NARRATOR: All around the planet, billions of animals are on the move... ...making incredible journeys.

The most amazing of these are the smallest.

This series uses the latest camera technology to follow six tiny animals on the biggest adventures of their lives as they travel through extraordinary landscapes... ♪♪ ...where every little step counts.

♪♪ ♪♪ The greatest adventures are the smallest.

♪♪ ♪♪ ♪♪ ♪♪ Kirindy Forest, Madagascar.

♪♪ This tiny chameleon is a few minutes old... ...half the size of a matchstick.

She has spent seven months underground, developing inside her egg.

And now her own eggs are already growing inside her.

♪♪ She's starting a journey to find a male.

These chameleons only live for a matter of months.

Her instincts drive her to climb.

♪♪ Built for the ascent, her feet can swivel... ♪♪ ...helping her cling to cracks.

She heaves her way upwards.

The climb is 150 times her body length, like a human scaling the Empire State Building.

16 feet up, she's in a very different world... ...a dense network of branches that give shade and create aerial highways.

[ Insects chirping, birds calling ] She's hungry.

[ Flies buzzing ] She has never eaten before, but she knows food when she sees it -- flies.

[ Buzzing ] They have split-second reflexes, but she's born with the skills of an assassin.

Her eyes search almost 360 degrees.

A target.

Both eyes lock on with binocular vision.

And she fires her lightning-fast tongue.

♪♪ ♪♪ It's twice the length of her body and as sticky as honey.

♪♪ ♪♪ She catches up to 100 flies a day.

In just two weeks, she's doubled in size.

[ Flies buzzing ] [ Animals calling ] The fading light and decreasing accuracy is her cue to get some sleep.

Being light on her feet, she can reach places where most predators can't.

The thinnest branches are the safest.

Her pincer-like feet clamp onto the branch.

It's like sleeping on a tightrope.

♪♪ ♪♪ A cat-eyed tree snake... ♪♪ ...it's still light enough to reach her.

Deep in slumber, the chameleon is at her most vulnerable.

♪♪ The snake's approach causes tiny vibrations along the branch that the chameleon can sense, even when asleep.

♪♪ And when the snake is too close, they wake her up.

♪♪ All she can do is let go.

♪♪ Her radical move is a deliberate escape strategy.

[ Owl hoots ] But it has put her right back on the dangerous forest floor in the middle of the night.

♪♪ 6,000 miles away, the Cairngorms of Scotland... ...home to one of Britain's shyest animals... ...a water vole.

This female is three months old and small enough to fit in the palm of a human hand.

She is busy preparing her small territory by digging burrows, ready to raise a family.

She must eat two-thirds of her body weight every day to stay in prime condition.

There's just a few weeks left to mate and raise pups before the first signs of winter.

To attract a suitor, she strategically leaves droppings around her territory.

[ Insects chirping ] Today, she's got some attention... ...a vole's worst nightmare... ♪♪ ...an invasive American mink.

♪♪ Its ultrasonic hearing can detect the slightest squeak.

To a water vole, its odor is a trigger... to run.

♪♪ Just one mink could wipe out every vole in this glen in just a few weeks.

♪♪ She's lost her riverbank home.

♪♪ ♪♪ She must now travel into the unknown to find a new territory in which to have her first pups.

♪♪ ♪♪ Two miles into the glen... ...she's alone, homeless, and exhausted.

♪♪ She needs a place to rest.

A burrow.

She could make it her new home.

♪♪ ♪♪ It's occupied.

A pregnant water vole.

This is her burrow, and she will fight to the death to defend it.

[ Voles squeaking ] ♪♪ Being less experienced, the best option is to flee.

[ Water lapping, insects chirping ] But the path ahead... is blocked.

♪♪ Back in Madagascar, with her biological clock rapidly ticking away, the chameleon is searching for a way back up into the trees.

♪♪ ♪♪ ♪♪ ♪♪ She's unaware of the predators that lurk in the dark.

♪♪ Her brown, mottled skin helps her to blend into the leaf litter.

♪♪ ♪♪ ♪♪ Could this tiny twig lead her up?

♪♪ ♪♪ No.

It's a stick insect.

♪♪ ♪♪ As she travels, her cover disappears.

♪♪ ♪♪ She's on a dirt track cut through the forest by humans.

♪♪ ♪♪ ♪♪ ♪♪ Drawn towards a tree trunk, she hauls herself upwards with every ounce of energy she has left.

♪♪ ♪♪ Finally, she can get back to sleep.

♪♪ ♪♪ Dawn reveals a harsh reality.

♪♪ ♪♪ Once, there were trees all the way to the horizon.

[ Wind whooshing ] Now there is nothing.

♪♪ It's a long way back.

♪♪ ♪♪ ♪♪ ♪♪ Finally, in the safety of a tree... ...but she's facing another problem.

Being shaken off is the last thing she needs.

[ Leaves rustling, animals calling ] Red-fronted lemurs.

[ Lemurs grunting and calling ] Feeding on the fruit in this neem tree, they've created a sticky mess... ...a magnet for flies.

[ Flies buzzing ] A chance to get her energy back before she continues her journey to find a mate.

Far away in Scotland, the vole's search for a new home has taken her three miles into the glen.

Ahead of her lies water.

She's spent her entire life around streams.

But with poor eyesight, she has misjudged how far it is to the other side.

[ Birds calling ] This loch is vast.

♪♪ In the cold waters beneath her, monsters lurk.

Giant pike, four times her size, could swallow her whole... ♪♪ ...if she doesn't drown first.

She's never swum more than a few feet from land before.

♪♪ The farther she swims from shore, the more likely she will be detected.

♪♪ Once a pike senses ripples... ...most prey don't stand a chance.

♪♪ ♪♪ But this water vole has made it to the other side.

♪♪ ♪♪ For now, she's safe.

♪♪ Running water... ...it's the sound of home.

♪♪ ♪♪ ♪♪ If she follows it, she might find the habitat that she's looking for.

The higher she climbs, the rockier it becomes.

600 feet up, there's trouble.

♪♪ ♪♪ [ Bird screeches ] A golden eagle... 30 times bigger than a water vole.

♪♪ With vision five times more powerful than a human's, it could spot a vole from more than a mile away.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ [ Eagle squawks ] She will have to sleep here tonight.

[ Insects buzzing, birds calling ] In Madagascar, four months have passed, and the chameleon has reached a pivotal moment in her short life.

She has undergone the most extraordinary transformation.

♪♪ She has become an adult.

♪♪ ♪♪ ♪♪ Now as long as a human finger, her skin is a kaleidoscope of color... ♪♪ ...created by special light-reflecting nanocrystals in her skin cells.

A chameleon's color is primarily used for communication, and it changes with her mood.

Her most important signal is a crimson spot... ...indicating that she is ready to mate.

Her eggs are fully grown and visible through her skin.

Now she needs to find a male to fertilize them.

She needs to secure an area to show off her colors... ...but every female of her species is on the same biological clock... ...all vying for the attention of a male.

Already, she has competition.

♪♪ ♪♪ Females can't risk damage to their delicate eggs.

They rarely make contact.

♪♪ Instead, they rely on elaborate warning displays.

She attacks from below.

[ Chameleon hissing ] ♪♪ Having forced her rival away... ...she has claimed this area as her own.

♪♪ ♪♪ She can now dazzle her colors.

♪♪ ♪♪ [ Fly buzzes ] ♪♪ ♪♪ She's attracted a male.

♪♪ ♪♪ There are two.

They must prove their worth.

♪♪ They are twice her size and built for combat.

The bigger the nose horn, the more attractive the male... ...and the taller the head crest, the more powerful the bite.

These two gladiators are evenly matched.

She monitors every movement from a safe distance.

The most dominant male will pass on the strongest genes.

♪♪ ♪♪ They must fight it out to win her favor.

[ Chameleon hisses ] [ Chameleons hissing ] Unlike females, they don't hold back.

♪♪ ♪♪ This could be the last battle of their lives, before they die.

♪♪ ♪♪ ♪♪ It will only end when one backs down... [ Chameleon hisses ] ...and falls.

She allows the victor to approach.

After mating, they will never see each other again.

With her eggs fertilized, there is only one more stage of her journey to complete... ...to find a safe place to lay them, before her life comes to an end.

♪♪ The water vole is now five miles from her old riverbank home.

♪♪ ♪♪ Her search has taken her to altitude.

♪♪ She's in alien territory... ♪♪ ...but keeps climbing.

♪♪ ♪♪ ♪♪ She's over 2,000 feet up.

Before her lies a new frontier.

♪♪ With the threat of the eagle, she must move on quickly.

♪♪ ♪♪ [ Bee buzzing ] She's lost a lot of weight and is depleted of minerals.

She'll need more than just grass, to get her strength back.

[ Deer lowing ] Red deer.

They may provide just what she needs.

An old stag's antler, packed with minerals.

A hundred times more calcium than milk.

She's not the first vole to have taken a bite here.

A few nibbles is all she needs.

♪♪ ♪♪ And then an adder, the U.K.'s only venomous snake.

♪♪ Being cold-blooded, it's basking in the sun to warm up.

♪♪ A bite from an adult could kill.

But, luckily for the water vole, this one isn't yet fully grown.

Neither vole nor snake is a threat to the other.

♪♪ Finally reaching the valley floor, she has entered prime water-vole habitat... ...and there's a burrow.

She is wary.

There is something here... ♪♪ It's just a harmless toad taking shelter.

[ Water vole squeaking ] With no sign of a resident water vole, she's found a new home.

If she can find a mate, she will still have time to raise a family.

With darkness falling, she can rest.

♪♪ Back in her forests, the chameleon is 5 months old and has reached old age.

♪♪ Nearing the end of her journey, she must find the perfect spot to lay her eggs.

♪♪ She has no time to waste on an approaching male.

♪♪ [ Chameleon hisses ] He's too late.

[ Chameleon hisses, screeches ] ♪♪ Puffing up her body and expanding her skin cells, she turns from green to black... ♪♪ ♪♪ ...a clear signal to back off.

♪♪ Instinct drives her towards the forest floor.

♪♪ ♪♪ ♪♪ Now a beacon of color, she stands out amongst the leaf litter... ♪♪ ...and is slower... ...weighed down by eight eggs, a third of her body weight.

She needs to head away from tree roots, to a place where she can dig... ♪♪ ...and with just the right amount of sunlight to incubate her eggs.

♪♪ With every step, she could be spotted.

♪♪ A giant hognose snake, over six feet long.

♪♪ Her only defense is to rock gently... ...to try to look like a leaf in the breeze.

♪♪ ♪♪ ♪♪ This snake is an egg eater.

♪♪ The chameleon needs to wait for the coast to be clear before she can start laying.

She's found the perfect spot.

♪♪ ♪♪ Her whole short life has been about getting to this moment... ♪♪ ♪♪ ...and her time has almost run out.

♪♪ ♪♪ With her last ounce of energy, she covers her eggs.

♪♪ Her life's journey is now complete.

♪♪ ♪♪ ♪♪ In her last moments, her skin erupts with color... ♪♪ ...as if uttering her last words.

♪♪ ♪♪ ♪♪ She is not the only one to have made such an incredible journey.

[ Fly buzzing ] Every chameleon of her species is now dead.

[ Fly buzzing ] All that remains are thousands of eggs, buried beneath the soil of Kirindy Forest... ...time capsules evolved to survive the deadly dry season... ...until they hatch, en-masse, when the wetter weather returns in seven months' time.

♪♪ Having found perfect habitat, the water vole is scent-marking the boundaries of her new territory... ...but she needs to mate within the next few days, to ensure any pups survive the winter.

300 feet from the burrow, she sniffs a distinctive odor.

A latrine.

[ Water vole sniffing ] There's a well-trodden path... ♪♪ ...and the chopped-up leftovers of a meal.

♪♪ ♪♪ ♪♪ At last, a male.

The voles here have lighter-colored fur... ...a sign that they have different ancestors.

♪♪ ♪♪ But attractiveness has little to do with fur color.

The most important thing to her is his fitness... ...crucial if her offspring are to inherit genes essential for survival in the highlands.

♪♪ ♪♪ A game of chase is a good test of his stamina.

♪♪ ♪♪ She leads him to her new burrow.

♪♪ Her journey is complete.

She's found a mate and a new life, eight miles from where she was born.

Three weeks later, and a new journey begins... ♪♪ ♪♪ ...motherhood.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ANNOUNCER: To learn more about what you've seen on this "Nature" program, visit pbs.org.

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