All language subtitles for The Life of Mammals 2of9 Insect Hunters 720p HDTV x264 AAC MVGroup org_Subtitles01.ENG

100 million years ago, forests
like these were just developing,

and were dominated by dinosaurs.

But as the giant reptiles slept,

tiny creatures were stirring.

They were the early mammals.

Despite this humble beginning,
their descendants would ultimately
take over the whole world.

Yet the rise
of this great dynasty was founded
on the most surprising diet.

Creatures very like those first
mammals are still around today -
shrews.

They hunted insects at night,

when most dinosaurs were sleeping.

They were able to generate heat
in their tiny bodies

so that they could stay active
in the cold night air.

But doing this burns a lot of food,
so they had to eat almost
continuously - as shrews still do.

There's never enough food
for a shrew.

Rivals fight over hunting rights
with extraordinary ferocity.

HISSING

This little insect-eater has now
staked his claim to the food
in this part of the woodland.

When he meets a female,
he is almost as aggressive towards
her as he is towards a rival male.

After testing one another's
strength, the female accepts the
male as a contestant and as a mate.

Two weeks later, the young are born.

Their mother has nourished them
inside her womb, so they arrive
comparatively well-developed.

Caring for the young is a crucial
part of a mammals' winning design -

something few reptiles do.

A mother shrew
will even quench her babies' thirst
with her own saliva if necessary.

Most important of all,

she provides them with
that uniquely mammalian food - milk.

This milk is so rich that it
takes just two weeks for the young
to approach their mother in size.

By this time, they are quite a
handful and need to be weaned from
the nipple, despite their protests.

Their mum doesn't abandon them. She
leads them into the world outside.

And the young have
their own particular way of
ensuring that they don't get lost.

The first mammals lived alongside
the dinosaurs for a very long time,

but then, about 65 million years
ago, when the dinosaurs so suddenly
and dramatically disappeared,

they had their chance
to colonise new environments.

At first, they remained much the
same - small, scurrying creatures.

But that is a versatile body
pattern, and one of them, without
much change, took to the water.

It hunts as frenetically as its
cousins do on land, but it has a
different way of catching insects.

The water shrew's fur is oily
and sheds water with a slight flick.

Its splendid whiskers are long
to help it feel for prey underwater.

Its ankles are hairy, so
its feet serve as excellent paddles.

It shines like silver, glistening
from the bubbles trapped within
its fur as it searches for prey.

Clinging to a root,
a dragonfly larva -

but the shrew's whiskers
don't touch it, and it's missed.

But not this time!

In Africa's Namib Desert, another
insect-hunter swims after prey -

but without a drop of water
in sight.

It's a sand swimmer -

a golden mole.

Sand, unlike water, scratches
and it isn't transparent either.

The mole's eyes are covered with
skin, its head a wedge with which
it forces its way through sand.

As it digs,

sand collapses behind it, making
it impossible for a tunnel to form,

so it doesn't dig through the sand -
it really does swim.

Sound travels well in sand.
Unlike shrews, which are adapted
to hear high-pitched sound,

this mole detects very low ones -

like the faint vibrations
made by foraging termites.

Propelled by its flippers and
guided by sound, the mole homes in

on its prey.

In North America, another mole
has paws that look like flippers.

These help it to swim under ice

to collect insects - but
this is not their primary purpose.

This creature is a digger -
a star-nosed mole.

Its paws are spades
for pushing aside soil,

while it tries to locate its prey
with its astonishing nose.

This has 22 fleshy arms.

Each is so packed
with nerve endings,

that the mole could touch a pinhead
with its nose in 600 places at once,

allowing it to locate
the tiniest of prey.

Living in soil rather than sand,

this mole can dig proper tunnels.

It constructs a labyrinth
of passages

and patrols them to collect
any prey that drops into them.

The star-nose, underground,
is largely beyond the reach
of predators.

Other insect-hunters, however,

run along trails above ground
and they are not so lucky.

And one of these trail runners
lives here in the scrublands
of East Africa.

This tiny pathway
through the withered grass

shows the insect-hunting rights
for this area have been taken.

To advertise the fact, the owner
has left a little pile of its dung.

But what could have made it?

Well, to find out, I can use
this tiny surveillance camera.

If I put that there

and then, just in front of it,
put some twigs across the path...

The creator of these runways
is fastidious and with any luck,

it will stop to clear the twigs

and then give us a chance
to have a good look at it.

This is the picture from the camera
I've just placed,

and this is from another camera
farther up the same trail.

And now all I have to do is to wait.

It's an elephant shrew!

He's not going to like that!

There you go.
He's clearing his trail.

Oh!

Oh, dear!

I'm afraid I have put in too much!

The elephant shrew or sengi
keeps its trails immaculate
for a very good reason.

It sprints to evade its enemies.

Even the smallest twig could cause
a stumble that could be disastrous.

The goshawk has such keen eyesight
that spotting a sengi is no problem.

Catching one is another matter.

The sengi holds a map of its trails
in its mind

so that in emergencies it can cut
corners to dive for cover.

Even a brush with death
doesn't put a sengi off its food.

Like all small insect-hunters,
it needs to constantly fuel
its internal fires.

That is especially important
when there are young to feed.

Incredibly,
this sengi is only a few hours old.

Few mammals are born
as well-developed as a baby sengi.

This gives them a survival edge.

Daytime in the African bush
is no place for the helpless.
Sengis are born to run.

Its appetite for milk
is unquenchable -

growing at this speed
gives it constant hunger.

Its mother has nipples near her
shoulders, which makes them easier
to reach and helps a quick get-away.

The baby will take solid food
from its mother on its
very first day if it gets a chance.

SCREECHING

With continued help from its mother,
the youngster will be
almost fully grown within a week

and be able to run as fast as her
along their racetracks.

Catching insects one by one takes
a lot of time and a lot of energy,

and very few creatures
that feed that way can get enough
to build and sustain big bodies.

But some insect-eaters,
about 40 million years ago,

solved that problem
by broadening their diet.

And one of their descendants lives
right here in my garden in London.

And I can tempt it out
with a wide variety of food,
including, for example, minced meat.

The hedgehog is
a creature of the night, but
it's too big to hide in the leaves.

That makes it vulnerable to attack
from animals like foxes.

To make up for this, its hairs
have become a cloak of prickles.

And if it thinks it is in real
danger, it's got a special trick.

The hedgehog will stay
an impregnable spiny ball like this

until it decides
that danger is passed.

But one thing is guaranteed to make
a male hedgehog drop his guard -

an amorous liaison.

If you are outside
on a spring evening,

you may be lucky enough to witness
an extraordinary sight.

You might think that having
a coat of spines on your back

would be something of a handicap
when it comes to the intimacies
of courtship.

Classical naturalists thought
that hedgehogs actually mated

belly to belly.

The male noses the female's spines,
which seems to excite her.

Although, as far as he is concerned,

it does look rather painful.

Whether the female flattens
her prickles to help the male
is unclear,

but it does seem that the old joke
that asks, "How do hedgehogs mate?"
is true.

The answer is, of course,
with great care.

The early American insect-eaters
also needed to protect themselves,

but they did so, not with spines,
but with armour plating.

Armadillos, like hedgehogs, grew
large by broadening their diet.

Their tastes change
with the seasons.

Fruit is easy to collect, but the
nine-banded armadillo is not fussy

and will pick up anything
that looks edible.

It still eats insects,

but ants present it with a problem.

Its armour protects it
from large predators, but it isn't
good defence against small prey.

One extraordinary African
insect-hunter has no such trouble.

It's a pangolin. Its horny scales,
like the hedgehog's prickles,
are made from modified hair.

Its big front claws
are useless for walking.

It trundles along on its hind legs,

balancing its torso with its tail.

Its front claws are reserved
for digging up ants.

As it does so, it swallows stones.

They accumulate in its stomach
and help to grind up the ants.

But these
small underground ant colonies

are mere snacks to a pangolin.

This is a real meal -
a full-size ants' nest.

There are a million or so of them
in here.

The pangolin smashes through
the nest wall with formidable power.

Only an adult
has the strength to do this.

Young ones stay with their mother,
feeding in her wake until they are
big enough to dig for themselves.

The angry ants swarm
all over their attacker,

but the pangolin's armour
is a very effective defence.

Its eyes are protected
by thick lids,

and its nostrils and ears
have special valves
to keep the biting insects out.

For its size, the pangolin has
the longest tongue of any mammal -

and the stickiest saliva.

But mammals didn't always have
ant colonies to feed on.

The rise of social insects, 60
million years after mammals arrived,
was a landmark in evolution.

It was then that termites and ants

started to build huge nests,
each containing
millions of individuals.

Here was so much food
that insect-eaters could grow big.

There are termites in the Americas

just as there are in Africa,

so of course,
there are termite-eaters, too.

And here in Brazil is the biggest
of them all - the giant anteater.

Its eyesight is very poor

and it relies mostly on its sense
of smell, which is very acute.

But if I keep downwind of it,

I may not disturb it too much.

The truth is that ants and termites
aren't very nutritious,

so the giant anteater has to do
all it can to conserve energy,

and one way of doing that
is to sleep for 15 out of 24 hours.

It covers itself, too,
with that big bushy tail

to reduce heat loss to a minimum.

And it also keeps its body
at as low a temperature
as any mammal - 32 degrees.

That means, of course, that
its brain does not work very fast.

It's not an animal with lightning
reactions or dazzling intelligence,

but then you don't really need that
if you are an anteater. And now
I think I will get out of its way.

Termite mounds are more numerous
here than anywhere,

but the challenges facing
a termite-eater are considerable.

Anteaters and pangolins
have different ancestors

but the demands of their diet
has shaped them in similar ways.

Both have big claws - the giant's
are the largest of any mammal -

and both have an immensely
long tongue that slips through the
tube formed by the toothless jaws -

so that both can virtually drink
termites.

He may lack teeth, but I am going
to treat him with caution,

because, in fact, those huge claws
and those powerful front legs
can be very dangerous.

He can rip apart this termite hill,

and if he wants to defend himself,

he will use those big bowed legs
and their claws and grip you.

It has even been said that
the carcass of a jaguar was found
in the embrace of one of these.

It only collected a few hundred
termites on that brief visit.

As soon as it breaks into a mound,
the inhabitants attack it so
ferociously that they drive it away.

But quick sampling like this
does have an advantage.

The termites will soon replace
the ones they have lost, so, in
effect, the anteater is harvesting

the termite hills in its territory

to ensure a continuous supply.

It may not have
a dazzling intelligence,

but nothing exploits termites more
effectively than the giant anteater.

If you want to explore the origins
of this extraordinary animal,

you would have to go
to a very surprising place.

I'm near Messel in Germany.

Behind me is a quarry rich in
the fossilised remains of animals
that died 50 million years ago,

and that was a pivotal time
in the history of the mammals.

Even though these animals lived
a very long time ago, some of them
look remarkably familiar.

This is a tree anteater,
very like the tamandua anteater
that lives in South America today.

All the insect-collecting equipment
is there -

huge claws on the front legs,

no teeth, and jaws fused
into a tube, through which
a long tongue would have flicked.

And alongside the anteater,
the first known pangolin.

Once more it has huge claws -
no teeth.

And again it looks identical
to its living equivalent,

the African pangolin of today.

Why have these animals remained
unchanged for 50 million years?

The rocks of Messel provide
an answer to that.

From them has come a termite -
more importantly,
the queen of a termite colony.

It's the same in every important
respect as its living relatives,

and this is the key.

If termites haven't changed
for 50 million years, why change
the design of the termite-eater?

Even back then, the majority
of insects were airborne and out
of reach of ground-dwelling mammals.

But one mammal followed the insects
into the air,

and fossils of it have also
been found in the Messel deposits.

It's a bat.

The ability to catch insects
on the wing is an extraordinary
achievement. How do the bats do it?

This is a great place for bats.
There are many insects
flying around.

Just now, birds are feeding on them
and bats are asleep in their roosts.

But soon, it will get dark

and then the birds will go to roost
and the bats will come out
to claim their share.

At night,
there are even more flying insects
than there were during the day

and by the mill stream
is a colony of Daubenton's bats
that are already stirring.

Their faces are so like a shrew's

that it's easy to imagine
shrew-like ancestors in the trees,
jumping from branch to branch,

chasing insects.

Ever larger flaps of skin between
their fingers extended those jumps

until, eventually, they could fly.

And how they can fly!

The change from a scurrying animal
like a shrew to a fluttering bat

is surely the most magical
in the whole history of the mammals.

The bats' mastery of flight
is so complete

that few insects
can outmanoeuvre them in the air.

The bat scoops up the moth
with the membrane around its tail

and passes it forward to the mouth.

Their ground-living ancestors
probably used sound

to find their way in the night,
as shrews still do,

but bats perfected that technique,
using sound frequencies
beyond our hearing.

A bat detector
makes those calls audible to us.

Bats emit high-intensity pulses
of sound and then listen
to the echoes that bounce back.

Their brains
process these reflections

to give them a 3-D image
of their surroundings

and their prey.

Moths, with their laborious flight,
are relatively easy to catch.

But then some evolved a defence -

a simple ear, so that when they
hear the sonar of a bat approaching,
they can swerve out of the way.

So, one bat changed tactics.

The long-eared
doesn't hunt with sonar.

It uses its enormous ears
to listen for prey.

It can filter the sound
of a moth's wing beats

through the noise
of the rushing water.

Its sonar guides it
through the branches,

but as it nears the moth, it turns
that off and enters "stealth mode".

Now it's guided solely by
the noise of the moth's wing beats.
But the system isn't perfect.

The bat can hear the moth
through the leaf

and is approaching it
from the wrong side.

A lucky escape for the moth.

But now the bat has come round
to the other side.
If the moth stays still,

it makes no noise,
so the bat can't locate it.

But, sooner or later,
the moth will have to move.

And that is its undoing.

But how could a bat catch prey
that is silent in a place like this,
so cluttered with vegetation

that echolocation shouldn't work?

These places are tricky to navigate,
but full of food.

Spiders are more nutritious than
moths, but they're silent, venomous,

and construct webs so strong
that a bat could easily become
entangled in the sticky silk.

Here comes Natterer's bat.

It seems well aware of the almost
microscopically thin silken threads

and, with surgical precision,
removes the spider from its web.

It even reverses away from the web
to avoid getting entangled.

To detect the threads and recognise
on which side the spider is sitting

must be the ultimate refinement
of sonar.

Mexican free-tailed bats.

They form some of the biggest and
the densest assemblages of mammals
to be found anywhere on the planet.

There are 12 million in this cave.

But where do such a vast number of
individuals find food within flying
distance of where they roost?

That puzzle
baffled people for a long time.

But now we're beginning to discover
what they feed on and where they
find it - and it's very surprising.

A few years ago,
pilots flying above Texas reported
seeing bats at high altitude.

Scientists investigated
and made an extraordinary discovery.

As I climb into the evening sky,
the weather conditions seem good.

But the local weather radar
shows a storm nearby,
growing with alarming speed.

However, I needn't worry.

This is not a storm. It's the bats
we just left, leaving their roost.

They start from a number of points,
each the mouth of a different cave.

The swarms are vast, with up to 20
million bats leaving one entrance.

Some fly low over Texas,

but, curiously, most start to climb.

At 10,000 feet up,
bats are so widely dispersed

that it is very difficult
to see them,

but I've got my bat detector.

HIGH-PITCHED CLICKING
And there's one. And, what is more,
that is a feeding buzz.

So, they're eating something.
The question is - what?

They're a kilometre above the
ground and most are still climbing.

But now the radar picks up another
front blowing in from New Mexico

and the bats are flying towards it.

What could attract them
to these great heights?

Scientists find out what's
flying high in the sky at night
with a device like this.

And in it...

moths.

Vast numbers of these insects use
the prevailing winds at altitude

to travel from the tropics to feed.

Bats climb up to three kilometres
into the night sky to catch them.

Bats are so numerous and
so voracious that the individuals
in this one cave below me

eat 120 tons of insects every night.

So, if bats have
such ravenous appetites,

how do they survive in the winter,
when there are no flying insects?

In Texas, they migrate.

Here, in Canada,
they have a truly radical solution.

Outside,
it is 20 degrees below freezing.

Inside,
icicles hang from the ceiling.

And yet
these little brown bats can survive

throughout the winter
without a single meal.

How do they do it?

The thermal-imaging camera
is showing my face

as red and orange.

That's because it's warm.
I'm a mammal.

Putting it more precisely,
I am losing energy as heat.

But these little bats are blue,
because they are cold -

as cold as the rock
to which they are clinging.

As the bats are no longer losing
any heat to their surroundings,

they are using hardly any energy

and their metabolism
has slowed down almost to a stop.

Although in the deepest hibernation,

they have to wake up now and then
to have a drink.

As they fire up
their body chemistry,

so their image on the thermal
camera glows like a furnace.

Once awake, a male seeks out
the slumbering females.

He won't get a warm reception
to his advances,

but he won't
meet with much resistance either.

He will mate with several more

and then, after a drink, he will
return to sleep until the spring.

Flight not only enabled bats
to catch insects in the air -

it also allowed them
to extend their range

far beyond that of any other mammal.

Bats were the first mammals to find
their way to some fragments of land
isolated in the South Pacific -

New Zealand.

Here, there were no cats, no rats,
but lots of insects -

paradise for any insect-hunter.

So, the bats flourished
and their descendants
are still here...somewhere.

To see them,
I must wait for darkness.

And this is the species
I have been waiting for.

These bats look normal enough,

but bats are aerial predators
and much of the uneaten prey
in New Zealand is on the ground.

They can fly all right,

but our infrared camera reveals

that they also have
a very un-bat-like way of hunting.

They land on the ground
and forage through the leaf litter,

just like shrews.

They are walking on their wrists,

with the bones of their fingers
pointing up and slotted
into a groove along the upper arm.

Now they seem to be hunting
as a pack.

Insects, or other small creatures
fleeing from the jaws of one,

run straight into those of another.

Worms are a great favourite -

so much more satisfying
than several hundred mosquitoes -

and they don't want to share them
with one another either.

They finish off
with nectar from the Hades plant,
that blooms on the ground.

They are this plant's pollinators.

Relationships between a plant and
its pollinator are slow to evolve,

so these bats must have been
scuttling over the New Zealand
forest floor for millions of years.

Worms and nectar are easy prey,
but what about this?

It's a weta,

a giant flightless cricket
with spiny legs and ferocious jaws.

How could bats whose ancestors
ate mosquitoes tackle this?

The weta can flick its back legs
forward with surprising force.

Even if you dodge that, you have
to contend with its powerful jaws.

The insect gains the upper hand...

..but it's soon
overwhelmed by numbers

and the bats fight one another over
its remains with equal ferocity.

Evolution doesn't often go into
reverse, but it seems to have here.

After several million years
of aerial combat,

these bats are reverting to
the techniques of their ancestors.

Mammals have pursued insects
to the far corners of the earth.

They've chased them into the skies
and back down to the ground.

The insect-eaters were there
right at the beginning of the rise
of mammals, and they are still here.

They are one of the great success
stories in the life of mammals.

Bats are surely
one of the most magical of mammals,

but they're also
one of the most mysterious,

as they see the world in a way that
is utterly different from our way.

It's SO different that
we didn't even know what it was
until about 60 years ago.

The action of Natterer's bats
plucking spiders from their webs
has never been filmed before.

The shots show the precision of
their flight and their echolocation.

How did we come to understand the
bat's extraordinary use of sound?
That's what we'll discover now.

The story starts in 1941,

when an American biologist
called Don Griffin was working
with physicists at Harvard,

using a revolutionary
ultrasound detector.

When a bat flew at him,
he became the first human
to detect the sounds it was making.

They were very loud
and very high-pitched.

This discovery launched a series
of experiments to prove that the
bats have a sort of airborne radar,

an invention
then being used in aeroplanes.

Yet bats could detect tiny targets,

processing their echoes
in a brain weighing half a gram.

When echolocation was discovered,
in the 1940s,

Don Griffin and Robert Galambos

presented the findings at a meeting.

There was such disbelief with the
suggestion that bats use echolocation

that one of the scientists
came up to Galambos,

took him by the lapels forcefully,
and said, "This cannot be correct."

But Griffin continued testing the
bats' ability to avoid fine wires

in the flight cages at Harvard.

By 1960, it was clear that
echolocation provided the bats with
a detailed sense of their world.

New technology
helped to explore that world.

Using high-speed tape recorders
to slow down calls

showed different species used sound
differently, to suit their habitat.

The intensity of bat echolocation
calls really varies tremendously.

At one extreme are "whispering bats",

that we can barely detect
on some of our equipment.

At the other extreme,
there are bats that can make calls
as loud as 130 decibels.

To put this into context,
the threshold of pain in human
hearing is round about 126 decibels,

so these calls would be
painful to us, if we could hear them.

The calls are loud in order to
produce clear echoes for the bat

and, to cope, the bat goes
temporarily deaf on each call,

by synchronising the nerve impulse
of the call with a muscle in the
ear, which disconnects the eardrum.

This may happen 120 times a second,

one of the highest rates
of muscle contraction of any mammal.

And, of course,
it's what the bats hear that
creates their view of the world.

Understanding that
was a more complex problem.

In the '80s,
Trachops, the fringe-lipped bat,

was studied by American scientists
Merlin Tuttle and Mike Ryan.

Using ultrasound,
the bats navigate effortlessly
through the Panamanian rainforest,

but their hunting strategy
was extraordinary.

These bats go for a large prey -
the mud puddle frog.

Collecting them in the forest and
testing them in a jungle laboratory

showed that they could distinguish
different kinds of frog calls
played through a loudspeaker.

As soon as we turned on the set,
the bat just took off from its perch,

made a beeline to the speaker...
It was obvious that this bat thought
there was a frog inside that box.

By playing different tapes,

they established just what the bats
were able to hear in the frog calls.

Then they tested their findings
back in the forest.

Studying bats in the wild
is notoriously difficult,

but it's a vital step
to understanding any animal.

Whispering bats, like Trachops
and the British long-eared bats,

rely only on hearing to catch prey.

They can hear
the rustling of moth wings

and pluck them from bushes.

But most bats intercept insects
by patrolling the air,

listening to the echoes
of their own calls and attacking
the ones returned by their prey.

We know that the wavelength of
the call is designed to produce the
best echo from moth-sized objects,

and that the bat increases
the rate of calls as it homes in
on the target, for greater accuracy.

This is the "feeding buzz".

It's extraordinary
how fast the action happens.

We use bat detectors
to hear the calls and high-speed
filming to slow the flight,

simply to appreciate the behaviour.

These bats can fly
six metres in a second
and may catch 25 moths in a night.

The studies in the wild
have also identified a wide range
of different call signatures.

Each is suited
to a different habitat.

The calls of woodland-edge bats are
distinct from those of forest bats,

and from ones that hunt over water.

By using different frequencies
and duration of call,

different species of bats
have adapted to different habitats
and hunting techniques.

Their ecology is based on sound.

Although research
during the last 60 years
has revealed extraordinary details

about the way in which bats
find their way around and hunt,

there's still a great deal to learn.

How does the bat's brain
process the information?

We know that the strongest echoes
will be right in front of the bat,
so they have a narrow field of view,

and by using a wide spectrum
of call frequencies,

the bat's brain may convert the
echoes into an equivalent of colour.

But can their
sound perception system be
as accurate as our colour vision?

One of the challenges
is trying to work out

how the nervous systems
of these animals cope.

In terms of time,
we know from laboratory studies

that bats can make discriminations
in the order of ten nanoseconds.

A nanosecond
is a billionth of a second.

In terms of distance, this
corresponds to a difference in range
in the order of two micrometres.

Some scientists argue
that animals just cannot make
these sorts of discriminations,

given what we know about their
nervous systems, so the challenge
is trying to work out how bats do it.

And our sequence of the Natterer's
bats may help to solve that mystery.

To detect a thread of spider's web
from its echo
is truly extraordinary.

Next week, in The Life Of Mammals,

we meet predators
that prey on plants.

They are forced to fight battles
with their highly-defended prey,

with one another,

and with the meat-eaters
that would eat them.