0:00:04 > 0:00:08Every year, spectacular seasons transform our planet.
0:00:10 > 0:00:14They are the driving force of all life on Earth.
0:00:16 > 0:00:20Bringing opportunities and huge challenges.
0:00:23 > 0:00:25Spring bursts with new life.
0:00:27 > 0:00:30But it's a race to grab fleeting chances.
0:00:32 > 0:00:34Summer is all about glorious abundance.
0:00:36 > 0:00:38But the heat can push animals to their limits.
0:00:40 > 0:00:43Autumn is nature's great gold rush.
0:00:47 > 0:00:49But competition is fierce.
0:00:52 > 0:00:55Winter creates a frozen wonderland...
0:00:57 > 0:00:59..and only the most resourceful will survive.
0:01:08 > 0:01:10In every corner of the planet,
0:01:10 > 0:01:13animals rise to overcome the seemingly impossible...
0:01:15 > 0:01:17..and use extraordinary tricks...
0:01:18 > 0:01:20..to thrive against the odds...
0:01:21 > 0:01:25..as the seasons create the greatest shows on earth.
0:01:36 > 0:01:38Summer.
0:01:38 > 0:01:43The flowers are blooming, the sun is shining, the days are long.
0:01:43 > 0:01:46But the living isn't always easy.
0:01:47 > 0:01:52These sweltering days have their challenges.
0:01:52 > 0:01:54The competition for summer's bounty
0:01:54 > 0:01:57can push every creature to its limits.
0:02:00 > 0:02:05So the first challenge is making sure you grab your share.
0:02:20 > 0:02:23Across the world, nature is at its most lavish.
0:02:24 > 0:02:28For insects, the explosion of flowers creates a banquet.
0:02:34 > 0:02:37The more the sun warms the flowers,
0:02:37 > 0:02:39the more nectar they produce.
0:02:43 > 0:02:46For a little honeybee, these are busy times.
0:02:50 > 0:02:52Every working bee is a female.
0:02:53 > 0:02:57Between them, they'll visit 2 million flowers
0:02:57 > 0:03:01to collect enough nectar to make just one cupful of honey.
0:03:05 > 0:03:07In a woodland in Minnesota,
0:03:07 > 0:03:10this colony of 40,000 honeybees is hard at work.
0:03:17 > 0:03:20Summer's honey will be stored away to keep them going over winter.
0:03:24 > 0:03:29Each bee might only make a 12th of a teaspoon of honey in her whole life.
0:03:30 > 0:03:32She won't give it up lightly.
0:03:34 > 0:03:35But they're being watched.
0:03:38 > 0:03:40A black bear cub.
0:03:42 > 0:03:44He needs to more than double his weight over summer
0:03:44 > 0:03:47to survive a five-month winter hibernation.
0:03:49 > 0:03:52A mouthful of honey and bee grubs is packed with calories.
0:03:56 > 0:03:59But there's a technique to getting it and he hasn't learnt it.
0:04:01 > 0:04:03He's soon surrounded by angry bees...
0:04:05 > 0:04:06..and is way out of his depth.
0:04:13 > 0:04:16Fortunately, his mother is an expert.
0:04:26 > 0:04:28The stings are ferocious
0:04:28 > 0:04:32but her fur is so thick she simply shakes the bees off.
0:04:33 > 0:04:35But her bare face is more vulnerable.
0:04:37 > 0:04:39She can stand the attack just long enough to grab a honeycomb.
0:04:46 > 0:04:49For the bears, this is a valuable meal.
0:04:51 > 0:04:54They must take any chance they can to fatten up during summer.
0:04:56 > 0:05:01They're mostly vegetarian, but right now they'll eat anything.
0:05:01 > 0:05:06Bees, grubs, honeycomb, the lot.
0:05:16 > 0:05:18It might look like a disaster for the bees...
0:05:23 > 0:05:25..but all is not quite lost.
0:05:28 > 0:05:31Each bee will eat her own weight in the remaining honey
0:05:31 > 0:05:34to keep her going while they rebuild their home.
0:05:42 > 0:05:46Summer is full of golden opportunities
0:05:46 > 0:05:48but you have to grab them while you can...
0:05:49 > 0:05:52..because some of them are truly fleeting.
0:05:57 > 0:05:59The Canadian Rockies.
0:06:00 > 0:06:04In these northern mountains, summer doesn't last long.
0:06:04 > 0:06:07It's only August, but it could be snowing by September.
0:06:09 > 0:06:12So flowers rush to bloom while it's still warm.
0:06:16 > 0:06:18But someone is picking them.
0:06:25 > 0:06:26A pika.
0:06:29 > 0:06:32She's the miniature cousin of a rabbit.
0:06:32 > 0:06:35And she's doing something that no other animal does.
0:06:35 > 0:06:38She's building a haystack.
0:06:43 > 0:06:46In winter, her home could be under half a metre of snow...
0:06:48 > 0:06:51..so she's creating a makeshift larder
0:06:51 > 0:06:54so she can dine on flowers during the long winter months.
0:07:02 > 0:07:04She really is making hay while the sun shines.
0:07:06 > 0:07:08She's very choosy.
0:07:08 > 0:07:12She'll only pick what's in season when it's at its most nutritious.
0:07:14 > 0:07:16She eats some and stores some
0:07:16 > 0:07:19and she even adds some toxic plants to the hoard.
0:07:19 > 0:07:22They'll act as a natural preservative over winter.
0:07:26 > 0:07:28Over these few weeks of summer,
0:07:28 > 0:07:32she might make 14,000 trips down to the flower meadows.
0:07:39 > 0:07:42But it's a slog going up and down the mountainside.
0:07:45 > 0:07:48Maybe there's an easier way.
0:07:49 > 0:07:55A neighbouring pika has started building his own haystack just down the slope.
0:08:00 > 0:08:03As soon as his back is turned,
0:08:03 > 0:08:06his devious little neighbour helps herself.
0:08:17 > 0:08:19The rightful owner comes back
0:08:19 > 0:08:21just in time to see his precious winter supplies
0:08:21 > 0:08:22disappearing round the corner.
0:08:25 > 0:08:27And he is furious.
0:08:27 > 0:08:30MR PIKA SQUEAKS
0:08:37 > 0:08:39Thieving is rife around here in summer...
0:08:42 > 0:08:45..and every pika has to be constantly on guard.
0:08:47 > 0:08:50But it's not just other pikas you have to watch.
0:09:04 > 0:09:07The bighorn sheep know an easy meal when they see one.
0:09:16 > 0:09:21Without her vital supplies, she won't survive the Canadian winter,
0:09:21 > 0:09:23so it's straight back to work to get some more.
0:09:25 > 0:09:28Summer might be a time of abundance, but with such competition...
0:09:29 > 0:09:32..it pays to be a little bit cunning.
0:09:33 > 0:09:36And in the forests of southern Madagascar,
0:09:36 > 0:09:39one animal has come up with an ingenious strategy.
0:09:40 > 0:09:41A ring-tailed lemur.
0:09:46 > 0:09:49All around, the trees are full of huge bugs.
0:09:49 > 0:09:53They're cicadas, and in the summer rainy season they're out in force.
0:09:56 > 0:09:59They drink the tree sap, extract the sugar...
0:10:01 > 0:10:04..and then excrete great jets of honeydew.
0:10:11 > 0:10:14And for the lemurs, that is a sign to start hunting.
0:10:17 > 0:10:22These fat little insects are rich in protein - a lemur's summer treat.
0:10:25 > 0:10:26But there's a problem.
0:10:29 > 0:10:33Cicadas fly and they're pretty hard to catch.
0:10:50 > 0:10:52The effort can outweigh the reward.
0:10:59 > 0:11:00But there is an easier way.
0:11:02 > 0:11:03A giant wasp.
0:11:06 > 0:11:08A specialist in hunting cicadas.
0:11:11 > 0:11:13She paralyses it with her sting
0:11:13 > 0:11:16and then drags it to her underground larder.
0:11:25 > 0:11:28All the lemur has to do is watch where the wasp hides it...
0:11:31 > 0:11:33..and then go and dig it up.
0:11:39 > 0:11:43A treat like this is only available for a short time...
0:11:45 > 0:11:47..and it tastes so much sweeter
0:11:47 > 0:11:49when someone else does the hard work for you.
0:11:54 > 0:11:57Summer feasts are often fleeting
0:11:57 > 0:12:02and sometimes making the most of them requires not just cleverness but sheer bravery.
0:12:04 > 0:12:09On the Serengeti in Eastern Africa, a massive herd is on the move,
0:12:09 > 0:12:12following the arrival of lush summer grass.
0:12:16 > 0:12:20A million wildebeest, zebra and antelope.
0:12:28 > 0:12:31And all these animals attract flies.
0:12:32 > 0:12:33Billions of them.
0:12:40 > 0:12:42For a rainbow lizard, this could be paradise.
0:12:45 > 0:12:49While the herds are around, the air will be full of flying food.
0:12:56 > 0:12:59All the lizard has to do is grab the flies with his sticky tongue.
0:13:05 > 0:13:06But it's not as easy as it looks.
0:13:21 > 0:13:24There might be a simpler way to catch them.
0:13:26 > 0:13:28If you're brave enough.
0:13:30 > 0:13:33Because it's not just wildebeest that attract flies.
0:13:39 > 0:13:43But how can you possibly get close enough to reach them?
0:13:50 > 0:13:54Lions are the world's least active big cats.
0:13:55 > 0:14:00They rest for a good 18 hours a day, so there's plenty of opportunity.
0:14:01 > 0:14:03But you need to hold your nerve.
0:14:09 > 0:14:14The brighter, more dominant blizzard should take the lead
0:14:14 > 0:14:18but, while he's still thinking about it,
0:14:18 > 0:14:20a smaller lizard seizes the moment.
0:14:48 > 0:14:51Lions can be testy.
0:14:51 > 0:14:54They're not likely to eat the lizards,
0:14:54 > 0:14:56but one swipe with a paw that size
0:14:56 > 0:14:57and it would be game over.
0:15:01 > 0:15:03So you need to choose your moment.
0:15:13 > 0:15:14Got one.
0:15:21 > 0:15:23The lizards start to up the ante.
0:15:35 > 0:15:37The secret is to move fast
0:15:37 > 0:15:39and to know when to stop.
0:15:44 > 0:15:46When times are this good and there's plenty of food,
0:15:46 > 0:15:49some animals turn their thoughts to starting a family.
0:15:51 > 0:15:55These long days of summer are the perfect time to look for a mate.
0:15:57 > 0:15:59But that brings challenges of its own.
0:16:10 > 0:16:13For some, it's a time to get back together with an old flame.
0:16:19 > 0:16:22On Heron Island in northern Australia,
0:16:22 > 0:16:25a pair of noddy terns sit and bob their heads,
0:16:25 > 0:16:28getting to know each other again after a few months apart.
0:16:30 > 0:16:34The warm days of high summer are the time to raise a family but it's good
0:16:34 > 0:16:37to take a moment to get reacquainted.
0:16:40 > 0:16:43On the Great Barrier Reef, the rising warmth of the water
0:16:43 > 0:16:47is the cue to get a parrotfish couple in the mood.
0:16:51 > 0:16:53The male takes the lead,
0:16:53 > 0:16:56gently brushing her fins as he dances around her.
0:17:02 > 0:17:06But, for a crowd of surgeon fish, it's just one big party.
0:17:08 > 0:17:12The females rise to the surface and release their eggs
0:17:12 > 0:17:16and the males dash to be the first to fertilise them with a puff of sperm.
0:17:22 > 0:17:24Summer is a time to flaunt yourself.
0:17:25 > 0:17:28You're never going to find a partner if you hide yourself away.
0:17:33 > 0:17:36But there's one animal that lives in such a hidden place
0:17:36 > 0:17:40its astonishing summer courtship has only just been discovered
0:17:40 > 0:17:41by the outside world.
0:17:45 > 0:17:50In the isolated forests of Mount Mabu in Mozambique,
0:17:50 > 0:17:52butterflies are emerging after the summer rains.
0:18:03 > 0:18:07As soon as their wings dry, they will set out in search of a mate.
0:18:16 > 0:18:20Hundreds of thousands of butterflies are ready to breed
0:18:20 > 0:18:23but they won't find their perfect partner in a forest this dense.
0:18:25 > 0:18:26Their only option...
0:18:28 > 0:18:30..is to head for the open air.
0:18:34 > 0:18:36They follow rivers upstream,
0:18:36 > 0:18:39travelling higher and higher up the mountain.
0:18:43 > 0:18:44It can take hours.
0:18:48 > 0:18:50But finally they break out into the light.
0:18:58 > 0:19:00They've reached a treeless mountaintop,
0:19:00 > 0:19:02the only open space around.
0:19:02 > 0:19:04Now the fun can begin.
0:19:22 > 0:19:27The males must show off their flying strength to win a female
0:19:27 > 0:19:28and fight off rivals.
0:19:31 > 0:19:34They only have about an hour each day when conditions are just right.
0:19:41 > 0:19:43Finally, they'll return to the depths of the forest
0:19:43 > 0:19:45and the females will lay their eggs.
0:19:49 > 0:19:52But they've had their moment in the sun.
0:20:07 > 0:20:11For some animals, pairing up is a much less gentle affair.
0:20:13 > 0:20:15In the deserts of the Middle East,
0:20:15 > 0:20:17it's all about strength and endurance.
0:20:18 > 0:20:23For a male Nubian ibex, courtship is highly competitive.
0:20:25 > 0:20:30It's late summer. On these barren slopes in eastern Israel,
0:20:30 > 0:20:32life is tough at the best of times.
0:20:33 > 0:20:36As the temperatures soar, it's about to get tougher.
0:20:37 > 0:20:42The females need to give birth in spring, so they must mate soon.
0:20:42 > 0:20:44And the males know it.
0:20:46 > 0:20:50For most of the year these big males live quiet lives...
0:20:50 > 0:20:51but not now.
0:20:55 > 0:20:57For weeks these males will hardly eat.
0:20:58 > 0:21:02They won't do much at all except try to beat each other up.
0:21:15 > 0:21:18The toughest ibex gets all the females,
0:21:18 > 0:21:20so it's all about the fight.
0:21:31 > 0:21:33These are young bucks, evenly matched.
0:21:34 > 0:21:37They can go on like this for an hour or more.
0:21:59 > 0:22:01But neither of these is going to win.
0:22:01 > 0:22:06The females only have eyes for this strong, experienced male,
0:22:06 > 0:22:08with his enormous horns.
0:22:15 > 0:22:17The younger males never had a chance.
0:22:18 > 0:22:20For now they can only practise.
0:22:27 > 0:22:32But, eventually, one of them will fight his way to become the next champion male.
0:22:38 > 0:22:42For one animal, summer courtship is an even more spectacular event.
0:22:42 > 0:22:45But success is all about timing.
0:22:47 > 0:22:51On Christmas Island in the Indian Ocean summer brings
0:22:51 > 0:22:55what is probably the most dramatic mass emergence in the world.
0:23:00 > 0:23:01Christmas Island crabs.
0:23:03 > 0:23:07They've spent months hiding away in the forest, all alone.
0:23:07 > 0:23:11It's only now, in the rainy days of a tropical summer,
0:23:11 > 0:23:12that they venture out.
0:23:15 > 0:23:18They need moisture in the air or they'll dry out.
0:23:18 > 0:23:23So when the humidity is over 85%, out they come.
0:23:28 > 0:23:31There may be more than 40 million of them
0:23:31 > 0:23:33and they're heading straight for the beach.
0:23:37 > 0:23:39It can take them a week to get there...
0:23:41 > 0:23:45..but their hormones kick-start a sugar rush in their bodies
0:23:45 > 0:23:49and, after months of inactivity,
0:23:49 > 0:23:52they're now dashing along at 300 metres an hour.
0:24:00 > 0:24:02At the coast, they pair up.
0:24:08 > 0:24:11Once they've mated, each female needs to get her eggs into the water.
0:24:18 > 0:24:21As night falls on the high tide, the final push starts.
0:24:27 > 0:24:29Their babies need to start their lives in the sea.
0:24:31 > 0:24:35But there's a problem. These mothers can't swim.
0:24:35 > 0:24:38If they get washed away, they drown.
0:24:39 > 0:24:43So they paddle into the shallows and shimmy out their eggs from there.
0:24:53 > 0:24:56Then it's the long walk back to the safety of the forest.
0:24:56 > 0:24:58To wait for next summer's rains.
0:25:01 > 0:25:03After just a few frantic weeks,
0:25:03 > 0:25:0740 million crabs simply vanish among the trees.
0:25:07 > 0:25:11One of the world's most epic breeding events is all over for another year.
0:25:19 > 0:25:22The summer sun gives life a burst of energy.
0:25:26 > 0:25:30But when it's highest in the sky, it also brings roasting heat.
0:25:33 > 0:25:38So the next challenge summer throws out is keeping your cool.
0:25:45 > 0:25:47So how do you keep the temperature down?
0:25:52 > 0:25:55Lions can overheat in the hottest part of the day.
0:25:58 > 0:26:00So they sleep through it,
0:26:00 > 0:26:03turning their bellies to the air to catch a cooling breeze.
0:26:08 > 0:26:13In the Australian Outback, where temperatures can hit 50 degrees,
0:26:13 > 0:26:15red kangaroos lick their arms.
0:26:18 > 0:26:21The saliva cools them, just like sweat does.
0:26:24 > 0:26:28Koalas hug trees to stay chilled.
0:26:28 > 0:26:31Trees stay cooler in the summer
0:26:31 > 0:26:34and a koala can avoid overheating
0:26:34 > 0:26:36just by lying up against one.
0:26:40 > 0:26:44In a drying Zambian river a hippo wallows in mud
0:26:44 > 0:26:47to keep cool while it's waiting for a summer rains.
0:26:48 > 0:26:54But it also sweats out a unique red liquid that acts as sun cream.
0:27:05 > 0:27:10But when it comes to sheer heat, deserts break all records.
0:27:19 > 0:27:23To live in these superheated places you have to be built for it.
0:27:32 > 0:27:34Daybreak in the Arabian desert
0:27:34 > 0:27:37and a dabb lizard is using the sun's warmth
0:27:37 > 0:27:39to warm up after a chilly night.
0:27:41 > 0:27:44At this time of day his scales are black to absorb most heat.
0:27:48 > 0:27:51But as the temperature rises he starts to overheat.
0:27:57 > 0:28:00And he undergoes a remarkable transformation.
0:28:01 > 0:28:03The dark pigment in his skin
0:28:03 > 0:28:07gets gradually paler to reflect the sun's heat.
0:28:11 > 0:28:13After a few minutes,
0:28:13 > 0:28:18he can finally saunter off a completely different colour.
0:28:20 > 0:28:23And totally chilled.
0:28:33 > 0:28:37But there are some desert animals that face an even tougher summer.
0:28:37 > 0:28:39The Sahara Desert.
0:28:39 > 0:28:42This is one of the hottest places on earth.
0:28:42 > 0:28:46Summer temperatures can reach nearly 60 degrees centigrade.
0:28:58 > 0:29:02But in this sweltering place there are the ultimate desert survivors.
0:29:08 > 0:29:12These are silver ants - the toughest on Earth.
0:29:21 > 0:29:23They're built for life in this natural furnace.
0:29:25 > 0:29:29Their extra-long legs raise their bodies off the hot sand
0:29:29 > 0:29:32and, when they run, they're the fastest ants on earth.
0:29:35 > 0:29:38But their secret weapon is their hairy bodies.
0:29:40 > 0:29:44New science has revealed that these hairs are shaped like tiny prisms.
0:29:44 > 0:29:48Perfectly reflecting the sun and stopping the ants overheating.
0:29:55 > 0:29:57Being the world's only hairy ant
0:29:57 > 0:30:00means they can stay busy clearing sand
0:30:00 > 0:30:05and looking for food in the full glare of the roasting midday sun.
0:30:09 > 0:30:12They spin round, taking bearings from the sun
0:30:12 > 0:30:15so they don't get lost in the burning desert.
0:30:20 > 0:30:23Other insects aren't nearly so tough.
0:30:23 > 0:30:25This fly has keeled over.
0:30:26 > 0:30:28And that's what these ants are looking for.
0:30:30 > 0:30:33It means they can feast on easy victims
0:30:33 > 0:30:35and stay safe from attack themselves.
0:30:37 > 0:30:40No other predators could cope with this sort of heat.
0:30:47 > 0:30:50But even silver ants have their limits.
0:30:50 > 0:30:56If their bodies go above precisely 53.6 degrees, they will die.
0:30:56 > 0:30:59They can only stay out in the sun for ten minutes.
0:30:59 > 0:31:03And they're running out of time.
0:31:04 > 0:31:06Some are already expiring.
0:31:12 > 0:31:16They need to get back underground... fast.
0:31:33 > 0:31:34Just in time.
0:31:39 > 0:31:43But you don't need to live in the desert to feel the heat of high summer.
0:31:48 > 0:31:50Even when you get down towards Antarctica,
0:31:50 > 0:31:54the coldest place on the planet, you can still overheat.
0:31:57 > 0:32:01It's the middle of a long breeding season for king penguins
0:32:01 > 0:32:05and on the island of South Georgia in the South Atlantic Ocean
0:32:05 > 0:32:08400,000 gasping birds are crowded together.
0:32:16 > 0:32:18It's one enormous creche.
0:32:27 > 0:32:31In midsummer, temperatures can hit a balmy 17 degrees.
0:32:35 > 0:32:38And the penguins are feeling it.
0:32:39 > 0:32:43The dense coat of feathers that keeps them warm in the sub-Antarctic winter
0:32:43 > 0:32:45is far too hot for the height of summer.
0:32:51 > 0:32:52Everyone is sweltering.
0:32:58 > 0:33:00Even the neighbouring elephant seals
0:33:00 > 0:33:03are throwing wet sand over themselves to cool off.
0:33:11 > 0:33:15The adult penguins can head off to fish in the refreshing South Atlantic.
0:33:54 > 0:33:57But the chicks still have their downy winter overcoat.
0:34:04 > 0:34:08They can lose some heat through their enormous feet
0:34:08 > 0:34:10but not enough.
0:34:13 > 0:34:16These chicks take more than a year to fledge
0:34:16 > 0:34:19and it'll be another two months before they can swim properly.
0:34:23 > 0:34:26So they take a tentative dip in a chilly glacier stream.
0:34:40 > 0:34:43But it's a bit choppy and it's hard to stay on your feet.
0:34:53 > 0:34:54So they find an alternative.
0:34:56 > 0:34:59A muddy pool, just cool enough to be refreshing.
0:35:47 > 0:35:49Now THAT was fun!
0:35:54 > 0:35:58When the heat builds, keeping cool is a challenge for everything.
0:35:59 > 0:36:02But the burning sun doesn't just overheat animals.
0:36:04 > 0:36:06It also draws the water from the land.
0:36:10 > 0:36:13And when your world is in danger of drying out
0:36:13 > 0:36:15it brings a whole new set of challenges.
0:36:25 > 0:36:28This is Namibia in southern Africa.
0:36:30 > 0:36:32It's getting late in the dry season.
0:36:34 > 0:36:38The increasing heat will bring tropical summer thunderstorms
0:36:38 > 0:36:40but there's no sign of rain yet.
0:36:49 > 0:36:53Then suddenly, out of nowhere, there's life.
0:36:55 > 0:36:57Crowds appear as if by magic.
0:37:00 > 0:37:02But there seems to be nothing for them.
0:37:28 > 0:37:32They're here because there's an ancient underground spring.
0:37:36 > 0:37:39Even when everything has turned to dust,
0:37:39 > 0:37:42it bubbles to the surface and never runs completely dry.
0:37:48 > 0:37:53At this time of year, when everything is waiting for summer rains,
0:37:53 > 0:37:54it's like the promised land.
0:38:03 > 0:38:07Every day hundreds of animals gather from miles around,
0:38:07 > 0:38:11all jostling together for this precious chance of a drink.
0:38:12 > 0:38:14It's like the world's most exotic bar.
0:38:22 > 0:38:25But with all these animals crowded together,
0:38:25 > 0:38:27it brings dangerous attention.
0:38:32 > 0:38:33Lions.
0:38:43 > 0:38:45The herds are spooked.
0:39:15 > 0:39:18But all the lion wants right now is a drink.
0:39:20 > 0:39:23And nobody is going to stand in her way.
0:39:29 > 0:39:34The shortage of water means predators and prey must all drink alongside each other.
0:39:38 > 0:39:44When the summer rains finally fall there will be plenty of water and the crowds will vanish.
0:39:46 > 0:39:49But, for now, this is a life-saver.
0:40:01 > 0:40:03Just when everything seems bone dry,
0:40:03 > 0:40:07refreshment can come from the most unlikely places.
0:40:11 > 0:40:15In the Sonoran Desert of Arizona and New Mexico,
0:40:15 > 0:40:17it might not rain at all for five months.
0:40:20 > 0:40:25But this saguaro cactus took precautions long ago.
0:40:34 > 0:40:37These giants only live in this one desert,
0:40:37 > 0:40:40and they're totally tuned in to its seasons.
0:40:43 > 0:40:45Last time it rained,
0:40:45 > 0:40:49this giant among cacti sucked up the sudden flood of water
0:40:49 > 0:40:51and its pleated trunk expanded like a concertina.
0:40:55 > 0:40:57Its main roots are shallow,
0:40:57 > 0:41:01but they spread out 30 metres all around its base.
0:41:04 > 0:41:08Its trunk is so huge it could have five tonnes of water
0:41:08 > 0:41:10packed away inside.
0:41:10 > 0:41:12It not only survives...
0:41:13 > 0:41:14..it thrives.
0:41:19 > 0:41:23As the weeks go on and the drought tightens, it flowers.
0:41:28 > 0:41:30And then at the height of summer,
0:41:30 > 0:41:34with its carefully gathered store of water,
0:41:34 > 0:41:36it produces the most luscious fruit.
0:41:38 > 0:41:41In the desert, that makes it a lifeline.
0:41:43 > 0:41:46There are visitors from far and wide.
0:41:46 > 0:41:50There may be 60 different types of animal reliant on its generosity.
0:41:50 > 0:41:51Birds,
0:41:51 > 0:41:53insects...
0:41:56 > 0:41:58..even desert tortoises rush to the feast.
0:42:00 > 0:42:03And just when the fruit is running out,
0:42:03 > 0:42:05the heat of high summer brings a sudden change.
0:42:08 > 0:42:10Thunderstorms.
0:42:10 > 0:42:11North America's summer monsoon.
0:42:13 > 0:42:15THUNDER CLAPS
0:42:20 > 0:42:23The cactuses get to replenish their reserves.
0:42:26 > 0:42:28To survive summer's toughest times,
0:42:28 > 0:42:31sometimes you just have to wait for it to change.
0:42:32 > 0:42:35But sometimes you have to go and get what you need.
0:42:37 > 0:42:40To find summer's greatest riches
0:42:40 > 0:42:43some animals will travel thousands of miles.
0:42:43 > 0:42:46Literally, to the ends of the Earth.
0:42:54 > 0:42:59Millions of sooty shearwaters fly all the way from New Zealand
0:42:59 > 0:43:01to raise their babies in Alaska.
0:43:03 > 0:43:06Just because the summer seas are full of fish.
0:43:09 > 0:43:13Humpback whales swim more than 3,000 miles from Hawaii
0:43:13 > 0:43:17to spend summer in the same rich Alaskan waters.
0:43:18 > 0:43:21It's the longest mammal migration on Earth.
0:43:23 > 0:43:24But it's not just the big animals
0:43:24 > 0:43:27that make the most adventurous trips.
0:43:30 > 0:43:33This is the smallest migrating bird in the world.
0:43:35 > 0:43:37A calliope hummingbird.
0:43:42 > 0:43:44His wings are only four centimetres long
0:43:44 > 0:43:46and he weighs less than a penny.
0:43:50 > 0:43:53But he's just flown 3,000 miles to get here.
0:43:58 > 0:44:00He's come all the way up from Mexico
0:44:00 > 0:44:02to the mountains of Wyoming.
0:44:03 > 0:44:05Just for the flowers!
0:44:08 > 0:44:10Here in North America, there are richer pickings
0:44:10 > 0:44:13than back at home in the heat of Mexico.
0:44:13 > 0:44:17Here, he can drink his own weight in nectar every day.
0:44:25 > 0:44:28But this is a popular summer destination for hummingbirds.
0:44:30 > 0:44:34You have to be prepared to fight for your flower patch.
0:44:36 > 0:44:39A rufous hummingbird is twice his size,
0:44:39 > 0:44:42but the calliope male is feisty.
0:44:42 > 0:44:44He's not going to let anyone muscle in.
0:44:55 > 0:44:58The summer bounty is so good here
0:44:58 > 0:45:01it's where the hummingbirds choose to raise their little ones.
0:45:01 > 0:45:04And they don't get much littler than this.
0:45:06 > 0:45:09The nest is barely the size of an egg cup.
0:45:10 > 0:45:13The babies are already bursting out of it.
0:45:15 > 0:45:18Their father doesn't get involved in childcare.
0:45:19 > 0:45:22It's down to their mother to get them fed,
0:45:22 > 0:45:25pumping a mixture of nectar and insects
0:45:25 > 0:45:26straight from her beak into their throats.
0:45:33 > 0:45:35But she's in a hurry.
0:45:37 > 0:45:42In about three weeks, she will be off back to Mexico for the winter.
0:45:42 > 0:45:44The chicks will fledge soon,
0:45:44 > 0:45:47but neither parent will wait for them.
0:45:48 > 0:45:52These young hummingbirds will have to find their own way back to Mexico
0:45:52 > 0:45:53all by themselves.
0:45:53 > 0:45:57Nearly 3,000 miles on almost nothing but nectar.
0:45:58 > 0:46:00That's quite a start to life.
0:46:06 > 0:46:10But that's nothing compared with the long haul flight made by this Arctic tern.
0:46:13 > 0:46:17It's the longest migration of any animal on Earth.
0:46:20 > 0:46:23He's flown all the way from Antarctica
0:46:23 > 0:46:27and he'll spend the summer here in Svalbard, in the Arctic -
0:46:27 > 0:46:32a 44,000 mile round trip,
0:46:32 > 0:46:35from the bottom of the planet to the top.
0:46:36 > 0:46:40But what could be worth such a mammoth journey?
0:46:42 > 0:46:47The long hours of summer daylight mean the seas are full of life.
0:46:47 > 0:46:50As much fish as you could possibly want.
0:46:50 > 0:46:54And the terns flock here in their thousands.
0:47:08 > 0:47:11He brings a little gift for his lifelong partner.
0:47:13 > 0:47:15By the time they get back to Antarctica
0:47:15 > 0:47:18it will be summer again there.
0:47:18 > 0:47:20Their lives are lived in an endless summer.
0:47:22 > 0:47:25No other animal spends longer in the sunshine.
0:47:30 > 0:47:33And they've come back here to raise their chicks.
0:47:34 > 0:47:37It seems like an adventurous thing to do,
0:47:37 > 0:47:39bringing up your family on the road.
0:47:42 > 0:47:44But the summer feeding is so good here,
0:47:44 > 0:47:47in three weeks these chicks will have grown
0:47:47 > 0:47:49more than five times heavier.
0:47:53 > 0:47:55And they don't waste a morsel.
0:48:02 > 0:48:07This chick was up and running less than three days after it hatched.
0:48:07 > 0:48:11But in about a month it's going to have to fly the massive return trip
0:48:11 > 0:48:13to the other end of the world.
0:48:14 > 0:48:20Over its lifetime it could clock up a total of 1.5 million miles.
0:48:22 > 0:48:23It's certainly ambitious.
0:48:36 > 0:48:39These epic summer trips are worth it
0:48:39 > 0:48:42when you're trying to give your family the best start in life.
0:48:53 > 0:48:57And sometimes it takes a monumental effort.
0:49:01 > 0:49:03In the warm waters off northern Australia,
0:49:03 > 0:49:06a green turtle is about to come ashore.
0:49:13 > 0:49:16She's coming back to the very beach where she was born.
0:49:25 > 0:49:30She might have swum 1,500 miles to get here.
0:49:49 > 0:49:51And she's not alone.
0:49:54 > 0:49:55At the height of summer,
0:49:55 > 0:49:59there might be more than 20,000 females landing on this one island.
0:50:05 > 0:50:08It's the world's biggest gathering of green turtles.
0:50:14 > 0:50:17These females may be 50 years old,
0:50:17 > 0:50:18but they're still raising babies.
0:50:20 > 0:50:24They come ashore when the temperature is just right for their eggs.
0:50:29 > 0:50:30When night falls,
0:50:30 > 0:50:33it's a scramble to find a nesting place in the warm sand.
0:51:01 > 0:51:06Each expectant mother carefully digs out a hole with her back flipper.
0:51:11 > 0:51:15But with hundreds of mothers choosing this perfect moment to lay their eggs,
0:51:15 > 0:51:16there's a problem.
0:51:19 > 0:51:20In the rush to dig their nests,
0:51:20 > 0:51:23they almost bury each other in sand.
0:51:32 > 0:51:35But they haven't come all this way to give up now.
0:51:36 > 0:51:38They might lay more than 100 eggs.
0:51:48 > 0:51:51These mothers won't ever see their babies.
0:51:52 > 0:51:55At daylight they'll go back to the sea.
0:51:58 > 0:52:02They will leave it to the warmth of the sand to do the rest.
0:52:23 > 0:52:25After two months, the eggs hatch.
0:52:28 > 0:52:31And the warmth has had an extraordinary effect.
0:52:35 > 0:52:38If the sand was over 30 degrees centigrade,
0:52:38 > 0:52:41the baby turtles will hatch as females.
0:52:42 > 0:52:45Under 28 degrees, and the babies will all be male.
0:52:50 > 0:52:53These little turtles' lives have already been predestined
0:52:53 > 0:52:55by the strength of the summer sun.
0:53:01 > 0:53:05This turtle is on the start of her own epic migration.
0:53:12 > 0:53:15But one summer, after 30 years at sea,
0:53:15 > 0:53:17she'll be back to this very beach.
0:53:29 > 0:53:34But one young animal has to take an even riskier long-distance trip.
0:53:34 > 0:53:37On a warm day in midsummer
0:53:37 > 0:53:40it has to take the biggest gamble of its life.
0:53:43 > 0:53:47On the Hawaiian atoll of French Frigate Shoals,
0:53:47 > 0:53:49young black footed albatrosses are getting to grips
0:53:49 > 0:53:52with their two-metre wingspan.
0:53:53 > 0:53:56They've spent the last five months preparing for this one moment.
0:53:56 > 0:54:01Their parents have already left and there's nothing to eat.
0:54:01 > 0:54:02They're on their own
0:54:02 > 0:54:06and ahead of them is a 1,500 mile journey north
0:54:06 > 0:54:08to better summer fishing grounds.
0:54:13 > 0:54:16First, they have to get airborne.
0:54:18 > 0:54:20But even that takes some practice.
0:54:30 > 0:54:32There's not much of a run-up.
0:54:32 > 0:54:35Their very first flight will need a take off over water.
0:54:41 > 0:54:45And in the shallows there's something waiting for them to fail.
0:54:52 > 0:54:53Tiger sharks.
0:54:56 > 0:55:00They know full well these young albatrosses will be around here in summer
0:55:00 > 0:55:02and learning to fly.
0:55:02 > 0:55:06They gather on the very day the chicks take their clumsy maiden flight.
0:55:09 > 0:55:10And they wait.
0:55:12 > 0:55:15Every young bird has to leave the island.
0:55:15 > 0:55:17There's no alternative.
0:55:17 > 0:55:19It's do or die.
0:55:24 > 0:55:26A lucky escape for one.
0:55:33 > 0:55:35Another prepares to launch.
0:55:42 > 0:55:44There's no going back now.
0:55:55 > 0:55:57It's vital not to land in the water.
0:56:15 > 0:56:17From here, take off is even harder.
0:56:20 > 0:56:23This young albatross has to make an almighty effort.
0:56:28 > 0:56:30She's done it.
0:56:33 > 0:56:36If she's lucky, she'll spend the next 40 years roaming the ocean.
0:56:38 > 0:56:42But on this one day in this one summer
0:56:42 > 0:56:43she's made the right start.
0:56:49 > 0:56:51Summer moves on,
0:56:51 > 0:56:54and life is getting ready for the next seasonal challenge.
0:56:56 > 0:57:00As autumn kicks in in the mountains of North America,
0:57:00 > 0:57:02pikas will finish their collecting.
0:57:06 > 0:57:07In the forests,
0:57:07 > 0:57:09black bears will be getting ready
0:57:09 > 0:57:13to spend the next five months fast asleep.
0:57:19 > 0:57:22And the king penguin chicks will feel their world cool down
0:57:22 > 0:57:24as their long winter approaches.
0:57:27 > 0:57:30Summer is all about seizing the moment
0:57:30 > 0:57:34and enjoying nature's most lavish bounty.
0:57:34 > 0:57:36Life is busy.
0:57:39 > 0:57:41And it might have its challenges.
0:57:44 > 0:57:46But there are pleasures, too.
0:57:49 > 0:57:52Autumn is just around the corner
0:57:52 > 0:57:56so you need to make the most of the good times while they're here.