0:00:05 > 0:00:07Our planet is a place of constant change.
0:00:09 > 0:00:12Each year, the seasons shift and life is transformed.
0:00:15 > 0:00:18But there are places where the changes are so epic in scale,
0:00:18 > 0:00:21they can be seen from space.
0:00:23 > 0:00:27In this series, we reveal three of the most miraculous transformations.
0:00:30 > 0:00:32The islands of Svalbard.
0:00:32 > 0:00:36Within a few weeks, frozen wastelands burst into life.
0:00:38 > 0:00:41The African Okavango.
0:00:41 > 0:00:44A desert transforms into a magical water world.
0:00:47 > 0:00:49And the mysterious forests of New England
0:00:49 > 0:00:52erupting in a blaze of seasonal colour.
0:00:56 > 0:01:00Life finds the most ingenious and surprising ways to thrive...
0:01:02 > 0:01:05..in the world's most fast-changing landscapes.
0:01:25 > 0:01:27The Kalahari basin.
0:01:30 > 0:01:352.5 million square kilometres of flat sand and scrub.
0:01:37 > 0:01:40This desert stretches across southern Africa.
0:01:42 > 0:01:45But at its heart lies a river.
0:01:45 > 0:01:47A river that never reaches the sea.
0:01:47 > 0:01:51And once a year, it floods.
0:01:54 > 0:02:00Over five months, waters spread across a vast area of the Kalahari,
0:02:00 > 0:02:03transforming it into a wonderland.
0:02:09 > 0:02:12The Okavango Delta.
0:02:22 > 0:02:25This is the story of how nature creates a unique,
0:02:25 > 0:02:30flourishing wetland out of one of earth's great deserts.
0:03:01 > 0:03:04Our story begins in the heart of the Delta.
0:03:07 > 0:03:09The dry season is well advanced
0:03:09 > 0:03:12and water is becoming scarcer by the day.
0:03:15 > 0:03:18At this time of year, predators rule.
0:03:33 > 0:03:36Animals have another six months to wait
0:03:36 > 0:03:41before the flood turns this land back into a lush wetland.
0:03:48 > 0:03:51Sable antelope.
0:03:51 > 0:03:55After grazing on dry grass, they have to drink at a stagnant pool.
0:03:59 > 0:04:01But they're nervous.
0:04:04 > 0:04:07Predators watch their every move.
0:04:18 > 0:04:21For a leopard, though, a sable's size
0:04:21 > 0:04:25and lethal scimitar horns pose too much of a risk.
0:04:28 > 0:04:31There are plenty of easier targets.
0:04:42 > 0:04:44A family of warthogs.
0:04:44 > 0:04:46GRUNTING
0:04:46 > 0:04:49Where once there was a wide river,
0:04:49 > 0:04:52they use their tough snouts to truffle for bulbs.
0:04:56 > 0:04:59But it's hard work in this dry, sun-baked ground.
0:05:02 > 0:05:06And having your snout in the sand is decidedly risky.
0:05:25 > 0:05:26GRUNTING
0:05:29 > 0:05:30SQUEAL!
0:05:30 > 0:05:33FRANTIC SQUEALING
0:05:40 > 0:05:42SQUEALING
0:05:49 > 0:05:52The leopard drags its kill to a hiding place,
0:05:52 > 0:05:54where it can dine in peace.
0:06:01 > 0:06:03The warthog will keep it going for a week.
0:06:07 > 0:06:10The dry season means good hunting for top predators.
0:06:13 > 0:06:16For everyone else, food is scarce.
0:06:19 > 0:06:22Chacma baboons survive through their knowledge...
0:06:25 > 0:06:26..and eclectic taste.
0:06:26 > 0:06:28BUZZING
0:06:28 > 0:06:32Elephant dung is a valuable source of seeds and insects.
0:06:32 > 0:06:35CHATTERING
0:06:47 > 0:06:50But it looks like there's an appealing alternative.
0:06:50 > 0:06:53A tree that fruits even in the dry season.
0:06:53 > 0:06:55A fan palm.
0:07:08 > 0:07:12The fruit is nutritious, if a bit tough and pithy.
0:07:18 > 0:07:20But what's this?
0:07:23 > 0:07:27Elephants will eat virtually any vegetation.
0:07:27 > 0:07:29And fruit is their favourite.
0:07:29 > 0:07:31They can smell it from several kilometres away.
0:07:46 > 0:07:49For the baboons, the feast is over.
0:07:49 > 0:07:51TRUMPETING
0:07:56 > 0:07:59The fruit may be 20 metres up and out of reach,
0:07:59 > 0:08:01but the elephant's strategy is simple.
0:08:02 > 0:08:05Brute force.
0:09:05 > 0:09:10For a crafty baboon, though, it sometimes pays to hang around.
0:09:15 > 0:09:17It's spotted one that the elephants missed.
0:09:29 > 0:09:33Nearby, at a shrinking pool, something agitates the water.
0:09:40 > 0:09:41Mouths gulp at the surface.
0:09:44 > 0:09:48It's crowded with giant catfish up to a metre-and-a-half long.
0:09:51 > 0:09:55There's no oxygen left in the water for their gills to use.
0:09:55 > 0:09:59But these fish also have lung-like organs that breathe air.
0:10:05 > 0:10:10Every day, under the Kalahari sun, more water evaporates.
0:10:13 > 0:10:17African fish eagles gather expectantly for a banquet.
0:10:36 > 0:10:40In desperation, some catfish attempt to make a run for it,
0:10:40 > 0:10:42using their fins to propel them.
0:10:45 > 0:10:49Now exposed, they are easy targets for eagles and jackals.
0:10:52 > 0:10:54SQUAWKING
0:11:17 > 0:11:19These catfish have run out of time.
0:11:23 > 0:11:26Within two weeks, the pool has vanished.
0:11:44 > 0:11:48When it floods, there will be plenty of water for everyone.
0:11:48 > 0:11:52But now, at the end of the dry season,
0:11:52 > 0:11:55elephants must keep walking in search of water.
0:11:58 > 0:12:00LOW ROAR
0:12:05 > 0:12:08Her calf needs 15 litres of milk a day,
0:12:08 > 0:12:12so she must find over 100 litres of water for both of them.
0:12:15 > 0:12:19But elephants have a special technique to get at fresh water.
0:12:22 > 0:12:24No other animal has such power.
0:12:30 > 0:12:34Using their tusks, they pile-drive into the flood plain
0:12:34 > 0:12:36until they reach water beneath the surface.
0:12:36 > 0:12:39TRUMPETING
0:12:54 > 0:12:58In doing so, elephants create a lifeline for others.
0:13:00 > 0:13:02A hyena and jackal wait their turn.
0:13:05 > 0:13:08Elephants with calves are not to be messed with.
0:13:10 > 0:13:11So they dive in when they can.
0:13:18 > 0:13:22But this jackal may have pushed its luck a little too far.
0:13:28 > 0:13:30CHATTERING
0:13:42 > 0:13:44BIRDSONG
0:13:50 > 0:13:54For insect-eating birds, food is increasingly hard to find.
0:14:00 > 0:14:04This mound makes a good lookout post.
0:14:04 > 0:14:06But if only it knew what's inside.
0:14:13 > 0:14:17It's a fortress for Macrotermes termites.
0:14:18 > 0:14:20A colony a million strong.
0:14:22 > 0:14:27A termite's mound is just the hub of an underground city.
0:14:27 > 0:14:30Six kilometres of foraging tunnels.
0:14:32 > 0:14:35Here, the Macrotermes process dead vegetation into food.
0:14:38 > 0:14:40The mound is perfectly engineered
0:14:40 > 0:14:43to keep air at constant temperature and humidity.
0:14:43 > 0:14:46Protecting the termites from drying out.
0:14:49 > 0:14:51But these mounds will also prove essential
0:14:51 > 0:14:55for the survival of many other species when the floods come.
0:15:06 > 0:15:10By the end of October, dryness and increasing temperatures
0:15:10 > 0:15:14turn the once-lush Okavango Delta into a tinderbox.
0:15:14 > 0:15:16FLAMES ROAR
0:15:27 > 0:15:30But these birds seem to be attracted to the flames.
0:15:39 > 0:15:43For the lilac-breasted roller and the fork-tailed drongo,
0:15:43 > 0:15:45it's a great opportunity.
0:15:45 > 0:15:48Because the fire flushes out a bounty of insects.
0:16:14 > 0:16:16Up to a quarter of the Okavango flood plain
0:16:16 > 0:16:18can burn in a single year.
0:16:21 > 0:16:23For most of the plants and animals that live here,
0:16:23 > 0:16:27the end of the dry season can't come soon enough.
0:16:42 > 0:16:43THUNDERCLAP
0:16:43 > 0:16:45RAIN PELTS
0:16:45 > 0:16:49November brings a little respite to the parched land.
0:16:49 > 0:16:51THUNDERCLAP
0:16:51 > 0:16:54Warm, humid air moves in from the tropics.
0:16:57 > 0:16:59Rain in the Kalahari.
0:17:06 > 0:17:09Just enough to green the delta.
0:17:20 > 0:17:21BIRDSONG
0:17:28 > 0:17:30CHATTERING
0:17:34 > 0:17:36The baboon troop has grown in number.
0:17:42 > 0:17:43SQUEALING
0:17:59 > 0:18:03These youngsters were born just in time to enjoy what the rains bring.
0:18:06 > 0:18:08More trees have come into fruit.
0:18:08 > 0:18:11It makes for a delicious breakfast.
0:18:16 > 0:18:18But there's a downside to such a wonderful scent.
0:18:18 > 0:18:20TRUMPETING
0:18:25 > 0:18:28Sure enough, elephants aren't far away.
0:18:28 > 0:18:30TRUMPETING
0:18:34 > 0:18:36GENTLE ROARING
0:18:46 > 0:18:48The troop scatters.
0:18:48 > 0:18:50SQUEALING
0:19:01 > 0:19:03Maybe it's time to move on.
0:19:07 > 0:19:10Mothers carry their newborns safely underneath,
0:19:10 > 0:19:12where they can keep suckling.
0:19:15 > 0:19:17But the older ones must learn to ride on top.
0:19:20 > 0:19:22CHATTERING
0:19:24 > 0:19:28On these open plains, the troop must stick together.
0:19:30 > 0:19:33Some have already lost limbs to leopards.
0:19:38 > 0:19:42All these animals will soon face a new world.
0:19:49 > 0:19:53The Kalahari rains may have provided some temporary relief,
0:19:53 > 0:19:57but a much greater change is on its way.
0:19:59 > 0:20:02In distant mountains beyond the Kalahari,
0:20:02 > 0:20:07the tropical air now brings much heavier downpours.
0:20:25 > 0:20:28Rain, from highlands to the north,
0:20:28 > 0:20:31cascades ultimately into one river.
0:20:31 > 0:20:33The Okavango River.
0:20:34 > 0:20:37It creates a pulse of high water
0:20:37 > 0:20:41which takes two months to snake over a thousand kilometres
0:20:41 > 0:20:43to the top of the Okavango delta.
0:21:00 > 0:21:02It will still be another month
0:21:02 > 0:21:05before the floodwaters reach the heart of the delta.
0:21:07 > 0:21:09Here, the river always flows
0:21:09 > 0:21:13and is home to several thousand people, such as Sinabe.
0:21:14 > 0:21:17His people are descendants of both Kalahari nomads
0:21:17 > 0:21:20and fishermen from central Africa.
0:21:26 > 0:21:30As the river rises, water spills on to the surrounding land.
0:21:31 > 0:21:34Creating shallows ideal for spear-fishing.
0:21:47 > 0:21:51The rising pulse of water continues onwards.
0:21:51 > 0:21:54South, towards the dry heart of the delta.
0:21:57 > 0:22:01But to understand what happens next, we have to go back in time.
0:22:04 > 0:22:08Two million years ago, great cracks ripped through the desert floor.
0:22:13 > 0:22:17The land warped to create the shape of the Delta we know today.
0:22:22 > 0:22:26The faults define the start and finish lines for the flood
0:22:26 > 0:22:28which is to come to the main delta.
0:22:42 > 0:22:47The dry plains in the heart of the Delta will soon be transformed.
0:22:47 > 0:22:49GRUNTING
0:22:53 > 0:22:56Life here is about to be turned upside down.
0:22:59 > 0:23:01GRUNTING
0:23:08 > 0:23:10SQUEALING
0:23:10 > 0:23:13But for this family of warthogs,
0:23:13 > 0:23:16there's still a bit of time to get some truffling in.
0:23:21 > 0:23:24The last rains softened the ground.
0:23:24 > 0:23:27And now, getting at those tubers is much easier.
0:23:30 > 0:23:33For the cunning baboons, it's an unmissable opportunity.
0:23:36 > 0:23:40They muscle in to enjoy the fruits of the warthogs' hard work.
0:23:44 > 0:23:46GRUNTING
0:23:46 > 0:23:48SQUAWKING
0:23:50 > 0:23:52The baboons may have no manners,
0:23:52 > 0:23:55but the warthogs don't really seem to mind.
0:23:57 > 0:24:00Perhaps it's because the baboons provide extra security.
0:24:04 > 0:24:07But this is one food source that will soon disappear.
0:24:18 > 0:24:24Hidden in the reeds, it starts as the tiniest trickle.
0:24:24 > 0:24:28The beginning of one of Africa's greatest floods.
0:24:59 > 0:25:02As rising water spills into the main delta,
0:25:02 > 0:25:07it slows and spreads into countless, tiny rivulets.
0:25:10 > 0:25:12RHYTHMIC DRUMBEAT
0:25:29 > 0:25:31Travelling at barely a kilometre a day,
0:25:31 > 0:25:35the flood will take another four months to cover the delta.
0:25:40 > 0:25:43But straightaway, wherever water touches the land,
0:25:43 > 0:25:45it makes a remarkable impact.
0:25:52 > 0:25:54Common sand frogs spend most of the year
0:25:54 > 0:25:56buried half a metre underground.
0:26:02 > 0:26:06But now, water floods their burrows and forces them to the surface.
0:26:08 > 0:26:10They inflate to scare off any predators.
0:26:14 > 0:26:16He's off to find a female.
0:26:24 > 0:26:26For tiny creatures whose homes are in the way,
0:26:26 > 0:26:30the trickle is more like a tsunami.
0:26:32 > 0:26:35Ants are forced to evacuate their nest.
0:26:40 > 0:26:43An easy snack for blacksmith lapwings.
0:26:51 > 0:26:54Termites now face the flooding of their colony.
0:26:58 > 0:27:01They beat a hasty retreat to the safety of their mound
0:27:01 > 0:27:04as their tunnels start to flood and collapse.
0:27:08 > 0:27:12But in doing so, something miraculous happens.
0:27:12 > 0:27:14The tunnels seal themselves up.
0:27:18 > 0:27:20This blocks the flood's underground advance
0:27:20 > 0:27:23and forces the water back to the surface.
0:27:30 > 0:27:33Back inside the mound, the termites are safe.
0:27:37 > 0:27:42Incredibly, the flood provides just the opportunity they need.
0:27:45 > 0:27:47Their fragile castle, made of sand,
0:27:47 > 0:27:50requires constant maintenance and rebuilding.
0:27:51 > 0:27:54But the soil, now softened by floodwater,
0:27:54 > 0:27:58is easy to transport to damaged parts of the mound.
0:28:04 > 0:28:09Gradually, thousands of termites reconstruct their fortress.
0:28:13 > 0:28:17Repairing these mounds isn't just good for the termites.
0:28:19 > 0:28:22These structures help to create something vital
0:28:22 > 0:28:24for all the delta's wildlife.
0:28:25 > 0:28:27Its islands.
0:28:31 > 0:28:34And it all starts like this.
0:28:43 > 0:28:45Dung.
0:28:45 > 0:28:48Readymade fertiliser laden with fruits and seeds.
0:28:51 > 0:28:55Floodwater soaks up the dry side slopes of the mound
0:28:55 > 0:28:57to create the perfect bedding for new plants.
0:29:12 > 0:29:15Gradually, season-by-season,
0:29:15 > 0:29:18termite mounds become home to more and more plants.
0:29:30 > 0:29:32As they grow, they attract more animals,
0:29:32 > 0:29:37which in turn bring with them the seeds to grow even more plants.
0:29:37 > 0:29:42Sycamore fig, fan palm, marula.
0:29:42 > 0:29:45Until the termite mounds are barely recognisable
0:29:45 > 0:29:47under their lush green canopies.
0:29:57 > 0:30:01As it floods, raised areas around termite mounds become islands.
0:30:05 > 0:30:08They provide food, shelter and a refuge throughout the year
0:30:08 > 0:30:12for everything from elephants to baboons and birds.
0:30:17 > 0:30:20In the delta, once featureless desert,
0:30:20 > 0:30:25there are now around 150,000 such islands.
0:30:35 > 0:30:37For a lot of thirsty animals,
0:30:37 > 0:30:40the floods simply mean sweet drinking water.
0:30:44 > 0:30:46Elephants no longer need to dig holes.
0:30:48 > 0:30:51TRUMPETING
0:30:51 > 0:30:53CHATTERING
0:31:00 > 0:31:02GRUNTING
0:31:05 > 0:31:09Baboons, too, seem to delight in the precious liquid.
0:31:15 > 0:31:20Curious youngsters, encountering the flood for the very first time,
0:31:20 > 0:31:23don't seem to know quite what to make of it.
0:31:56 > 0:31:58The sand may look barren,
0:31:58 > 0:32:02but wherever the water touches it, something magical happens.
0:32:04 > 0:32:08Within a couple of days, billions of freshwater plankton
0:32:08 > 0:32:11begin to awake and hatch.
0:32:17 > 0:32:21Such tiny creatures are the delta's secret ingredients.
0:32:21 > 0:32:23The foundation of its food chain.
0:32:27 > 0:32:29Meanwhile, in a deeper channel,
0:32:29 > 0:32:31a mountain of foam has appeared.
0:32:34 > 0:32:37It has been created by a pair of African pike.
0:32:37 > 0:32:39Notoriously aggressive,
0:32:39 > 0:32:42but caring parents that watch over their offspring.
0:32:49 > 0:32:51Hidden safely underneath the foam,
0:32:51 > 0:32:54hundreds of fish eggs are beginning to hatch.
0:32:57 > 0:33:01The fry remain attached to the foam until they are well developed.
0:33:02 > 0:33:05And now, the delta offers plenty for them to eat.
0:33:08 > 0:33:14The tiny pike fry join small, hungry fish of 70 different species,
0:33:14 > 0:33:15swimming though the shallows
0:33:15 > 0:33:19in a nutritious soup of freshwater plankton.
0:33:33 > 0:33:36BIRDSONG
0:33:36 > 0:33:39Before long, the skies fill with birds.
0:33:42 > 0:33:45One of Africa's greatest wildlife spectacles.
0:33:48 > 0:33:51Travelling nomads from far and wide.
0:33:53 > 0:33:55The reason they're here?
0:33:55 > 0:33:59Wherever water covers the land, it fills up with little fish.
0:34:03 > 0:34:07Each of the birds has its own special technique for catching them.
0:34:10 > 0:34:13A saddle-billed stork jabs at its prey.
0:34:19 > 0:34:22African spoonbills have the perfect equipment
0:34:22 > 0:34:24for filtering out the finest morsels.
0:34:40 > 0:34:44Black egrets use their wings to form canopies over the water.
0:34:44 > 0:34:48The shade lures nervous fish desperate for cover.
0:35:01 > 0:35:03Others attack directly from above.
0:35:06 > 0:35:08A pied kingfisher.
0:35:13 > 0:35:14At 25 centimetres long,
0:35:14 > 0:35:17it's the world's largest hovering bird.
0:35:29 > 0:35:32Hovering demands a lot of energy,
0:35:32 > 0:35:36so they have to catch a quarter of their weight in fish every day.
0:35:40 > 0:35:43Keeping its head perfectly still,
0:35:43 > 0:35:47about ten metres above the water, it sees movement.
0:35:50 > 0:35:53Then drops in a controlled dive.
0:35:55 > 0:35:59If the fish sees it, the kingfisher can still abort and save energy.
0:35:59 > 0:36:02If not, it commits and dives rapidly.
0:36:05 > 0:36:07It's worth the effort.
0:36:07 > 0:36:10Hovering allows them to hunt in the middle of the plains,
0:36:10 > 0:36:12where the pickings are especially rich.
0:36:26 > 0:36:28The bird kills its prey with a blow to the head.
0:36:31 > 0:36:35But before it can swallow, it must flip the fish, head first,
0:36:35 > 0:36:38or the spines will stick in its throat.
0:37:18 > 0:37:21Within a few months, another type of organism
0:37:21 > 0:37:24vital to the delta breaks the surface.
0:37:25 > 0:37:28Dozens of species of aquatic grasses,
0:37:28 > 0:37:30sedges and water lilies.
0:37:50 > 0:37:53At dawn, day lilies open
0:37:53 > 0:37:56to attract pollinating bees and flies.
0:38:25 > 0:38:29As dusk approaches, the day lilies begin to close,
0:38:29 > 0:38:31and give way to the night shift.
0:38:36 > 0:38:39Night lilies open their brilliant petals...
0:38:40 > 0:38:44..bright enough to attract insects in the moonlight.
0:38:46 > 0:38:51Water lilies, flourishing in the middle of the Kalahari desert.
0:38:57 > 0:38:59Perhaps the greatest miracle of the delta.
0:39:04 > 0:39:07And only possible thanks to one thing.
0:39:10 > 0:39:14Nature has found a unique way to keep the water of the Delta
0:39:14 > 0:39:16pure, very low in toxic salts.
0:39:20 > 0:39:24Its secret lies with those extraordinary islands.
0:39:35 > 0:39:38Trees on the islands act as pumps,
0:39:38 > 0:39:40sucking in water from the surrounding swamp.
0:39:43 > 0:39:45As they do so,
0:39:45 > 0:39:49salts in the water are deposited in the sand of the islands.
0:39:53 > 0:39:55By extracting salt from the water,
0:39:55 > 0:39:58it's as though the islands are kidneys,
0:39:58 > 0:40:00removing waste from the bloodstream.
0:40:05 > 0:40:10This way, the islands keep the Delta's waters fresh
0:40:10 > 0:40:12and able to nurture abundant life.
0:40:36 > 0:40:40As the morning sun heats the ground, rising vapours everywhere
0:40:40 > 0:40:44reveal that water has spread right across this plain.
0:40:45 > 0:40:50It's a transformation that turns the tables between predator and prey.
0:40:54 > 0:40:58Red lechwe appear in large numbers, looking for their favourite food...
0:41:00 > 0:41:02..tender aquatic plants.
0:41:11 > 0:41:14But a hyena hopes to take advantage of their distraction.
0:41:22 > 0:41:26It just needs to get a little closer.
0:41:32 > 0:41:33Time to run for it.
0:41:44 > 0:41:45Lechwe have large splayed hooves
0:41:45 > 0:41:49that allow them to bound at speed through shallow water,
0:41:49 > 0:41:52giving them a big advantage over any predator.
0:42:09 > 0:42:11It's an adaptation that helps to protect them
0:42:11 > 0:42:13during the time of flood.
0:42:23 > 0:42:27Soon the aquatic vegetation sprouts everywhere
0:42:27 > 0:42:29and the water becomes impassable.
0:42:35 > 0:42:37But crisscrossing the flooded plains,
0:42:38 > 0:42:41highways through the reeds appear.
0:42:44 > 0:42:49And here's their creator - a hippopotamus.
0:42:51 > 0:42:57He's a grazer and thinks nothing of bulldozing a way through.
0:42:57 > 0:43:00As he does so, he excavates a channel.
0:43:18 > 0:43:21And it's not only hippos that have to find a way through.
0:43:28 > 0:43:30In the far north of the Delta,
0:43:30 > 0:43:33Sinabe rows through dense beds of reeds.
0:43:37 > 0:43:41To get through, he seeks the help of the spirit of the river.
0:44:11 > 0:44:15Deep in the reeds, he discovers a hippo channel.
0:44:15 > 0:44:20It's a highway for fish, so the perfect place to rig a net.
0:45:05 > 0:45:08Sinabe's village is on the edge of the flood plain.
0:45:11 > 0:45:14His family know that as long as the Delta provides,
0:45:14 > 0:45:16they will never go short of food.
0:45:19 > 0:45:21He smokes the bream to preserve it
0:45:21 > 0:45:24for days when the catch isn't quite as good.
0:45:27 > 0:45:31Meanwhile, his family weave baskets out of grass from the flood plains.
0:45:31 > 0:45:35Later in the year, they will be used for catching fish.
0:46:00 > 0:46:02By July, in the heart of the Delta,
0:46:02 > 0:46:05the once-dry savanna has become a lush water-world.
0:46:09 > 0:46:14But this transformation has an odd effect on the baboons.
0:46:18 > 0:46:20SQUEALING
0:46:28 > 0:46:31Each has developed its own funny walk.
0:46:33 > 0:46:37SCREECHING AND GRUNTING
0:46:42 > 0:46:46SCREECHING
0:46:55 > 0:46:59All that is, except for the baby - who just gets a soaking.
0:47:14 > 0:47:15SCREECHING
0:47:17 > 0:47:21It seems likely that baboons don't much enjoy being in the water -
0:47:21 > 0:47:23or they may be nervous of something in it.
0:47:27 > 0:47:29Crocodiles are everywhere.
0:47:33 > 0:47:37For the troop, a flooded Delta is a lawless place,
0:47:37 > 0:47:41but a threat worse even than a crocodile has appeared.
0:47:47 > 0:47:49Lone male baboons.
0:47:53 > 0:47:55The shrinking of territory on land
0:47:55 > 0:47:58forces the loners into contact with troops.
0:48:00 > 0:48:03They may fight the troop's alpha male for control.
0:48:05 > 0:48:08If the stranger wins, he may also kill the young
0:48:08 > 0:48:10and mate with the females.
0:48:12 > 0:48:16An incumbent alpha male must keep a close eye on any rival.
0:48:19 > 0:48:21HE BARKS
0:48:22 > 0:48:28To survive, it is crucial that he lay down his authority.
0:48:29 > 0:48:34BARKING AND GRUNTING
0:48:39 > 0:48:43GRUNTING
0:48:45 > 0:48:48ROARING
0:48:48 > 0:48:51SCREECHING
0:48:51 > 0:48:54ROARING AND BARKING
0:48:55 > 0:48:58SCREECHING AND ROARING
0:49:00 > 0:49:03BARKING
0:49:10 > 0:49:14GRUNTING AND SQUEALING
0:49:21 > 0:49:24SCREECHING AND SQUEALING
0:49:26 > 0:49:28GRUNTING
0:49:29 > 0:49:31Insurgents must be sent packing.
0:49:50 > 0:49:54As the Delta floods, everywhere, tension seems to be mounting.
0:49:57 > 0:49:59Not least in the hippo community,
0:49:59 > 0:50:03where their watery territories are expanding dramatically.
0:50:07 > 0:50:10Here, too, there is a young challenger.
0:50:15 > 0:50:17The territory's resident bull snorts a warning.
0:50:19 > 0:50:23HE SNORTS
0:50:26 > 0:50:29The adversaries declare their ownership of the pool
0:50:29 > 0:50:33by vigorously spreading dung with their tails.
0:50:37 > 0:50:42SNORTING
0:50:42 > 0:50:45They yawn to display their weaponry -
0:50:45 > 0:50:47huge ivory tusks.
0:50:51 > 0:50:54SNORTING
0:50:58 > 0:51:00First, a test of strength.
0:51:04 > 0:51:07SNORTING
0:51:07 > 0:51:09The old bull makes a temporary retreat.
0:51:12 > 0:51:15Females have a vested interest in the outcome.
0:51:17 > 0:51:19They will only be prepared to accept a mate
0:51:19 > 0:51:21that can hold his own in a fight.
0:51:30 > 0:51:33The resident bull retaliates brutally.
0:51:35 > 0:51:39SNORTING
0:51:44 > 0:51:47SNORTING
0:51:47 > 0:51:51Hippos will often fight for hours and sometimes to the death.
0:52:09 > 0:52:13Finally, a brutal headlock - the coup de grace that settles
0:52:13 > 0:52:15it for the older male -
0:52:15 > 0:52:18expelling the pretender from his territory.
0:52:29 > 0:52:32Which means the resident bull passes the test
0:52:32 > 0:52:35to sire this year's crop of baby hippos.
0:52:35 > 0:52:42GRUNTING
0:52:49 > 0:52:52The young male has been injured during the retreat,
0:52:52 > 0:52:55his flank exposed to his furious pursuer.
0:52:59 > 0:53:04At least nature has arranged for him to be nursed - by these oxpeckers.
0:53:04 > 0:53:07They eat anything that might cause an infection.
0:53:09 > 0:53:11The pain is probably worth it
0:53:11 > 0:53:14and he should survive to fight another day.
0:53:25 > 0:53:27By August, the floodwaters finally reach
0:53:27 > 0:53:31the Delta's southern fault line, its maximum extent.
0:53:39 > 0:53:44The Okavango is now one of the largest inland deltas in the world.
0:53:46 > 0:53:51The whole Delta is linked by water - shallow flood plains, pools,
0:53:51 > 0:53:54and deeper channels all fed by the Okavango River.
0:54:08 > 0:54:12Billions of fish that fill the plains have grown rapidly.
0:54:21 > 0:54:26And Sinabe's wives and daughters are ready for them with their baskets.
0:54:26 > 0:54:32SINGING IN AFRICAN LANGUAGE
0:54:41 > 0:54:48SINGING CONTINUES
0:54:53 > 0:54:56SINGING STOPS
0:54:56 > 0:54:59Bulldog fish will make a fine stew.
0:55:04 > 0:55:08In the main river, something strange is happening.
0:55:08 > 0:55:11The waters appear to be boiling.
0:55:18 > 0:55:21It's catfish, taking gulps of air at the surface.
0:55:26 > 0:55:28And they are here in their millions.
0:55:32 > 0:55:35Before the flood recedes, they return from their hunting grounds
0:55:35 > 0:55:40in the far reaches of the Delta to the safety of the deep channels.
0:55:44 > 0:55:47Amongst the papyrus, they hunt smaller fish.
0:56:06 > 0:56:09Flocks of egrets arrive to join in the feast.
0:56:31 > 0:56:32No-one is safe in the mayhem.
0:56:42 > 0:56:46African fish eagles swarm and dive-bomb the catfish.
0:56:50 > 0:56:54Millions of fish that grew fat out in the flood plains
0:56:54 > 0:56:57bring life back to the river that brought them water.
0:57:14 > 0:57:16When it's needed most,
0:57:16 > 0:57:21the flood creates a vast oasis in the desert - a wonderland.
0:57:21 > 0:57:25Its 10,000 square kilometres of crystal waters
0:57:25 > 0:57:30attracting animals from all over the dry Kalahari desert.
0:57:41 > 0:57:44HE ROARS
0:57:47 > 0:57:50HE ROARS
0:57:57 > 0:58:00But these waters will never reach the sea.
0:58:00 > 0:58:06They will soon begin to evaporate or simply sink into the Kalahari sand,
0:58:06 > 0:58:11as the Okavango Delta gradually returns to dry savanna.