleep is how dolphins can rest without drowning or being killed.
A dolphin will shut down one hemisphere of its brain, leaving the other half of the brain
to monitor breathing function and keeping that eye open to monitor its environment (the
left eye will be closed when the right half of the brain sleeps, and vice versa).
It’s also something a lot of birds do, like mallard ducks -- keeping one eye open to watch
for predators while the rest.
So this method of getting some shut-eye isn’t exactly unheard of.
But in the study of frigate birds, the researchers found something even more amazing.
Apparently, frigate birds also occasionally shut down both hemispheres of their brain
at once and somehow don’t drop out of the sky like a hot rock.
They don’t do this for long; only a few seconds at a time, and all told, between the
half-brain sleep and occasional full-brain sleep, they only get about 42 minutes of shut
eye a day when they’re at sea.
Humans prefer to rest the whole brain at once, but amazingly in certain situations, we can
also do it a hemisphere at a time too.
In humans, unihemispheric slow-wave sleep is associated with the “first night effect,”
also known as your inability to get a good night’s sleep in a new location.
It's not a full separation between brain hemispheres; rather, it’s described as an asymmetry.
One hemisphere is more active and vigilant, monitoring the environment for unfamiliar
sounds in the new surroundings.
So next time you have a bad night in a new environment like a hotel or a new apartment,
think of how cool it is that your brain is tapping into the same evolutionary advantage
that birds and dolphins use.
Even though you’ll be too tired to be amazed.
Maybe.
So have you guys experienced this “first night effect”?
And speaking of weird ways of sleeping in the air, what about insects?
Do insects sleep?
Julian has the answer in this video right here.
Have you guys experienced this first night effect?
Let us know in the comments, make sure subscribe to you get more DNews and thanks for watching.