Original subtitles

This is a first for me.

I'm standing in the forests of Mexico

where every year 50 million butterflies assemble

to spend the winter together.

It's something I wanted to see ever since I first heard about it.

And this is just the first of 12 places I'm going to visit

in order to celebrate in this program some of the most spectacular sights

that the natural world has to offer.

A new Millennium and the biggest party the world has ever seen

As humans we traditionally punctuate our yearly cycle with mass gatherings

so too do many animals, coming together in huge numbers for a whole variety of reasons

Across the northern hemisphere

and the south, every month around our planet, nature throws its own massive parties

minus 6, 5, 4, 3, 2, 1

We have ignition and we have lift off and the shuttle has cleared the tower

Technology originally devised to help us see beyond our planet into space

is now of invaluable use in discovering more about our own home

Using the orbit of the shuttle as a guide,

we'll make a month by month journey around our planet

seeing how the sun and seasons influence nature's greatest spectacles

We begin in the northern hemisphere at the winter refuge of Monarch Butterflies

It seems extraordinary that during the secone half of the 20th century

when we were exploring space and men were walking on the moon,

the outside world knew nothing of this wonderful spectacle, it wasn't discovered until 1975

and then thankfully, immediately protected

But there are still a lot we don't know about the way in which these butterflies behave

but one thing is certain,

the trigger that sends us on these extraordinary journeys are the seasonal changes

that are brought about by the way our planet the earth rotates about the sun

Most great assemblers are driven by the search for food

or the eternal need to reproduce

For monarchs, it's a response to winter conditions further to the north

and someone have flown as far as 4000km to be here

Mass gatherings like this one are uncommon in the natural world

and as we shall see many are short-lived

Monarchs cluster together to keep warm,

for even here the days and nights can be cold

but on sunnier days, the dense clusters are in danger of overheating

Taking to the air helps them to cool down

and gives them an opportunity to exercise their wings

while monarchs may occasionally drink,

they will not feed much if at all during the winter

and with extreme cold persisting further to the north,

these butterflies will remain in this forest for several months

It's the far north that is home to our next spectacle

We journey to Newfoundland where both sea and land are frozen

Caribou are north America's long distance walkers,

spending their entire lives on the move

This far north the winter days are short

and the caribou use the daylight hours to search for food

This winter herd consists mainly of females and calves

They are part of the bigger George river herd, Canada's largest

which numbers an impressive half a million

When not moving, caribous spend much of the day with their heads buried in the snow

the males have lost their antlers but the females keep theirs throughout the winter

As mothers they need to be able to protect their excavations

for beneath the snow they find a lichen known as reindeer moss

which is rich in energy and the main winter diet for them and their calves

Unlike other deer, a caribou muscle is completely furred,

a necessary protection against frostbite

and their legs have a build-in arterial bypass that keeps heat in the upper body where its most needed

The herding instinct increases with the lengthening days

and the caribou become more purposeful in their travelling

This is the start of the great migration

as they prepare to leave their wintering grounds and journey towards the open tundra

As the George River herd moves northwards, and different strains come together,

winter loosens its grip, spring is approaching

On the other side of the northern hemisphere,

Japanese red crested cranes patiently sit out the last few days of winter

Japan's most northern island Hokkaido experiences the harsher side of winter

Unusually for cranes, they do not migrate despite temperatures of minus 20 degree Celsius

Instead they follow a traditional daily routine that brings them to regular feeding sites

Cranes live in communities throughout the winter

but like most animals in the northern hemisphere

the long awaited arrival of spring will cause a shift in the pattern of their daily schedule

By mid March a strengthening spring sun is enough to stir some activity and shake off the winter blues

but such early morning sessions provide only a hint of what is to become

For these cranes, the ritual of flying to feeding sites is no different in spring

Japanese cranes are heavy birds, males can weigh up to 15 kilos

Flying into the wind helps them to get airborne,

but with feeding sites just a few km from their roosts, they rarely fly higher than they need to

Display is central to the life of these birds

and the feeding grounds become the stages on which the Japanese cranes can do the thing they do best - dancing

Cranes form lifelong partnerships and dancing strengthens the bond between them

but it's also an opportunity for each pair to show off to the neighbors

While for the cranes the problems of winter are over,

another animal has had a very different winter experience

Like the cranes red-sided garter snakes patiently wait out the long winter,

but unlike cranes they do it underground

10 feet underground in fact

In all, they have spent 7 months beneath the Manitoban prairies

and their blood has congealed to the thickness of mayonaise

The males are the first to react to spring

and despite the remains of some winter snow, they emerge from deep underground

In a matter of days, they appear above the surface in their thousands

Under the warmth of an April sun,

the blackness of their stripes helps them to heat up more rapidly

Having spent so long underground, the males have lost a third of their body weight,

but before feeding they must mate

Their test-osterone levels are at an all-time low but this does not deter them

Sperm produced the previous summer has been stored in their bodies throughout the winter

and this is their one and only chance to use it

The females are 3 times the size of the males

but what the males lack in size, they make up for in number

It's not unusual for a single female to court more than 100 males

Attracted by the strong scent emitted by the females,

the snakes become embroiled in a sexual frenzy

The confusing massive bodies provides the opportunity for some males to cheat

They emit a scent identical to that of a female

and so draw other males away from the real females

As a result they can increase their chances of mating by as much as the third

Females are keen to leave the dens and feed on the open prairies

but heavily outnumbered they are often overpowered

Whatever the tactics of the males, the females will mate only once

For garter snakes, their annual sexual marathon is drawing to a close

With the long days of summer in full-swing across the northern hemisphere

one particular seabird ventures northwards from Africa and southern Europe

And there is one place it favors - Bass Rock, off Scotland's east coast

Gannets arrive in Britain from January onwards,

but their numbers build throughout the spring

For most of these birds this is familiar territory,

they would have made the same journey every year

Breeding couples are not only loyal to Bass Rock but to each other

and the gentle bout of bill fencing is their way of saying so

The number of gannets gathering on this tiny island has grown 5 fold in 30 years

by May, 70,000 birds cram tightly together

making this one of the largest gannet colonies in the world

It's little surprise therefore that some gannets have trouble locating the right nest

A male gannet establishes his nesting territory when he is 3 or 4 years old

From then onwards he and his partner will use the same nest site each year

A gannet nest is hardly an architectural wonder,

but home improvements will continue throughout the summer

Gannet chicks eat only a few times a day, but when they do, it's quite a feast

Their main diet is a mix bag of herring, mackerel and sand eels, served up with a dash of saliva

Keeping the feathers in good condition is an important routine for every bird

and gannets look after theirs with exquisite precision

Both male and female gannets go fishing and to ensure that a chick isn't left alone

one parent signals its intention to leave by pointing its bill skywards

Air traffic around Bass Rock reaches a peak as mid summer approaches

A diving gannet can hit the sea surface at a staggering 100km an hour

slicing through the water with a torpedolike velocity

The north sea provides rich rewards for these birds

and their fishing trips can last between 7 and 13 hours,

a direct benefit of the long summer days as they peak towards the summer solstice

In high summer, America's northernmost state stages a double spectacle

For salmon it's the once in their lifetime chance to breed

For grizzly bears, it's an unmissable midsummer feast

It takes a special event for the normally solitary and antisocial grizzlies to tolerate such a large gathering

And while there would always be the one that gets away

In a good year, a grizzly can eat some 30 kilos of salmon in a day

In poor salmon years, males will dominate the main fishing grounds,

females and cubs have to be content to fish on rivers away from the bigger males

Cubs born early in the summer discover how to fish by watching their mother

This yeanling has already learned to be more bold

Grizzly mothers don't feed their young directly, it's a case of grab what you can

Losing some food to an offspring is one thing,

but the smell of a fresh catch can attract bigger competition

Summertime it's better for a mother and her cubs to hang out in the relative safety of some tall grass

staying close to mom is an inbuilt mechanism for survival

Even so, fewer than half the cubs will make it to adulthood

Grizzlies are largely vegetarian, with less than a 3rd of their diet to be meat

Despite their baby teeth, spring cubs take to grazing early on

During summer, McNeil River Falls sees the biggest gathering of grizzlies in the world

and for bears that usually have home ranges of hundreds of square kilometers getting on with the neighbors can be difficult

The common hunger that draws some of the biggest of America's brown bears together could also produce some of the biggest fights

But they are for the most part tolerant of one another,

spending much of the day practising their varied styles of fishing

The basics are taught to the cubs by their mothers,

but as they get older, bears improve on these skills becoming more adept at catching fish with a minimum amount of effort

Large males weigh between 3 and 500k, the weight of 6 fully grown men

They can eat up to 15% of their body weight in a day

but if the runs are good, they become more selective often eating just the eggs

In a poorer salmon year, every bit is savored but not always by the bears

With their powerful front paws, keen vision and a good sense of smell,

some grizzlies become very expert indeed

But keeping a catch isn't always easy

Being in close company with other bears is certainly stressful

but the rewards it brings are great

and the bears need all the food they can get to carry them through their long and lonely winter hibernation

These river bears will stay together throughout the long days of summer

The Rift Valley lakes of east Africa are home to some 3 million lesser flamingos

It's the biggest gathering of any inland water bird in the world

and it's a wonder that can be seen throughout the year

for here on the equator, conditions are fairly constant

The volcanic forces that shape the landscape are never far away

Hot springs bubble constantly giving the birds their very own steam bath

The hot corrosive water at this caustic soda lake deters most animals

so flamingos have almost exclusive access to the microscopic blue-green algae it contains

They spend much of the time with their heads upside down filtering the algae from the distasteful water

Special airchambers in the bill provide extra buoyancy

so that they only sift the upper surface where the algae is most abundant

The water in the lake is too toxic to drink,

so every day the flamingos fly off to find something a little more palatable

The volcanic springs that feed the lake may not be the sweetest of the waters

but they are not caustic

With so many birds wanting to quench their thirst,

flamingos have to queue politely and wait their turn

They also have a much-needed opportunity to take a bath

and wash away the lake salts that coat their feathers

Flamingos are the most vulnerable when they are close to the lake edge

A fish eagle can only catch one if it's in shallow water

so many birds packed so closely together could easily panic

and exploiting that is the eagle's favorite technique

At times, the whole colony will join together to perform a ritualized dance

which may help them to synchronize their breeding

At the other end of the world, conditions couldn't be more extreme

While the northern hemisphere enjoys long summer days,

a winter blackout has descended across this frozen southern continent

the occasional burst of the aurora provides the only light

The winter temperatures have been dropping as low as minus 60 degree Celsius

and thousands of male emperor penguins have spent the last two months

huddled together in one great scrum

The first sign of seasonal change is the reappearance of the sun, a distant blip on the horizon

It seems perverse of these birds to decide that winter in Antarctic is the best time to bring up their young

The females are away fishing

and most of these males are carrying eggs on the top of their feet beneath a special fold of feathered skin

In ferocious winds of 200km/h the only practical way for them to keep warm is by huddling

It's a very democratic system, the penguins constantly move round the edge of the colony

ensuring that each gets a reasonable time in the lee of the huddle away from the wind

By August, the warmer temperatures allow the colony to break up

Winter has taken its toll and the males have lost half their body weight

They're also left holding the baby

These newly hatched chicks can expert very little from their fathers

After four months of fasting, there is nothing solid in a male's stomach

but he is able to produce a protein rich secretion

but that is barely enough to keep a chick alive for a week

Fattened up from 2 months' fishing the females reappear with magically accurate timing

In such a crowd, calling is the best way to locate her partner

A female arrives to take over

at first, the male is a little reluctant to abandon his offspring

Once the exchange starts, it needs to be quick

a few minutes on the ice would almost certainly kill the chick

Now at last, the chick can feed properly

During the next 5 months, an emperor chick would eat 100k of food

In one big helping, it can eat 1/3 of its own body weight

Now at last, their fathers have a chance to eat

but the ice edge may be several hundred kilometers away

Emperor penguins have a fast mode of transport than just plain walking,

they can toboggan

From now on, males and females will take turns to go fishing

Each trip may involve travelling thousands of kilometers in search of food

With spring now well established in the southern hemisphere

one of the world's smaller dolphins makes an entrance

Dusky dolphins live permanently around the coasts of New Zealand

but at this time of year, they gather off the south island in pods hundred strong

And being a dusky dolphin requires a certain acrobatic flair

Why these dolphins leap is still uncertain,

but males are known to chase females in an airborne courtship

and spring is the beginning of the mating season

Leaping may also be a technique used by the pods to herd fish

The splashes of the dolphins at the front of the pod could well signal to others the location of fish

and may push their prey towards the dolphins in the middle

Whatever the reason, duskies are without doubt highly cooperative and social animals

Some of the big pods number 500

and reach their peak during the southern hemisphere's spring and summer

Gathering in such numbers,

seems to stimulate the dolphins to perform their most dazzling acrobatics

Still in the southern hemisphere just south of the equator,

one of nature's greatest shows is taking place

Nearly 2 million wildebeest,

this journey is the biggest land mammal migration on our planet

They're driven to cross every obstacle and the Mara river is the most perilous

It's the promise of rain that starts them on their cyclical journey

and wildebeest noses can detect rainfall 30km away

The sight and smell of the Mara river seems to panic the wildebeest

and the resulting crush becomes more hazardous

Wildebeest like many grazing animals find safety in numbers

but big numbers nonetheless attract attention

This is one of the few occasions when crocodiles work as a team

It can sometimes take more than one pair of jaws to overpower a wildebeest

A river crossing may last several days

and the vast majority of wildebeest will make it successful

Inevitably though some will be luckier than others

And this is why they do it

the shifting rains have brought fresh growth to the pastures of the Serengeti

the new grass will support the herds for the next 6 months

then once again, new rains in the north will bring them back full circle

Across the Indian Ocean, and almost on the same latitude as the Serengeti

Christmas Island has now experienced the first rains of its monsoon

The humid conditions are a trigger for the emergence of this island's most common resident, the red crab

November is the start of a mass migration for these land crabs

The males leave their burrows first

and within a few days there are spectacular numbers of them out in the open

This is just the first wave of a migration that will ultimately involve some 80 million crabs

Soon they spill out of the forests into human territory

Road traffic is one of their biggest hazards

The crabs follow migratory paths that run in almost straight lines

and they take no account of oncoming traffic

Their destination is the sea

and after a couple of weeks travelling, the male crabs head straight for the water

Red crabs lost their sea legs long ago in evolution

and so now they are in danger of drowning

the water in a rock pool is the safest way of getting a drink

Salts lost on the journey are recovered by a quick dabble in the surf

Soon after they arrive, the male crabs leave the beach and make new burrows in the forest above the coast

With the arrival of the females the whole reason for their journey becomes apparent

Red crabs may live on land, but their reproduction is tied to the sea

Once mated, the female takes over the burrow

and remains there for two weeks incubating her eggs in a specialized pouch

When she emerges, she joins other females each carrying around 100,000 eggs

This final stage of the journey from the coastal forest to the sea

is the equivalent in human term of a person carrying a 7-kilo-load for over 30km

From the outset the red crab migration is operated with military precision

It culminates in millions of expectant mothers reaching the sea on the eve of the highest tide

While some crabs will attempt to release their eggs from the cliffs,

most take the final few steps to the sea edge

For some, this is their first time

but for others, it's a familiar experience

Red crabs can live for as long as 20 years

This is a dangerous time for them since they are poor swimmers

many will drown but the urge to release their eggs is overwhelming

Each wave surging up the beach, stimulates the crabs to release their eggs

and the retreating water turns brown

Hopping up and down helps empty the egg pouches

The young hatchlings will remain in the sea for 3 weeks and then return to land

but only a tiny fraction will survive to do so

Another generation is spawned ensuring that Christmas Island will remain the island of red crabs

The last stage of our global journey takes us to the Great Barrier Reef

the first structure built by living organisms to be identified from space

It stretches over 2000km and is home to 400 different types of coral

It's the largest living structure in the world

But the real magic of this spectacle isn't in the size of the reef or the numbers of the animals it supports

Now in mid-December the summer solstice is approaching in southern hemisphere

for each and every coral their one chance to reproduce is about to arrive

Water temperature and the lunar cycle act as triggers

For several days after a full moon,

the corals synchronize the release of their eggs and sperm into the ocean

Individual corals of the same species spawn together,

their timing is precise to the hour

The full secrets of the reef's spectacular sex life were not discovered until 12 years ago

a reminder that we still have much to learn about our planet

As the spawning reaches its climax, billions of eggs and sperm are cast adrift

it's as if nature is throwing its own firework party

Great mass spectacles are rare in nature

many are ephemeral lasting only a matter of days or weeks

Today we are perhaps more aware of their fragility

the last Millennium may have been an age of discovery

but it was also one of loss

200 years ago, the wilderness of north America was home to a sight that stunned the pioneering settlers

60 million bison roamed the vast expanses of the American prairies

They must have seen so numerous as to be indestructible,

but within less than a century, their numbers were reduced to just 600

We may have lost the spectacle, but we still have the species

I'm in the first of all national parks Yellowstone in the United States

and here carefully protected a handful of bison have increased to several thousand

It's true that in the past century we've been inflicted terrible damage on the earth

but thanks to the work of conservationists,

there is still a great deal to celebrate on this planet

long may remain, so Happy New Millennium

Subtitles by Andrew and Hattie www.mvgroup.org