(BIRDS AND INSECTS CHIRRUP)
(SNAP OF TWIGS)
100 million years ago, forests like these were just developing.
They 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 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 of the dinosaurs were sleeping.
As mammals, they could generate heat in their tiny bodies
so they could stay active in the cold night air.
Doing this burns a lot of food,
so they ate almost continuously, as shrews still do.
There's never enough food for a shrew,
and rivals fight over hunting rights with extraordinary ferocity.
(HISSING AND SQUEAKING)
This little insect-eater has now staked his claim
to the food in this part of the woodland.
When he meets a female, he's almost as aggressive towards her
as he is towards a rival male.
After testing one another's strength, the female accepts the male
not just as a contestant, but as a mate.
Two weeks later, the young are born.
The mother has nourished them inside her womb,
so they arrive comparatively well-developed.
Caring for the young is a crucial part
of mammals' ''winning design'', something few reptiles do.
A mother shrew even quenches her baby's 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 a mere two weeks
for the young to approach their mother in size.
They are now quite a handful
and need to be weaned from the nipple, despite their protests.
But the mother doesn't abandon them.
She herself leads them into the world outside.
The young have their own way of ensuring they don't get lost.
The first mammals lived alongside the dinosaurs for a long time.
But 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 very much the same small, scurrying little creatures.
That, in fact, is a very versatile body pattern,
and one of them, without much change, took to the water.
It hunts just as frenetically as its cousins do on land,
but it has a very different way of catching insects.
The water shrew's fur is oily and sheds water with a flick.
Its long whiskers help it feel for prey underwater.
Its ankles are hairy, so its feet act as paddles.
It shines like silver, glistening from the bubbles
trapped in its fur as it searches everywhere for prey.
Clinging to the underside of 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,
so the mole's eyes are covered in hairy skin
and its head has become a leathery wedge
with which it forces its way through the sand.
As it digs, the 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-pitch sound,
this mole detects very low ones,
like the faint vibrations made by foraging termites.
(WHIRRING)
Propelled by its flippers and guided by sound,
the golden 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 densely packed with nerve endings
that it 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.
One of these lives here, in the scrublands of East Africa.
This tiny pathway through the withered grass
is a sign that the insect-hunting rights for this part of the world are taken.
To advertise the fact, the owner has left a little pile of its dung.
But what could have made it?
To find out, I can use this tiny surveillance camera.
If I put that there...
then in front of it put some twigs across the path.
The creator of these runways is very fastidious
and, with luck, it will stop to clear away the twigs
and then give us a chance to have a good look at it.
This is the picture from the camera I placed
and this is from a camera further up the trail.
Now all I have to do is wait.
It's an elephant shrew.
He's not going to like that!
There you go. He's clearing his trail.
No.
Oh, dear! I'm afraid I've put in too much!
The elephant shrew, or ''sengi'', keeps its trails immaculate for good reason.
It sprints to evade its enemies.
Even the smallest twig could cause a disastrous stumble.
The goshawk has such keen eyesight that spotting a sengi is easy.
Catching one is another matter.
The sengi holds a map of its trails in its mind,
so 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 sengi,
and this gives them a crucial survival edge.
Daytime in the African bush is no place for the helpless.
Sengis are born to run.
Its appetite for milk is unquenchable,
for growing at this speed gives it constant hunger.
Its mother has nipples near her shoulders,
which are easier to reach and presumably help a quick get-away.
The baby will take solid food from its mother on its very first day, if it gets a chance.
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 race tracks.
(BIG BEN CHIMES)
Catching insects one by one takes a lot of time and energy,
and few creatures that feed that way
can get enough to build and sustain big bodies.
But some insect-eaters, early in their history, 40 million years ago,
solved that problem by broadening their diet.
And one of their descendants lives here in my garden in London.
I can tempt it out with a wide variety of food,
including, for example, minced meat.
The hedgehog is still very much a creature of the night,
but it's too big to hide in the leaf-litter,
making it vulnerable to attack from animals like foxes.
To make up for this, its hairs have become a cloak of prickles.
If it thinks it's in real danger, it's got a special trick.
It will stay an impregnable spiny ball like this
until it decides that danger has passed.
One thing is guaranteed to make a male hedgehog drop his guard -
the promise of an amorous liaison.
If you're outside on a spring evening,
you may be lucky enough to witness an extraordinary sight.
You might think having a coat of spines on your back
would be a handicap for the intimacies of courtship.
Classical naturalists thought hedgehogs actually mated
belly to belly!
The male noses the female's spines, which seems to excite her.
As far as he's concerned, it does look rather painful.
Whether the female flattens her prickles to help is unclear,
but it seems the old joke that asks
''How do hedgehogs mate?'' was right all along.
The answer is, of course, with great care.
The early American insect-eaters also had to protect themselves.
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 fastidious
and picks anything that looks edible.
(FRANTIC CHIRPING)
It still eats insects, but ants present it with a problem.
Its armour may protect it from large predators,
but it isn't a particularly good defence against small prey.
One extraordinary African insect-hunter has no such trouble.
It's a pangolin.
Those horny scales, like the hedgehog's prickles,
are made from modified hair.
It's front claws are so big, they're 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 muscular stomach and grind up the ants.
But these small underground ant colonies are mere snacks to a pangolin.
This is a real meal, a full-sized ants' nest.
There are a million or so of them here.
The pangolin smashes through the nest wall with formidable power.
Only an adult has the strength to do this,
so the young stay with their mother,
feeding in her wake until they're 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.
Mammals didn't always have ant colonies to feed on.
The rise of social insects,
60 million years after the first mammals,
was a landmark in evolution.
It was then termites and ants began 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 there are termite-eaters too.
Here in Brazil is the biggest of them all,
the giant anteater.
(WHISPERING) Its eyesight is very poor
and it relies mostly on its sense of smell, which is very acute.
If I keep downwind of it, I may not disturb it too much.
The truth is, ants and termites aren't very nutritious,
so the giant anteater has to try and conserve energy,
and one way 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.
It keeps its body temperature as low as any mammal, 32 degrees.
That means its brain doesn't work very fast.
It's not an animal with lightning reactions
or dazzling intelligence,
but you don't really need that if you're an anteater.
I think I'll 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 have shaped them in similar ways.
Both have big claws.
The giant's are the largest of any mammal.
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'm going to treat him with caution
because those huge claws and 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 claws and grip you.
It has been said that a 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 they drive it away.
Quick sampling like this does have an advantage.
The termites will soon replace the ones they've lost,
so in effect, it's harvesting the termite hills in its territory
in a way that ensures a continuous supply.
It may not have a dazzling intelligence,
but nothing exploits termites more effectively than the giant anteater.
To explore the origins of this extraordinary animal,
you 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 look remarkably familiar.
This is a tree anteater,
very like the tamandua anteater 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.
Alongside the anteater, the pangolin.
Once more, it has huge claws and no teeth.
Again, it looks identical to its living equivalent,
the African pangolin of today.
Why should these animals remain unchanged for 50 million years?
The rocks of Messel provide an answer to that too.
From them have come a termite -
more importantly, the queen of a termite colony -
and 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 perfect termite-eater?
Even back then, the majority of insects were airborne
and out of reach of ground-dwelling mammals.
One mammal followed the insects into the air,
and fossils of it have been found in the Messel deposits.
It's a bat.
Flight and the ability to catch insects on the wing
is an extraordinary achievement. How do bats do it?
This is a great place for bats, lots of insects flying around.
Birds are feeding on them as the bats sleep in their roosts.
Soon it'll get dark, and 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 during the day,
and by the mill stream there's a colony of Daubenton's bats
that are already stirring.
Their little faces are so like a shrew's
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
helped to extend those jumps, until eventually they could fly.
And how they can fly!
The change from a scurrying shrew to a fluttering bat
is the most magical in the whole history of mammals.
The bats' mastery of flight is so complete
that few insects can out-manoeuvre them in the air.
The bat scoops up the moth with the membrane around its tail,
then passes it forward to the mouth.
Their ground-living ancestors probably used sound
to find their way in the night-time forest, as shrews still do.
Bats then 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,
then listen to the echoes that bounce back.
Their brains then process these reflections
to give a three-dimensional image to their surroundings
and their prey.
(SQUEAKS AND CLICKS)
Moths, with their rather laborious flight,
are relatively easy to catch.
Some evolved a defence, a simple ear,
so when they hear the sonar of a bat approaching,
they can swerve out of the way.
So one bat changed tactics.
The long-ear doesn't hunt with sonar,
it uses its enormous ears to listen for prey.
It can even filter the faint sound of a moth's wing-beats
through the noise of the rushing water.
Its sonar guides it through the branches,
but as it approaches the moth, it 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 it's 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 doesn't make any noise at all,
so the bat can't locate it.
But sooner or later, the moth will have to move.
And that is its undoing.
How can a bat catch prey that is silent
in a place like this, so cluttered with vegetation
that echolocation shouldn't work?
These places are difficult to navigate but are full of food.
Spiders are more nutritious than moths,
but they're silent, venomous
and construct webs that are so strong
that a bat could become fatally entangled in the sticky silk.
Here comes Natterer's bat.
It seems aware of the almost microscopically thin 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 densest assemblages of mammals
found anywhere on the planet.
There are 12 million of them in this cave alone.
Where does such a vast number find enough food,
within flying distance of where they roost?
That puzzle baffled people for a long time.
Now we're discovering 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.
Starting from a number of points, each is the mouth of a cave.
Swarms are vast, with up to 20 million bats leaving each entrance.
Some fly low over Texas, but, curiously, most start to climb.
At 10,000 feet up, bats are so widely dispersed
that it's difficult to see them.
I've got with me my bat detector.
(HIGH-PITCHED BUZZ)
There's one, and that is a feeding buzz.
They're eating something, but what?
Already a kilometre above the ground, most are still climbing.
The radar picks up another front blowing in from New Mexico,
and the bats are flying towards it.
What could there be to 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,
and bats travel 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 tonnes of insects every night.
If bats have such ravenous appetites,
how do they survive winter when there are no insects around?
In Texas they migrate.
Here in Canada they have a truly radical solution.
(WHISPERING) Outside, it's 20 degrees below freezing.
Inside, icicles hang from the ceiling.
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.
More precisely, I'm losing energy as heat.
These little bats are blue because they are cold,
as cold as the rock to which they're clinging.
As the bats are no longer losing any heat to their surroundings,
they're using hardly any energy at all
and their metabolism has slowed down almost to a stop.
Although they're in the deepest hibernation,
they have to wake up every now and then to drink.
As they fire up their body chemistry,
their image on the thermal camera glows like a furnace.
Once awake, a male seeks out the slumbering females.
This one won't get a warm reception,
but he won't meet with much resistance either.
He'll mate with several more and then, after a drink,
he will return to sleep until the spring.
The power of 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 fragments of land
that were isolated in the South Pacific - New Zealand.
Here there were no cats, no rats, but lots of insects.
It was paradise for any insect-hunter.
So the bats flourished,
and their descendants are still here, somewhere.
To see them, I must wait for darkness.
(CREATURES CALLING)
This is the species I've 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 infra-red camera reveals
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 walk on their wrists with the finger bones pointing upwards
and slotted into a groove along the upper arm.
Now they're hunting as a pack.
Insects and small creatures fleeing from the jaws of one
run straight into those of another.
Worms are a favourite.
So much more satisfying than several hundred mosquitoes.
They don't want to share them with one another either.
They complete their meal with a drink of nectar
from the Hades plant that bloom flat on the ground.
They're this plant's pollinators.
Relationships between a plant and its pollinator
take a long time to evolve, so these bats
must have been scuttling over the New Zealand forest floor
for many 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 still have to contend with its powerful jaws.
The giant insect gains the upper hand...
..but it's soon overwhelmed by numbers.
These extraordinary bats now fight one another over its remains
with equal ferocity.
Evolution doesn't often go into reverse,
but it seems to have done so here.
After several million years of aerial combat,
these bats are reverting to the hunting techniques
of their shrew-like ancestors.
Mammals have pursued insects to the far corners of the earth.
They chased them up to the skies and back to the ground again.
The insect-eaters were there right at the beginning
of the rise of mammals, and they're still here today.
They're one of the great success stories in the life of mammals.