Africas Desert River
Transcript
00:00♪♪
00:27Where a great African river meets the parched heart of the Kalahari
00:32lies a land of profound beauty,
00:35the Okavango Delta.
00:39Each year, the Okavango's waters flow across thousands of square miles of sand,
00:45giving birth to a flooded desert.
00:50Within its breathtaking vistas, lurk hidden dangers
00:53and rare and extraordinary creatures.
01:01The Delta's skies ring with the cry of eagles,
01:05and its waters teem with life.
01:12There is no other system quite like it on Earth,
01:15and few so complex.
01:21On the northern edge of Botswana's Kalahari Desert,
01:24a river comes to a remarkable end far from the sea.
01:28Its waters spread across a vast flat plain,
01:32the desert interior of southern Africa.
01:36But for its first 60 miles, the river is confined between two
01:41parallel fault lines in a region known as the Panhandle,
01:45where it meanders like a giant snake.
02:03Besides an endless supply of water, the Okavango brings with it large amounts of
02:07silt, sand, and dissolved nutrients. Together,
02:10they produce a five million acre paradise in the middle of a dry world.
02:28Laid three months ago, crocodile eggs hatch
02:31when the waters start to rise.
02:40Within weeks, the youngsters will disperse in every direction.
02:44Most will succumb to predators, some may remain in the Panhandle,
02:48and a few could end up hundreds of miles away, stranded in the desert.
02:53Their fortunes will follow the water in both its rise
02:57and fall.
03:01The Panhandle's lush papyrus beds support a rich supply
03:05of insects and fish, a perfect nursery for small crocodiles.
03:10Up to 10 feet thick in places, these great floating mats
03:13stretch as far as the eye can see, dwarfing
03:17even elephants.
03:30As they forage, the elephants tear loose pieces of papyrus,
03:34launching a stowaway into the river.
03:39Heading into open water, this tiny crocodile drifts into danger.
04:09Crocodiles rely on camouflage, instinct, and experience for survival.
04:19Living long enough to acquire the experience is the challenge.
04:24The fish eagle can spot prey from thousands of feet in the air,
04:43but young crocodiles have excellent vision too.
04:55Still, out of the many thousands of crocodiles hatched in a season,
05:00only a few will grow to maturity.
05:05As the waters peak, large sections of papyrus can break away
05:09and float downstream.
05:15These circular islands often wash into small channels.
05:19Blocked off, the channels may eventually vanish,
05:22but elephants and hippos are always clearing old channels
05:26and forging fresh ones.
05:29Where does all this water come from?
05:35For several months each year, rains in distant mountains,
05:38augmented by local rains, send a surge of water
05:42through the panhandle. It will take nearly half a year
05:46to spill out into the desert at the other end.
05:51The water is spread underneath the papyrus mats,
05:53lifting the entire surface like a huge raft.
06:03Though it looks solid, the papyrus is not firmly anchored to the ground.
06:11Beneath its protective roof, crocodiles and a wealth of other small creatures
06:16find shelter.
06:28The panhandle acts as a giant filter for the oak of Angkor.
06:32Countless tiny papyrus roots comb the waters,
06:35extracting nutrients.
06:41After flowing through many miles of roots, the waters emerge,
06:45crystal clear.
07:02At the edge of the papyrus lurks a hunter,
07:05armed with razor-sharp interlocking teeth.
07:10The tigerfish can strike with lightning speed both
07:13below the surface and above it.
07:17The lily trotter is hunting too, unaware that it is also being stalked.
07:32But most predators here are also prey.
08:09The wind brings a changing of the guard.
08:12Eagles roost just as the fishing owls sound their booming calls.
08:34From below the papyrus, small fish and insects come out
08:37under cover of darkness. They are the staple diet of little crocodiles.
08:47In this watery world, the Pell's fishing owl is the eagle of the night.
08:53With broad and powerful five-foot wings and talons like grappling hooks,
08:57it lifts heavy prey straight out of the water.
09:00Its main target is fish, but a small crocodile
09:04will do.
09:07This juvenile owl still has a lot to learn.
09:14With its large, sensitive eyes, it must judge the refraction of the water's
09:19surface and catch a moving fish in the dark.
09:27The Pell's fish are not afraid of water.
09:32Diving into the water, it risks crocodile attack,
09:36but the owl's special lair of downy feathers
09:39prevents it from sinking, so it can make a quick escape.
09:44The forlorn cry of the young owl signals his increasing hunger.
09:49His parents are mating and no longer feed him.
09:53Suddenly, he's on his own.
10:24A worthy opponent rises up to meet the waters.
10:28Fire sweeps across the panhandle as if an epic battle is being waged between
10:33the water and the flames. Together,
10:37they will reshape this land of extremes.
10:42Oils in the lush green papyrus flare up, igniting the straw-like stalks.
10:58In the face of fire, escape is the only option.
11:12Even creatures like the puff adder that normally shy away from water
11:16must plunge in or perish.
11:26Out of this elemental struggle, the Okavango is reborn.
11:42In dry periods, fires often burn all the way through the papyrus
11:46to the lair of peat lying on the delta's floor.
11:52There, it can smolder for months or even years
11:56until it finally reaches the sand.
12:00In this way, old, choked channels may be reopened
12:04as advancing waters find new paths and directions.
12:12The waters, too, sculpt the delta,
12:16redistributing sand and cutting through existing islands.
12:28They carve out steep banks where rainbow-colored birds
12:32find safe nesting sites.
12:37This haven for white-fronted bee-eaters will not last forever.
12:45Next season, it may well crumble and wash away completely.
12:51But for a while, the bee-eaters grace their sandy bank
12:55with dazzling colors.
13:07Outside the bank's holes, danger is never far away.
13:21Change is stirring throughout the panhandle
13:25as the surge of water passes and water levels lower.
13:29While most fish breed in the dense underwater plants
13:33during high water, certain kinds of cichlid lay their eggs
13:37in open, shallow water.
13:43Their nests pockmark the sandy bottom.
13:47Adults excavate bowl-shaped depressions
13:51for brooding their young.
13:56Since large predatory fish live primarily in deep water,
14:00the cichlid nurseries are out of their reach.
14:04Nor can they hunt below the papyrus any longer.
14:08For now, the rafts have lowered and come to rest
14:12on the delta's floor.
14:16Thousands of small fish are forced into the open channels,
14:20exposing them to attack.
14:26The sudden availability of fish
14:30coincides with the mating season of the fish eagle.
14:34The sudden availability of fish
14:38coincides with the mating season of the fish eagle.
14:43The sudden availability of fish
14:47coincides with the mating season of the fish eagle.
15:03Without their papyrus shield,
15:07small fish cling to the roots on the river's edge.
15:11Tiger fish, too, patrol the fringes of the channel.
15:29Above them all, the fish eagle hunts the hunters.
15:34Above them all, the fish eagle hunts the hunters.
15:38When the fish are scarce, eagles need large territories.
15:42But the profusion of fish in this channel
15:46has brought many pairs to a close.
15:50When the fish are scarce, eagles need large territories.
15:54But the profusion of fish in this channel
15:58has brought many pairs to a close.
16:02The fish eagle hunts the hunters.
16:07But the profusion of fish in this channel
16:11has brought many pairs to a close.
16:16The fish eagle hunts the hunters.
16:36Their battle is a dizzying display.
16:40By locking talons, fish eagles avoid seriously injuring each other.
16:44Living in the water presents a very real danger from crocodiles.
17:14Besieged from above, it's trapped there.
17:44They're trapped.
18:04Calm returns to the channel once more.
18:08As it relaxes, the eagle fluffs its feathers,
18:13the water enhanced by the setting sun.
18:33Lily-covered backwaters provide good cover for the young crocodiles.
18:43But fish eagles zero in on even the slightest movement.
18:47You can see that the profusion of fish
18:51has brought many pairs to a close.
19:05But fish eagles zero in on even the slightest movement.
19:17A
19:36lucky escape and a valuable learning experience.
19:48Fishing owls hide in the dark wooded islands along the channels during the day.
19:56Owls and eagles are about the same size but they are not equals.
20:02Despite the easy mark, the owl will not hunt for any movement could set the eagle upon
20:08it.
20:09A fight the owl would lose.
20:23For the next few months the filtered waters from the panhandle fan out into the heart
20:27of the delta.
20:29This permanent wetland is always lush and green.
20:39Piercing sunlight and a slowing current foster a multitude of aquatic plants.
20:55Though still containing some dissolved minerals, these waters, once opaque, are now as clear
21:01as glass.
21:10The tranquil heart of the wetlands belongs to the plants.
21:18But it is below the greenery that another key to this astonishing system is discovered.
21:23The plants sit above a dense layer of peat.
21:27Up to six feet thick in places, it holds water like an immense sponge and retards its flow.
21:49Only very large animals can successfully navigate the wetlands.
21:55With little game available, just a few crocodiles live here, though they can grow to enormous
22:00size.
22:03They stalk the hippopause, which slice through the vegetation, revealing the peat and sand
22:09beneath.
22:36Antelopes and hippos move easily through the maze of channels and dense plants as they
22:41search for food.
22:57Only one antelope resides in the deeper waters of the wetland, the graceful and elusive sitatunga.
23:05Its elongated hooves keep it from sinking as it travels over marsh.
23:18It's a prime target for big crocodiles.
23:37Many young crocodiles have made it into the wetland.
23:51Now double in size, they are no longer quite as vulnerable, at least to attacks by a saddle-billed
24:27On the fringes of the permanent wetland lives another water antelope.
24:50In huge herds, the red fletchway keeps to the shallows, where they are safe from most
24:55predators.
24:57When the seasonal surge of water advances beyond the wetland, they will follow it to
25:01new grazing.
25:03But even as the Okavango rises, water is being lost.
25:11Exposed to the intense African sun and dry desert air, water evaporates so fast that
25:17this area should be a vast salt marsh.
25:20But here, trees suck up water faster than it evaporates, causing salts to concentrate
25:26under islands.
25:27The water is left fresh and pure, but the white salt islands are completely barren.
25:41The white islands are isolated enough that bee-eaters will forego the safety of their
25:46vertical river banks and dig their nests on flat ground.
26:14As the dry season takes hold in the Kalahari, elephants invade the wetland, seeking one
26:31of their favorite foods, the ripe fruit of the ivory palm.
26:35But getting it requires timing and precision.
26:40Planting the tree is a skill, and some elephants are more talented than others.
27:08Over the past six months, the surge of water has filtered through the panhandle and been
27:13held back by the permanent wetland.
27:15Now it seeps out into the dry floodplain.
27:19A thin sheet of clean, clear water spills onto the grasslands and surrounds the wooded
27:27islands.
27:34Coming at the driest time of year, long after the last meager desert rains, the water's
27:40arrival seems like magic.
27:49Lions are symbols of big-game country.
27:53Within their territories, the lions now track the new water's flow, anticipating the coming
27:58of the great herds, for they know that where water flows, buffalo are soon to follow.
28:15Older lions have seen this all before, but to a young cub, the transformation is astonishing
28:22and slightly suspicious.
28:32Along with the waters come a host of new visitors to the grassland.
28:37A climbing perch can breathe air to escape the water and crawl to safety using special
28:42gill covers, a distinct advantage in a land that is alternately wet and dry.
28:53The swelling waters flush insects, mice, and other small prey out of their grassy hiding
28:58places and into the open.
29:21These shallows, rich in prey, make good hunting for a young crocodile.
29:51The
30:15unusual binocular vision of the climbing perch gives it pinpoint accuracy when leaping
30:20for insects.
30:50As the waters advance, the buffalo herds hasten across the parched plains to meet the
30:59filling pools.
31:02For months they have been confined to the sparse grazing on the edges of the permanent
31:06wetland.
31:07Finally, they can wander the entire floodplain, cropping the fresh green shoots that spring
31:13up along the water's path.
31:33The lions of the Okavango do not shy away from water, especially if prey is on the other
31:38side.
31:52Faithful but alert, they watch the buffalo closely for signs of weakness.
33:22Wherever water goes, so go the crocodiles.
33:52Wild dogs hunt here too, treading the water cautiously.
33:56They track the same prey, but often fall to crocodiles themselves.
34:19After several weeks, the waters inundate thousands of square miles of floodplain.
34:25To travel anywhere, the animals must cross water.
34:30Higher grounds become islands in the shallows.
34:39Some thickets provide good hiding places for prey and predator alike.
34:48Later, this lioness may conceal her cubs in it, but at the moment she's caught the scent
34:56of something interesting – a warthog.
35:27As if to mark an end to paradise, the dry season has brought fire to this land of water.
35:34Flames lay waste the floodplain.
35:38But brittle grass goes up like tender.
35:58For now, the island of the lions remains unscathed.
36:28The lioness and her cubs seem unaware of the peril encircling them.
36:42A strong wind and a live spark are all that stand between them and disaster.
37:02While most animals simply flee, the weak are easily trapped.
37:30Fire can work to a lion's advantage.
37:38The lioness leaves for the hunt.
37:42The cubs know to stay near the thicket till her return.
38:12On an island untouched by fire, a sausage tree has attracted several animals.
38:43These sausages, a prized fruit, are as tough as gourds.
38:58Baboons have their own way of tearing them apart.
39:01It takes two hands, one foot, and strong teeth.
39:27With the water rapidly disappearing, there are few pools left deep enough for hippos.
39:37Nearby, lechwe rest, never straying far from water, their only safe haven.
39:44Soon they must retreat to the permanent wetland.
40:06Soon, hot, these waters.
40:36The age-old rival of the wild dogs is all too ready to profit from their efforts.
41:06In
41:35warmer temperatures, many birds nest, and snakes come out of hiding.
41:43Night jars lay their eggs directly on the ground, putting them well within reach of
41:48the aptly named egg-eater.
42:15It crushes the egg with its vertebrae to release the contents.
42:37Who would believe that so recently, this was an Eden?
42:47The herds take refuge in water, but it too is vanishing.
42:56In the end, the waters are conquered by the dry season and the desert.
43:01In the searing heat, an inch evaporates every day.
43:05The rest sinks into the sand.
43:09Soon, all is lost, save for a few large pools.
43:14But in the water's wake, succulent grass springs up, drawing enormous herds to feed.
43:29The changing conditions in the floodplain open opportunities for some, just as they
43:34close them for others.
43:45Vanishing pools are a catastrophe for fish, but a blessing to birds.
43:50From far and wide they come to harvest the annual bounty of stranded fish.
43:55Even fish eagles leave their territories to take part.
44:05The crocodiles remaining in the floodplain are forced into the shrinking pools.
44:17Those that were once prey now turn predator.
44:41The oppressive heat doesn't seem to dampen the spirits of the wild dogs.
44:45They simply head for a mud bath.
44:59Here's a curiosity unfamiliar to the dogs.
45:02Terrapins usually stay out of sight, deep in their pools.
45:10With its home drying up, it must seek a safe place to wait for the water's return.
45:17But a safe place may soon be beyond its reach.
45:47Displaced from its pool, a crocodile desperately looks for shelter.
46:12In huge swaths of the delta, fire replaces water as the dominant force.
46:42A lioness tries in vain to reach her cubs, but their hiding place has gone up in flames.
47:06Every year, thousands of animals are destroyed by the infernos that consume the delta.
47:12Most are the young, the small, or the slow moving.
47:33Sorrow for some is fortune for others.
47:37But when cover is scarce for the mouse, food is plentiful for the yellow-billed kite.
48:05The lioness calls for her cubs, while the jackal sounds an alarm.
48:36Most large animals escape unharmed.
48:39They simply walk away faster than the flames.
48:42Or they shelter in areas that have already burned.
49:01Then, out of the cinders, a small symbol of hope emerges.
49:31Now, the hard times settle in for the creatures of the plains.
50:00Wandering across miles of singed earth, the herds seek out waterholes scattered through the grasslands.
50:11And as always, the crocodiles are waiting in the last haven for the survivors of the heat and flames.
50:27But even as these pools recede, the next surge of water is on its way.
50:33Months from now, new waters will arrive to transform this changed wasteland.
50:41For here, where the Okavango's waters meet the Kalahari Desert, the delta is constantly recreated.
50:48Fire and water ravage and renew, advance and retreat.
51:00But the waters are never defeated.
51:04Far away, rains are falling in the highlands.
51:07And in time, they will spill out into the Kalahari and flood the desert once more.
52:04Thanks for watching!