All language subtitles for nature.s37e04.a.squirrels.guide.to.success.hdtv.x264-w4f[eztv]

♪♪

NARRATOR: Squirrels.

One of the smartest,
most adaptable,

most successful creatures
on the planet.

What are the secrets
of their winning ways?

There are squirrels that
can survive a deep freeze...

[ Squeaking ]

...communicate
in complex languages...

and outwit their greatest
enemies.

Now we'll explore their
incredible talents

by working with the experts.

FULL: Squirrels are one of
the most agile animals on Earth.

JACOBS: This is a really
special animal.

It's kind of a three-
dimensional, spatial genius.

NARRATOR: And see the world
through the eyes of an orphan,

as he develops the skills he
needs to get back to the wild.

It's time to meet these
high-flying, nut-loving,

quick-thinking creatures

and learn just what it takes
to be such a great success.

♪♪

♪♪

♪♪

NARRATOR: The squirrel family
is big and successful.

There are almost
three hundred different species.

They've mastered a huge
range of habitats,

from frozen Arctic tundra...

to baking deserts.

There are ground squirrels with
homes in tunnels and burrows...

♪♪

...tree squirrels living
the high life in the canopy...

...and even flying squirrels

that can glide effortlessly
through the treetops.

This adaptability has enabled
them to conquer the globe

and colonize almost
every continent on Earth.

♪♪

But one that is actually
becoming rare

is the iconic Eurasian
red squirrel.

This tree squirrel was once
widespread across Europe,

Northern Asia, and Siberia,

especially in
ancient conifer forests.

But in several countries,
their numbers have plummeted,

and they're under threat.

In the UK, 75%
of the remaining red squirrels

are found here in Scotland.

With the species in decline,

every single red squirrel
is precious.

And one has just been rushed in.

♪♪

McALLISTER: Look at you!

So small!

So this is a baby red squirrel.

It's the smallest red squirrel
I've ever seen.

It looks to be,
maybe about 5 days old.

He has no hair, eyes closed,
pretty much pinkie form.

[ Chuckles ]

NARRATOR: The tree holding
his nest was cut down.

He'll now be totally dependent
on his new surrogate mom,

Sheelagh McAllister,
the head of small mammals

at the National Wildlife
Rescue Centre of Scotland.

She and the Rescue Centre team

look after nearly
10,000 animals every year,

from foxes to otters.

McALLISTER: All right.
There you go.

NARRATOR: Sheelagh is
a specialist

in caring for red squirrels

and releasing them
into the wild.

But this one is the youngest
yet, and very vulnerable.

McALLISTER: So the next kind of
48 hours for this wee guy

is going to be quite extreme.

He's going to need a lot of care
to get him through.

Definitely out in the cold,

he wouldn't have
survived by himself.

NARRATOR: She'll feed him milk
every hour

for the next couple of days,
even through the night.

It's a critical time,

but they're
already beginning to bond.

McALLISTER: We've decided
to name him Billy,

and my job over the next
few days

would be to keep him nice
and warm, regular feeds,

and just overnight care
to make sure

that he is getting all the food
and comfort that he needs.

There you go, nice and snug.

NARRATOR: This is a rare chance
to follow a red squirrel

as he grows up.

If it all goes well,

we'll see Billy reach key
milestones in his development

and go back to the wild.

In the wild, he'd be tucked up
inside a nest.

Tree squirrels build nests from
twigs, moss, bark, and leaves.

The nest is known as a drey.

It keeps the young warm and safe
from predators

for the first
three months of their lives.

Females will have between one
and six babies in a litter.

And the young
are totally dependent

on their mother's care.

All tree squirrels depend
on a tree house

throughout their lives.

But the ground squirrels have
a different strategy

for keeping
their youngsters safe.

The rolling chaparral
of California.

Home to the California
ground squirrel.

They live in burrows...

where they can have their pups
in safety.

The pups won't poke a whisker
above ground

until they're at least
six weeks old.

♪♪

♪♪

When they do venture out,

the burrow is still
an essential bolt-hole

from predators like
birds of prey and foxes.

But burrows are no barrier
to their greatest enemy...

the Pacific rattlesnake.

♪♪

[ Squeaks ]

The snakes use infrared sensors

to detect the heat
of warm-blooded prey.

So there's nowhere to hide.

With pups to defend,
a mother must face the enemy.

♪♪

♪♪

She flicks stones.

It doesn't look like
the smartest move,

but it's a deliberate
and cunning ploy.

By provoking the snake,
a squirrel can listen

to the frequency
and speed of its rattle...

and this reveals how big,
how warm,

and how aggressive the snake is.

After listening, the squirrel
decides on her next move.

She pumps extra blood in to her
tail and waves it repeatedly.

The blood flow in her tail

is normally used to help
regulate temperature.

But now she knows
the extra heat

will be sensed
by the rattlesnake,

and it makes her seem bigger.

♪♪

It works!

Solving problems like this
can increase

a squirrel's chances
of survival.

It's something the pups
will need to learn, too.

Squirrel
babies have to grow up fast.

♪♪

Back in Scotland,
just three weeks have gone by,

but the change in Billy,
the little orphan, is clear.

McALLISTER: Hello.

NARRATOR: When she's not
at work, Sheelagh

brings him home to give him
the 24-hour care he needs.

McALLISTER: Billy's doing
really well.

He's feeding really good.

Gaining weight daily.

Billy's just opened his eyes
just last night,

so he's still not
quite sure of the light

and he's -- he'll still
squint his wee eyes

so he's just adjusting and
everything's still developing.

So he's starting to really look

like a proper
little red squirrel now.

He's clearly thriving,
and he's already developing

one of his most
vital life skills --

his grip.

McALLISTER: The grip that Billy
has is really important,

so it's going to
keep him in those trees.

You can see that, even so small,

he's got a good bit
of strength in him.

He kind of hooks these
nice wee claws into you,

which have grown
super-fast, as well.

At this stage, they would
still be in the nest

and they'd be pretty inactive,

so they would just be like
really kind of exercising

amongs

NARRATOR: Without his mother
or siblings to interact with,

Sheelagh will have to help
Billy practice his grip.

McALLISTER: Ooh!
Are you going up here?

Good lad!

NARRATOR: In the wild, having
strong claws and a firm grip

is a matter of life
and death up in the canopy.

It's a difficult place
to maneuver.

No two branches are ever
the same,

and conditions constantly change

with the weather
and the seasons.

Their aerial abilities
are so impressive,

they've captured the attention
of scientists

studying how animals move.

Professor Robert Full
is an expert in robotics.

Here at the University
of California at Berkeley,

he's already taken ideas
from cockroaches...

and bush babies.

And now he can see the potential
for squirrel-inspired robots.

FULL: A part of our motivation
is to understand

the most agile animals,
and squirrels

are certainly
among the most agile.

Imagine if we could understand
the fundamental principles

of how the squirrels move
through these complex,

unstructured environments

and then translate them
to robots.

Robots that, in a disaster area,
would be able to move

and jump through gaps
and climb on wires

to quickly enter an area
in order to find individuals.

NARRATOR: To study the squirrels
in detail,

the team uses a portable wall
out in the woods.

They stick perches to it that
represent branches of a tree.

A steady supply of nuts attracts
the wild squirrels in to play.

Bob is discovering their
aerial acrobatics

depend on their decision-making.

FULL: For example,
one of the tests we had is,

how could they determine where
to jump on branches or rods

that are of
different stiffnesses?

Some are really springy
and some are very stiff.

What would they do in order
to make the best choice

of jumping to the perch?

When it's very stiff,
they run out very far

and only jump a little bit.

That's the sort of
best decision.

NARRATOR: But when a branch
is very bendy,

they make a different choice.

FULL: They decide to only go
a little ways

and then take a longer jump,

so they make a very
good decision

in terms
of their jumping capability.

NARRATOR: All these choices
are made in a split second.

Bob is hoping to understand
these decisions

for the breakthrough
he wants in designing robots.

But his experiments have shown
something else, too.

If they do get it
slightly wrong,

it's their grip
that can save the day.

FULL: Even if they don't land
perfectly on the perch,

they have the ability
to maneuver their body

such that they're able to grip
and grab on with their claws

so that they don't fall,
and then they can swing back up

on the perch
to get their peanut.

NARRATOR: It's a brilliant
demonstration

of their grip in action.

And something Bob hopes

to replicate
with his robots in the future.

♪♪

One squirrel needs a good grip
more than most.

The jungles of southern India
are home

to the Malabar giant squirrel.

This remarkable-looking squirrel

is one of the most colorful
members of the squirrel family.

It's also one of the largest.

♪♪

At more than 3 feet long,

it's almost as big
as this lion-tailed macaque.

♪♪

The two compete for food, so
meetings aren't always friendly.

♪♪

Luckily there are plenty of
these huge jackfruit around.

They don't need to share.

Being such a heavyweight makes

the Malabar giant squirrel's
grip particularly impressive.

And that allows them to hang
upside down while they feed.

They also use their grip
to run down trees headfirst.

To help them do this,
they have a special adaptation.

An unusually flexible
ankle joint allows the foot

to rotate almost 180 degrees.

It's the equivalent of standing
with both feet

pointing backwards,

and means that whether
they're going down or up,

their claws are always
able to grip on.

This treetop technique is used
by all tree squirrels,

whether large...

or small.

And Billy's grip and strength
have improved by leaps

and bounds.

McALLISTER:
He is just over seven weeks now,

so we can see
he has changed quite a lot.

He's got this great bushy tail

and his agility's
really coming on.

He's getting very active
and quite a handful.

NARRATOR: To make sure Billy
can go back to the wild,

he needs to meet
some of his own kind.

McALLISTER: Hey, sweetie.

NARRATOR: And Sheelagh is now
caring for another youngster

of similar age.

McALLISTER: Hungry?

Yeah!

This is Annie.

She's from Inverness.

She was caught by a dog,

and the owner handed her
into the vet's,

so luckily she doesn't have
any injuries,

and for the size of her,
she's doing pretty well.

NARRATOR: It's an important
moment for Billy.

McALLISTER: Who's this?

Don't be scared.

At this age, in the wilds,

the squirrels
would have siblings

and they would also have
their mother, so you know,

it's just that contact
and being able to express,

like, natural behaviors
and just have playtime.

So it's really going
to benefit Billy,

as he's never had any contact
with another squirrel.

[ Chuckles ]

NARRATOR: They already seem

to be pushing each other
to new heights.

-McALLISTER: He's off.
-NARRATOR: It's a good sign.

McALLISTER: Come on Annie.
Whoo-hoo.

Annie.
Where you going, Billy?

What's your next move?

Billy!

NARRATOR: Young red squirrels
learn a lot

from interacting
with their families.

♪♪

But other species have taken
living together to the extreme.

♪♪

These are prairie dogs,
a type of ground squirrel.

They live in large colonies
called towns

all across the open plains
of North America.

The advantage of living
in numbers

is there are more eyes
to keep a lookout.

♪♪

When a coyote is spotted...

[ Squeaking ]

...they use a complex language
to warn the others.

♪♪

Their call communicates
more than just a warning.

It identifies
the kind of predator, too,

so they can take
the right evasive action.

So this coyote might be better
off trying its luck elsewhere.

These prairie dogs, it seems,
like to do things differently.

They eat mostly plants.

Not the diet you'd expect
from a squirrel.

And that's due to their size.

Big animals don't lose as much
body heat to the environment

as smaller ones.

So, as one of
the larger squirrels,

prairie dogs don't have to use
as much energy to keep warm...

and can survive on
a less nutritious diet.

It's a lifestyle that suits them
down to the ground.

[ Thunder rumbles ]

McALLISTER: What's in here?

NARRATOR: Smaller squirrels like
Billy need a lot more calories.

McALLISTER: Do you need some?

NARRATOR: That's why they depend
much more on nuts,

which are high in fat.

McALLISTER: Are you
going to take it?

Good boy.

NARRATOR: These almonds
are 49% fat --

ideal for a growing squirrel.

McALLISTER: So Billy has
just started to eat nuts.

He's like a wee
secret eater though,

like he just
hides out in his bed

and he'll eat
underneath the covers.

Last night was the first night
I've actually seen him

sit upright
and eat a nut,

which is quite
a good stage for him.

NARRATOR: For now,
he can only eat soft nuts

without the shells.

Although all his teeth
have come through,

they're still developing.

A squirrel's front teeth
never stop growing.

That's to counteract the wear

from a lifetime
of relentless chomping.

Red squirrel teeth grow around
8 inches a year,

so in Billy's life-span,

his teeth
may grow more than six feet!

Next, his tooth enamel
will harden.

It's a critical moment, because
then he'll be able to cope

with the hardest nuts in nature.

McALLISTER: Once he starts
eating the nuts in the shell

and being able
to break through this,

then we're quite happy for him
to be going to the wild then.

Ooh.

NARRATOR: Sheelagh hopes
to release Billy into the wild

during autumn at the time
when nuts are plentiful.

But as with squirrels all around
the world, winter,

when it finally arrives,
poses a real challenge.

There's little food around,
and the cold temperatures

mean using more energy
than ever to keep warm.

But squirrels everywhere have
come up with some ingenious ways

of surviving
the toughest time of year.

Here in Alaska...

3 feet underground...

the Arctic ground squirrel has
a particularly radical solution.

♪♪

It's hibernating.

It drops its heart rate,
breathing, and body temperature

and survives
on stored fat alone.

But that's not the really
clever part.

This little squirrel can handle

the coldest temperatures
of any mammal.

Even underground, it reaches
minus-15 degrees Fahrenheit.

The squirrel's body temperature
also drops below freezing...

yet the squirrel doesn't freeze.

We still don't know exactly
how that's possible.

What scientists have discovered
is, every two

to three weeks,
the squirrels shiver

to warm themselves
to a more typical 97 degrees.

This temporary warmth is just
about enough

to keep the squirrel
going through winter.

Spring arrives, and the ground
squirrel finally ventures out.

It's eaten nothing for a full
eight months.

But thanks to this remarkable
strategy,

it's slept through the lean
months of winter altogether.

♪♪

Other ground squirrels have

a different strategy
for success.

The chipmunks of North America.

One of the most endearing
members of the squirrel family.

Their small size means
they can't store enough fat

to sustain a complete winter
without eating.

So, although chipmunks will
sleep for days at a time

in winter
to save energy,

when they wake,
they need food to stay alive.

Luckily -- thanks to that hard
shell -- nuts store pretty well.

So they gather nuts
throughout autumn...

and stockpile them.

Chipmunks make hundreds of trips

backwards and forwards
to their pantry.

It takes a lot of time
and energy.

Flexible cheek pouches make
the task slightly easier...

...fitting in up to seven nuts
at a time!

But there is a problem.

Other chipmunks that want
to steal your stash.

A hoard must be defended,

even if it means
fighting for it.

♪♪

♪♪

♪♪

With the thief chased away,
the precious stockpile is safe.

It's everything a chipmunk needs
to get through the winter.

♪♪

But nuts are such a valuable
resource, theft is rife.

So, to avoid pilfering,

tree squirrels have come up
with a different tactic.

♪♪

They don't risk putting
all their nuts in one basket.

They bury each one separately.

It's a strategy known
as scatter hoarding.

But when hunger strikes,

how on earth do the squirrels
manage to find them again?

It's a question that intrigues
Dr. Mikel Delgado

at the University
of California at Berkeley.

Her university campus

is home to a thriving population
of fox squirrels,

the largest tree squirrel
in North America.

They provide the ideal
opportunity for Mikel

to discover what happens
to the nuts once they're buried.

DELGADO: We really don't know

how long it stays
where it was buried,

we don't know who retrieves it

and whether it gets reburied
or eaten or stolen.

I think a lot of people do think
that they're just, oh,

burying a nut wherever
and they might find it later,

but this is really a question
of survival for them.

NARRATOR: To find answers,

Mikel needs
to make each nut trackable.

So she drills a minute hole...

and inserts a tiny microchip.

To make them easier
for her to spot,

she paints the nuts with bright
yellow, nontoxic paint...

and puts them out
for the squirrels.

Squirrels are nut connoisseurs.

So Mikel watches
carefully to see

if her modified nuts
pass inspection.

DELGADO: The initial moment

that a squirrel receives a nut
and starts assessing it,

they're making a lot
of decisions.

Should I eat it now,
should I save it for later,

is this a nut that might go bad
if I bury it,

in which case, it's much better
to eat it now.

Well, they typically do
two assessment behaviors.

So you'll see paw manipulation

where they rotate the nut
in their mouth and paws.

And that allows them to see
if it's been infested

by a weevil or other insect,

and they're probably
also assessing the weight.

And then, shortly after that,
they usually do a head flick.

That allows the squirrel
to again determine,

is this a good nut,
is it old, is it fresh,

does it have
a lot of food inside.

And so those are the behaviors
that they use

to make their decisions
about where to bury a nut.

NARRATOR: Her nuts
pass the test.

Mikel scans the site
where the nut is buried

to record the precise spot.

DELGADO: We saw a squirrel
cache here earlier,

and now we're just checking

to get the exact location
with the scanner.

And now we will triangulate
this location

using different landmarks
and a compass

so that we can find it tomorrow
or a week from now.

NARRATOR: Using her notes,
Mikel can re-scan

every single nut
throughout the winter.

The ones that are moved are
assumed to have been remembered

and eaten,
or possibly stolen.

The nuts that are
never retrieved

are assumed to be forgotten.

The results are remarkable.

DELGADO: A year
and a half later,

we could see how many nuts
had been forgotten.

In my study, the squirrels

buried around 300 nuts

and of those nuts, about 10%

of them were forgotten.

So the flip side of that
is that squirrels

are probably remembering
and locating about

90% of the nuts they buried,
which is actually quite good.

NARRATOR: It's even possible
that some of the nuts

that weren't retrieved
were simply not needed

and not forgotten at all.

Mikel only supplied three
hundred microchipped nuts

in her experiment,

but fox squirrels
bury many more.

Each one can stash up
to 10,000 nuts a year.

Scaling Mikel's work up
suggests fox squirrels

can remember the exact location
of up to nine thousand nuts.

Impressive stuff.

So, is there something special
about the fox squirrel's brain

that allows them to do this?

♪♪

Dr. Lucia Jacobs thinks
there is.

Also at Berkeley, Lucia leads
research on the evolution

of brains and cognition.

JACOBS: This is the Berkeley
fox squirrel

and this species
is a scatter hoarder.

And this species is
a California ground squirrel.

You can see they're -- they're
pretty much the same size.

And these are both species that
are actually found in Berkeley,

and what's interesting about
pairing the ground squirrel

and the fox squirrel,
you can actually see,

even from their skulls,

how the brain size
is larger in the fox squirrel.

That's a general pattern
that's been shown -

that the tree squirrels
have larger brains.

NARRATOR: Remembering where
they've left their nuts

requires a bigger brain.

There's also another reason
why tree squirrels

are so blessed
in the brain department.

JACOBS: Arboreal animals
have larger brains

than animals that live
on the ground,

and it's just because
living in trees

is a much more
complicated environment,

and so you see that across
all kinds of different mammals.

The more that they're living
in a complex

three-dimensional environment,
the larger the brain.

NARRATOR: And that's not all.

Tree squirrel brains are able to
do something truly astonishing.

JACOBS: So what you may not know
about squirrels is that,

in the fall,
their brains get bigger.

So that squirrel in your
backyard, in the fall,

has a bigger brain
than the same squirrel

did earlier in the year.

NARRATOR: This is because they
have to make a huge mental map

of where all their nuts
are hidden,

and that takes brainpower.

By springtime, when food
is plentiful again,

the brain goes back down
to its smaller size.

Overall, Lucia thinks
the squirrel brain

is pretty impressive.

JACOBS: Squirrels are
very smart animals.

They're very long-lived,
even under natural conditions

of 5 years, but in captivity,
15 to 20 years.

And usually, animals,
the longer they live,

the larger the brains.

After all these years
with squirrels,

they really are special,
in fact, they are just --

the more I study them,
the more special they become.

♪♪

NARRATOR: Alongside
fox squirrels,

gray squirrels
are one of the smartest of all.

Their intelligence
and adaptability

to urban environments
have allowed them to become

one of the most
prolific squirrels on Earth.

♪♪

Wildlife filmmaker
Douglas Parker

is a squirrel fanatic,

and he's found a unique way
to demonstrate

just how smart
these wily grays are.

Tucked away
in an English woodland,

he's devised the perfect test
to see how they combine

problem solving
with their physical abilities.

Wild squirrels are attracted in
by a large pile of hazelnuts.

But to get to the nuts,

they must leap
between the colored discs.

The blue discs stand firm.

The red discs are wobbly.

The idea is that they'll learn
the difference,

and just use the stable blues
to get across.

But it's proving to be
a very difficult challenge.

PARKER: The squirrels will get
to the start...

quite literally just have
a look at it,

and think, nah, not a chance,

and just completely give up
before they even give it a go.

Others have given it a go
but fallen off halfway,

which is what I was expecting --
it's a very tough obstacle.

NARRATOR: Part of the learning
process is testing things out

and making mistakes.

♪♪

♪♪

But with their favorite nuts
in plain sight,

the squirrels
are utterly determined.

PARKER: So quick, so quick.
Oh, my gosh.

♪♪

NARRATOR: And finally, they find
their own way of getting across.

PARKER: The squirrels have
figured out

an incredible solution.

They take one step on the reds
and two steps

to steady themselves
on the blue.

So they go one, one-two, one,
one-two,

one, one-two,
using speed and agility

to overcome
the cognitive problem.

NARRATOR: Driven on by
their desire for nuts,

they've combined their grip,

persistence, memory,
and problem-solving skills.

♪♪

♪♪

And earned their prize
of a nice, big hazelnut.

♪♪

In the space
of just eight weeks,

Billy has developed many of
the skills

he'll need to succeed.

Now it's time to put them
all together.

To stand a chance of living back
in the wild,

he must leave the security
of Sheelagh's bedroom.

There's an enclosure back
at the rescue center,

which has been modified
to house Billy

and his fellow squirrel, Annie.

McALLISTER: It's really good
because we can set it up

with loads of different
branches,

hanging branches
and branches just going across,

and it also gets them used
to the elements,

as well, as having
a sheltered area.

NARRATOR: It's been set up
with everything

a squirrel could want.

But this is still a huge moment
for Billy,

and Sheelagh doesn't know
how he'll react.

McALLISTER: Hey, guys,
you're okay.

Hi, Billy, do you want
to come out?

Where are we?
Come on.

So, Billy has never encountered
anything outdoors --

he came into us
with his eyes closed.

Here we go.

NARRATOR: Billy and his
companion, Annie,

don't seem too nervous.

McALLISTER: Billy's
over -- [Laughs]

over there,
he's on his first branch.

He's venturing out
into the light. [ Chuckles ]

NARRATOR: And before long, he's
taking it all in his stride.

McALLISTER: We can see Billy's
quite happy,

he's going round
and exploring everything.

At times, you know, he'll just
kind of stop

and he's quite quiet and that's
when he's a bit unsure,

but he's doing really well,
he's jumping around

and he's gripping on
to everything real well.

He's doing good.

NARRATOR: The network of
branches inside the enclosure

is higher up and farther apart

than Billy
has ever experienced before.

It's to help him master
his next challenge,

the most difficult and dangerous
thing that all tree squirrels

have to do --

large leaps.

Jumping between branches avoids
a trip

all the way down to the ground
to get to another tree.

It saves a great deal of energy.

And despite the risk involved,

these incredible
feats of acrobatics

are an everyday part
of treetop life.

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♪♪

Their leaping is so impressive
that Dr. Greg Byrnes

has spent the last four years
trying to understand

how they can physically do it.

BYRNES: If you imagine this
animal jumping 8 to 10 feet,

that's, you know,
8 to 10 body lengths right,

that's a huge, huge jump.

NARRATOR: Here at his lab
in Siena College, New York,

Greg's enlisted an assistant
to find out more.

BYRNES: Okay, so this is Cedar.

This was an orphan squirrel
that we raised.

It was found on campus
maybe 2 months ago,

and so he's a juvenile
gray squirrel,

he's about 3 months old maybe.

We've hand raised it from a baby
and got it trained it jump

a little bit in the lab here,
and we can learn

some things about
the biomechanics of jumping.

NARRATOR: As soon as
he's big enough,

Cedar will gradually be released
back into the wild.

For now, he's honing his skills

by jumping between
two platforms,

in return for his favorite nuts.

BYRNES: Oh, there we go.
Oh, too far.

Here's a big nut.

NARRATOR: And Greg is analyzing
the mechanics of his leap,

with interesting results.

BYRNES: When it jumps,

it jumps with a maximum force
of about 10 body weights.

Compared to you or I,
I did a standing jump

about 6 or 7 feet
and I can produce about 1.5,

2 body weights, maybe, tops.

So they're much,
much more powerful jumpers.

NARRATOR: Greater power
equals a longer jump.

To produce more power, they have
especially large leg muscles.

The muscles act
like an elastic band,

so squirrels crouch
to pre-stretch them

for an extra
little snap of force.

♪♪

The next stage is flight.

BYRNES: It will then very
quickly extend its hind limbs,

its forelimbs will reach out

and basically start reaching
towards the target.

NARRATOR: The target
is the landing platform,

which Greg has modified.

It measures the pressure

Cedar puts down through
his paws on impact...

and reveals that the force
would be enough for Cedar

to hurt himself.

BYRNES: Then, when they land,
they can land with a force

of about 15 body weights,
and so they need to find ways

to basically reduce
that landing force,

and one of the things they do
is they make sure

they get all 4 limbs
on the ground at the same time.

NARRATOR: This spreads
the landing force

between all four feet.

Bending their legs also helps
absorb more of the impact.

Greg has discovered that
combining these adaptations

allows gray squirrels like Cedar
to complete huge leaps.

It's the equivalent of a human
jumping two bus lengths...

from a standing start!

♪♪

But there's another squirrel
who easily beats that record.

In the far north of America,

a nocturnal member
of the squirrel family

searches for fungi,
its favorite food.

But fungi are spread in random
patches throughout the forest,

and the squirrel has to cover
large distances to find them.

So this squirrel has evolved
a special talent.

It flies!

The northern flying squirrel
is just six inches long

and weighs the same
as a typical smartphone.

Yet it can leap almost 150 feet
between trees.

♪♪

Its "wings" allow it to glide
through the canopy.

Flying squirrels are
an incredible

piece of
aeronautical engineering.

♪♪

A large membrane stretches
between their wrists and ankles,

and another smaller membrane

runs between
the ankles and tail.

Combined, they form a parachute.

♪♪

Flying squirrels
have the longest limbs

of all the squirrels,

to make their parachute
as large as possible.

A piece of cartilage on the end
of each "wing"

gives them an upturned tip.

This reduces drag
and increases stability.

It's the reason many airplanes
have upturned tips

on their wings, too.

The result is these incredibly
long leaps

at speeds of up
to 20 miles an hour...

allowing the squirrels to travel
widely through the forest.

Billy has been building up
his strength and agility.

And now, he's ready to make
the biggest leap of all.

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♪♪

McALLISTER: So we are en route
with Billy and Co,

so this is release day,
so a big day for the guys.

So we've got a great location
for releasing them.

♪♪

NARRATOR: There are 50 acres
of woodland,

which will provide
plenty of food and space.

All Eurasian red squirrels range
far and wide as they forage.

Their favorite foods
are tree seeds.

Especially ones from pine cones.

And like most other tree
squirrels,

they have to
bury nuts for winter.

By Billy's age,

a wild squirrel would be fully
independent from its mother.

But Sheelagh won't be cutting
all ties just yet.

McALLISTER: So I've got a little
parting gift for Billy.

This is some whole hazelnuts.

If they don't want
to eat them now,

it just means
they can store them away

and keep them
for the wintertime.

NARRATOR: She'll put out nuts
daily through his first winter

so he can retrieve
and store them.

Finally, it's time for
the biggest step of his life.

The transport box allows Billy

to get used
to his new surroundings

while feeling safe
and hidden inside.

With the door open,
he can leave when he's ready.

McALLISTER: So he's just coming
to the front

and having a wee peek.

Just trying to suss
everything out

and then coming back in again.

He's coming out,
it's got his nose.

Bye, Billy!

NARRATOR: Now it's up to him.

McALLISTER: He's gone so high!

NARRATOR: It looks like Billy
has the speed

a wild squirrel needs,

and his instinct to head high
into the trees is a good one.

McALLISTER: It was good,
that was nice.

He went off quite calm,
had a good look around.

He maneuvered really well
in the tree.

I was quite happy with that.

He jumped out the box
quite relaxed and just that grip

on the tree,
maneuvered round the tree

and up to the top
in no time at all.

NARRATOR: And Billy
won't be alone.

♪♪

McALLISTER: I would say
it's a job well done.

Billy's really came along,

he's had quite a journey,
and, yeah,

he's just kind of proved
he's a wee champion.

[ Chuckles ]

NARRATOR: Back in the wild,
Billy will draw on

all the skills that he developed
during his time with Sheelagh.

He'll find his own home range
and build a drey for shelter.

Hopefully, by next year,
he'll meet a mate

and help bolster the numbers
of red squirrels in the forest.

As he gets to grips
with his new life,

he'll rely on all
the amazing abilities

that have made squirrels

one of the most successful
animal families

on the planet.

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To learn more about what you've
seen on this "Nature" program,

visit pbs.org.

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