- 10 minutes ago
Profiling the one great reptile that has survived since the age of the dinosaur. By exploring their world, above and below water, the secrets of their longevity become clearer.
深入剖析自恐龙时代以来唯一幸存至今的伟大爬行动物。通过探索它们的世界, 深入探究非洲、澳大利亚和佛罗里达地区的鳄鱼及其近亲——短吻鳄……
深入剖析自恐龙时代以来唯一幸存至今的伟大爬行动物。通过探索它们的世界, 深入探究非洲、澳大利亚和佛罗里达地区的鳄鱼及其近亲——短吻鳄……
Category
🐳
AnimalsTranscript
00:28The
00:30I don't know.
01:03Crocodiles hail from the great age of reptiles well over 70 million years ago.
01:10Since then the world has changed dramatically around them, but amazingly they have changed little.
01:21They're the only great reptile predator to have outlived the dinosaurs.
01:32Ancient they may be, but 70 million years on they're still the most successful freshwater predator.
01:38Most of the waterways in the tropics these days have their own species of crocodile.
01:43How come that they've been so successful for so long?
01:46Well, it seems that their design when it first appeared was already very advanced, and it's kept them successful ever
01:54since.
01:55This film reveals the nature of that success.
02:09Crocodiles may have scored an early evolutionary bullseye, but there's much more to their staying power than brute strength.
02:33Only now, by exploring their complete world, above and below water, by day and night, can we fully appreciate just
02:42how sophisticated they are.
03:09Underwater crocodiles have perfect poise.
03:12They can control their buoyancy like a submarine.
03:18To dive, they just breathe out, which reduces their lung volume.
03:23They can sink without trace.
03:36While submerged, a protective membrane closes over their eyes, like swimming goggles.
03:46Crocodiles are cold-blooded.
03:49Crocodiles are cold-blooded.
03:49They rely on the temperature of the sun and water to heat themselves up or to cool down.
04:04But when fully charged, they're capable of breathtaking power and speed.
04:16They're the most dangerous freshwater predator on the planet.
04:29Even Tyrannosaurus rex couldn't match this winning formula.
04:35It's a design that has allowed them to spread around the tropical world.
04:40This extended family includes alligators of temperate waterways.
04:46The gharials of the Indian subcontinent.
04:51And caiman of tropical South America.
05:00They even invaded the sea.
05:08Crocodiles have special glands which enable them to tolerate salt water.
05:12This is how they've colonized new rivers along the coast.
05:27But only a few species can migrate across oceans.
05:31The real specialists, the saltwater crocodiles, are affectionately known as salties.
05:36They've been seen 1,000 kilometers from land encrusted with barnacles as they search for new island homes.
05:47This pioneering spirit and their unique character has made them a universal threat.
06:15Crocodiles deserve their tough reputation, but they aren't just solitary killers.
06:21In the calm of the Florida swamps, we can begin to see them in a new light.
06:35They are reptiles with social skills.
06:39And American alligators are particularly chatty.
06:42During the breeding season, an expressive chorus of bellows, grunts and hisses rises from their densely vegetated swamps.
06:58The males are calling to distant females, but their bellows sometimes attract rivals.
07:13There are snappy ways to make your feelings known if you end up in the wrong company.
07:23The resident male only shows a bit of muscle if the rival fails to get the message.
07:46He's made his point, and he can now focus on finding a mate.
07:58He's made his point, and he can now focus on finding a mate.
07:59Vibrations within his muscle walls send sound waves rippling out into the swamp.
08:04Powerful enough to make the water dance.
08:08Powerful enough to make the water dance.
08:17Powerful enough to make the water dance.
08:22Powerful enough to make the water dance.
08:24Powerful enough to make the water dance.
08:26Powerful enough to make the water dance.
08:27Powerful enough to make the water dance.
08:28Powerful enough to make the water dance.
08:28Powerful enough to make the water dance.
08:29Powerful enough to make the water dance.
08:30Powerful enough to make the water dance.
08:32Powerful enough to make the water dance.
08:34Powerful enough to make the water dance.
08:34Powerful enough to make the water dance.
08:34Powerful enough to make the water dance.
08:36Powerful enough to make the water dance.
08:37that human ears can't hear it.
08:39But these subsonic calls have astounding penetration,
08:44travelling four times faster and further under the water.
08:50Only with special low-frequency recordings
08:53can we appreciate what the female alligator hears.
09:07She finds his romantic rumblings irresistible.
09:54Even though the call may come from the remotest parts of the swamp,
09:58she is soon on his wavelength.
10:00Then they have a more intimate conversation, conducted in body language.
10:26Their relationship is sealed, touchingly.
10:50Crocodiles are extremely sensitive to touch.
10:53Their armour-plated toughness would appear to be only skin deep.
11:05Such complicated language and behaviour is exceptional among today's reptiles.
11:11But crocodiles might provide a tantalising rear window
11:14on the social life of their ancient relatives, the dinosaurs.
11:22Nile crocodiles are the most fraternal crocs of all.
11:27Once a year they hang out together, soaking up the sun at traditional mating places.
11:34These are far from being lazy afternoons.
11:37The group is very organised, so individuals keep a careful eye on movements within it.
11:44An adult male, over five metres long.
11:48The centre of attention.
11:59Up to ten females spend much of their time in the water soliciting him.
12:05They bare their throats as a gesture of appeasement.
12:14Body signals are also used by the male.
12:17He shows off with noisy water displays.
12:35These postures enhance his attractiveness to females.
12:49It's they who often take the lead, by rubbing themselves along the length of his body.
13:10At first, he snubs both of them.
13:13But the rubbing releases a pungent oil from glands under their jaws.
13:19Both sexes are highly sensitive to this crocodile perfume.
13:23And the male answers with his own musky message.
13:36The scent in the water is particularly potent prior to mating.
14:13Several weeks later, the females are ready to make their nests.
14:19Even when basking, adults rarely move far from water.
14:23So it's ironic that the first and most critical part of the crocodilian life is spent on land.
14:34Crocodile babies are born encased in eggs.
14:37But they must still breathe air.
14:39It's essential that this mother lays her clutch well beyond the high water mark.
14:55The eggs will be so at risk from drowning, from predators and from temperature fluctuations,
15:01that she relies on exactly the same nest position year after year.
15:07These time-honoured sites are a measure of the experienced care that crocodile mothers provide.
15:20Once the excavation is complete, she lays her eggs in a trance-like state.
15:25She's entering a deep commitment to her offspring.
15:45The hole will become an incubator.
15:48Crocodile eggs will only develop if they remain between a steamy 27 and 34 degrees.
15:56So her choice of site is critical.
16:09Nest chambers from equatorial African plains to high Himalayan river valleys
16:14all remain within this temperature range.
16:17But no one knows how crocodile mothers get it right.
16:30Once the nest is sealed, the mothers keep vigil for 90 days.
16:44Temperature determines the sex of the developing eggs.
16:48A half-degree difference between the top and bottom of the nest
16:52could markedly affect the ratio of males to females.
16:56Given the changes in climate that the world has experienced,
16:59it seems incredible that crocodiles have survived at all.
17:03It seems incredible that crocodiles have survived at all.
17:28Raiders might be drawn to their combined noise and smell.
17:33Hopefully, their mother will hear their calls and reach the nest first.
17:46the cavalcade.
17:53The keys will fill.
17:57it was such a twisted animal.
18:05Warpedalım, where he lost.
18:06Once she digs them out, they must reach the relative security of water as quickly as possible.
18:20The babies could probably find their own way, but they're only safe if they all stick together.
18:26So their mother transports them to water herself, in her mouth.
18:42The skin of her lower jaw stretches into a hanging cradle, in which she can carry fifteen or so at
18:49a time.
18:52It's a snug fit, once you're in.
19:02Her forty or so eggs hatch simultaneously, so she'll have to make several trips.
19:23The clamourings of the waiting hatchlings constantly remind her to return to the nest.
19:37And ensure that no one misses the last bus.
20:02She releases them into a nursery pool, where they must make the most of her tender loving care.
20:08They have only a few weeks under her watchful eye.
20:19For safety's sake, they call to each other, and to her, conversations which continue into adulthood.
20:26The eighteen different sounds they'll use represent a vocabulary more typical of mammals than of reptiles.
20:38Unlike mammals, their rate of growth is affected by temperature.
20:42The warmer it is, the quicker the food digests into body bulk.
20:46Over a lifetime under a tropical sun, they may grow four thousand times bigger than this.
21:02Their mother won't eat at all.
21:05She's protecting her infants from being eaten, even by other crocodiles.
21:09The tworegionaries.
21:20Who is the man who be dressed as aKapi-ил?
21:27Who is the Mars?
21:38They are not missing.
21:39The animals.
21:47The mother successfully defends her own brood, but it's a grim reminder that crocodiles will eat just about anything.
21:58Her babies will learn that successful crocodiles take all their dietary chances.
22:04Their hunting technique is there from birth.
22:07With eyes, ears and nose at water level, they mirror the tactics they'll use as adults.
22:56These shoreline snacks may be wildebeest or zebra in years to come.
23:30They will lie on common ones.
23:32They are living to survive this tender age, but competition between the youngsters is intense.
23:38Despite their mother's protection, only 2% of them will survive.
23:54The babies of Cayman, a type of South American crocodile, face even shorter odds.
24:02Wildlife may seem abundant in their Venezuelan marsh, but that's because the water elsewhere is drying up.
24:11Even the fish are out of water.
24:18The dry season is five months long, but in some years it's more severe than usual.
24:25Unexpectedly, animals can be left high if not exactly dry.
24:46Eventually, some of these watercourses will dry up completely, leaving many Cayman exposed and dehydrated.
24:58Temporary skin relief is provided by this ultimate of face packs.
25:03Mud is an effective crocodilian sunscreen.
25:12Cooling water is at a premium.
25:15The remaining pools are becoming overcrowded.
25:21At such pressing times, the adults usually rub along.
25:25However, babies could be eaten by them, so this is no place for a mother to raise her young.
25:37Fortunately, her babies can expect complete maternal detention during this five-month period of danger.
25:53The shrinking watercourse becomes increasingly hazardous for the babies.
25:58Drastic measures are called for.
26:08Night-time cameras reveal that they will make a run for it under the cover.
26:12of dark.
26:19That escape will be risky, for it's made over land.
26:24Mother leads the way.
26:37It's a while before the babies have the courage to join her.
27:03Calls of reassurance, and maybe her musky smell, encourage the hatchlings out of the water.
27:34She follows good instincts.
27:37Night-time temperatures are less dangerous.
27:39Night-time temperatures are less dangerous.
27:39to tiny, cold-blooded bodies, and there are fewer threats about.
27:43But this is a long march that must be concluded by daybreak.
27:48saat-time temperatures are almost terrible.clamation
28:17of the tragedieskmale can realize it is but it appears it also was very rare, animals
28:17of mondos can never sit before the mortality Mafal wiele
28:21Their mother's acute sense of smell brings them to their watery destination, with less
28:27than an hour to spare.
28:45There's plenty of water here for her babies to survive the rest of the dry season.
29:02But lots of other female caiman have had the same idea, and there's only room for one adult.
29:09The mothers must fight, or, as is more often the case, they simply leave.
29:17Their offspring are far from abandoned.
29:20The remaining female will adopt and protect them all, over 100 of them.
29:35This super mum carries her burden lightly.
29:42Family life may be unconventional, but crocodiles do grow up in company.
29:47As hunting adults, this may prepare them for dedicated teamwork.
30:01Especially if there's a rare dish on the menu.
30:10Migrating zebra cross the Mara River in Kenya on only a few occasions each year.
30:18Resident Nile crocodiles cannot afford to miss these fleeting chances, so they cooperate.
30:26From different places under the river banks, they spend days waiting and watching the nervous
30:31herds.
30:32those who wanted to I saw the mass night.
30:37ollaan
31:04Only when the zebra have committed themselves
31:07to a departure point, do the crocodiles take up their final positions.
31:22The current drags the zebra downstream,
31:25so five or six crocodiles cover the crossing from different angles.
31:35It's hard work for crocodiles too, but they can submerge,
31:39taking advantage of deeper, slower colors to move closer.
31:55Their approach is stealthy, measured and tactical,
32:00as if moving in on a chosen victim.
32:38The current is flowing in this zebra's favor.
32:41It buffets the crocodiles out of the sea.
32:57The zebra's wide rump gives it a big advantage.
33:08The zebra's wide rump gives it a big advantage.
33:17I don't know.
33:38Adult zebras also have a vicious kick,
33:41which could break a crocodile's jaw.
33:43That might mean starvation, so crocodiles are also taking risks.
34:07A lot of effort results in little success for the crocodiles,
34:11but only until smaller, more vulnerable animals enter the water.
34:20At any time, the zebras can be ambushed by frightening power
34:31and lightning speed.
34:38The baby zebra faces several waves of attack.
35:04This is the advantage of teamwork.
35:19Most of the year, life along Africa's rivers is even more of a struggle.
35:29The dry season in Zambia's Luangua Valley can be unsparing.
35:50Even vegetarians are forced to scavenge.
36:11But crocodiles still thrive on the edge.
36:27Far from being dependent on large mammals such as wildebeest or zebra,
36:31crocodiles have extraordinarily adaptable diets.
36:35We've not known this until now because we've never seen them hunting at night.
36:46What crocodiles do at night has remained a mystery
36:49because they will only move around naturally in total darkness.
36:53So only with the use of invisible infrared light can we see their nocturnal habits for the first time.
37:04In the Luangua River shallows, a Nile crocodile hunts for less glamorous prey.
37:09It's stalking fish.
37:12It's stalking fish.
37:22I don't know.
37:42Over the year, crocodiles fatten up on fish and mollusks rather than mammals.
37:55Mammals come and go, but the muddy river bottom is always a good place to stir up snails,
38:02for instance.
38:11The crocodile is a flexible feeder in its methods, too.
38:16It uses its armour-plated body as sinuously as the length of fishing net to corral fish
38:23towards the shore.
38:24I don't know.
38:56Within their element, crocodiles equally deserve the title King of the Beasts.
39:20Only when the dry season becomes desperate are these two great hunters of land and water
39:26likely to come face to face.
39:43But only the crocodile is bold enough to leave the safety of water and meet the lion on its
39:49home ground.
39:55ground.
40:07I don't know.
40:34Few animals would actively take on a whole pride.
41:16The lions are simply frustrated.
41:24Especially when the smell of their supper coaxes other crocodiles out of the water.
41:57There's a lot of people in the water.
42:09Crocodiles have thick skins.
42:11The lions are forced to defend their meal by moving to a different table.
42:19They leave nothing but scraps behind.
42:44The reptiles have stronger stomachs than the mammals.
42:48Lions can only cope with the chewy parts.
42:50Crocodile-digested juices are so acidic that they can break down skin, bone and horn to
42:57be turned into muscle.
43:04There's no such thing as crocodile leftovers.
43:14Their exceptional sense of smell enables them to capitalise quickly on the demise of others.
43:20And at the end of the dry season, the smell of death is everywhere.
43:31A mother hippo mourns her baby.
43:37Crocodiles have good reason to be wary of adult hippos, so they wait for the grieving mother
43:42to go.
43:57Food, any food, is hard to find.
44:01Crocodiles from up to seven kilometres away recognise the whiff of opportunity.
44:20One dead hippo attracts over one hundred hungry crocodiles, but there's no feeding frenzy.
44:42The reason for this patient approach?
44:46Crocodiles have a powerful grip and sharp teeth.
44:49But their jaws don't move sideways, they can't chew.
44:56So they have to eat large animals together.
45:00One or two crocodiles effectively brace the carcass in their jaws, while others wrench off smaller
45:06pieces of flesh by spinning their bodies around.
45:16Everyone waits their time.
45:18Everyone waits their time.
45:18Everyone waits their time.
45:40With such tolerant table manners it might take 24 hours to satisfy the whole queue of diners.
45:47water
45:48Voilà it, man.
46:28The End
46:46Too readily, perhaps, we have cast crocodiles as ruthless predators, when they're also well-mannered, adaptable creatures.
46:57And too readily, we have called them primitive, when our own human design has yet to stand up to their
47:05successful test of time.
47:08In evolutionary terms, the crocodile has every reason to smile.
47:31The End
47:40The End
47:49The End
47:50The End
47:54The End
47:54The End
47:55The End
47:55The End
47:57The End
47:58The End
47:59The End
48:01The End
48:01The End
48:01The End
Comments