How does hibernation work? - Sheena Lee Faherty
Onboard the spacecraft,
the astronauts preset the timer,
enclose themselves in capsules,
and fall into a deep hibernation
that’ll carry them several
hundred years into the future.
This is a familiar scene
in many sci-fi films,
but could humans ever actually
hibernate in real life?
Researchers interested in this question
turn to the animal kingdom,
where hibernation is commonplace,
occurring in over 200 species
that we know of.
Take the Arctic ground squirrel.
Native to the North American tundra
and northern Russia,
this animal burrows
beneath the permafrost
and slips into a state
of suspended animation,
its body temperature plummeting
to a frigid -2.9 degrees Celsius.
Others, like the female black bear,
can multitask,
giving birth and lactating while they’re
hibernating through the winter.
The fat-tailed dwarf lemur prepares
for its long dormancy
by gorging on food and storing the
majority of its fat reserves in its tail,
doubling its body weight.
After hibernation, it emerges looking
as svelte as ever.
So why do these animals
go to such extremes?
Hibernation is a necessity,
a survival tactic for making it
through the harsh winter months
when dwindling food
and water reserves threaten survival.
For many years, experts believed
hibernation happened
only in arctic and temperate environments.
But more recently, they’ve discovered
animals hibernating
even in arid deserts
and tropical rainforests.
As hibernation kicks in,
animals’ heartbeats usually slow to
about 1 to 3% of their original speed,
like the dwarf lemur’s,
which drops from its usual
roughly 180 beats per minute
to just around four.
Breathing also declines dramatically
to just one breath every 10 to 21 minutes
in the lemur’s case.
And black bears, like most hibernators,
don’t urinate
or defecate the entire hibernation season.
Hibernating animals appear to stay alive
by having just enough blood
and oxygen moving around their bodies.
And scans of hibernating animals
reveal that their brain activity
has just about flat-lined.
But hibernation isn’t a long winter’s nap.
As far as researchers know,
in lemurs and
ground squirrels anyway,
the animals aren’t even
sleeping for most of it.
Hibernation is actually made up of regular
bouts of reduced metabolic rate
and body temperature known as torpor.
Animals can be in torpor
for a few days to five weeks,
after which they resume normal
metabolic rate and body temperature
for about 24 hours,
before going back into torpor again.
The phenomenon is known
as an interbout arousal,
and why it occurs is still a mystery.
The behaviors inherent in hibernation,
like going five weeks without sleep,
or dropping to
near-freezing body temperatures
would be potentially fatal
to non-hibernating species like us.
To find out how hibernators
are able to do this,
researchers turned their attention
to those animal’s genomes.
So far, they’ve discovered that
hibernation is controlled by genes
that turn off and on in
unique patterns throughout the year,
fine-tuning the hibernator’s physiology
and behavior.
For example, ground squirrel, bear
and dwarf lemur studies
have revealed that these
animals are able to turn on the genes
that control fat metabolism
precisely when they need to use
their fat stores
as fuel to survive
long periods of fasting.
And the genes in question
are present in all mammals,
which means that researchers could
study hibernating mammals
to see how their unique control
of physiology might help humans.
Understanding how hibernators deal
with reduced blood flow
could lead to better treatments
for protecting the brain during a stroke.
Figuring out how these animals avoid
muscle deterioration
might improve the lives
of bedridden patients.
And studying how hibernating animals
control their weight with ease
could illuminate the relationship between
metabolism and weight gain in humans.
And yes, more research in this area
might someday make
human hibernation a real possibility.
Imagine our surprise if the key to
intergalactic travel
turns out to be ground squirrels,
black bears, and dwarf lemurs.
