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  • 5/31/2025

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00:00I
00:30I don't know.
01:00Crocodiles hailed from the great age of reptiles well over 70 million years ago.
01:09Since then, the world has changed dramatically around them, but amazingly, they have changed little.
01:18They're the only great reptile predator to have outlived the dinosaurs.
01:29Ancient they may be, but 70 million years on, they're still the most successful freshwater predator.
01:37Most of the waterways in the tropics these days have their own species of crocodile.
01:42How 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 since.
01:54This film reveals the nature of that success.
02:08Crocodiles may have scored an early evolutionary bullseye, but there's much more to their staying power than brute strength.
02:16Crocodiles may have scored an early evolutionary bullseye.
02:20Only now, by exploring their complete world, above and below water, by day and night, can we fully appreciate just how sophisticated they are.
02:40Underwater crocodiles have been so far.
03:08Underwater crocodiles have perfect poise.
03:11They can control their buoyancy like a submarine.
03:17To dive, they just breathe out, which reduces their lung volume.
03:21They can sink without trace.
03:35While submerged, a protective membrane closes over their eyes, like swimming goggles.
03:46Crocodiles are cold-blooded.
03:49They rely on the temperature of the sun and water to heat themselves up or to cool down.
03:54But when fully charged, they're capable of breathtaking power and speed.
04:09They're the most dangerous freshwater predator on the planet.
04:24Even Tyrannosaurus rex couldn't match this winning formula.
04:32It's a design that has allowed them to spread around the tropical world.
04:39This extended family includes alligators of temperate waterways.
04:46Garils of the Indian subcontinent.
04:50And caiman of tropical South America.
04:52They've even invaded the sea.
05:07Crocodiles have special glands which enable them to tolerate salt water.
05:11This is how they've colonized new rivers along the coast.
05:14But only a few species can migrate across oceans.
05:29The real specialists, the saltwater crocodiles, are affectionately known as salties.
05:35They've been seen 1,000 kilometres from land encrusted with barnacles as they search for new island homes.
05:46This pioneering spirit and their unique character has made them a universal threat.
06:05Crocodiles deserve their tough reputation, but they aren't just solitary killers.
06:20In the calm of the Florida swamps, we can begin to see them in a new light.
06:35They are reptiles with social skills.
06:38And American alligators are particularly chatty.
06:41During the breeding season, an expressive chorus of bellows, grunts and hisses rises from their densely vegetated swamps.
06:57The males are calling to distant females.
07:00But their bellows sometimes attract rivals.
07:12There are snappy ways to make your feelings known if you end up in the wrong company.
07:22The resident male only shows a bit of muscle if the rival fails to get the message.
07:27He's made his point, and he can now focus on finding a mate.
07:48Vibrations within his muscle walls send sound waves rippling out into the swamp.
08:03Powerful enough to make the water dance.
08:05You can now focus on making them fly rushing at three per fifty different species.
08:08It is about a dry life, as it allows them to...
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08:31Part of his roar radiates at such low frequency that human ears can't hear it.
08:38But these subsonic crawls have astounding penetration,
08:43travelling four times faster and further under the water.
08:48Only with special low-frequency recordings can we appreciate what the female alligator hears.
09:01She finds his romantic rumblings irresistible.
09:31Speed, speed, speed.
09:53Even though the call may come from the remotest parts of the swamp, she is soon on his wavelength.
09:59Then they have a more intimate conversation, conducted in body language.
10:05Their relationship is sealed, touchingly.
10:17Shhh, shhh, shhh, shhh.
10:26Their relationship is sealed, touchingly.
10:29Shhh, shhh, shhh.
10:45Shhh, shhh.
10:47Crocodiles are extremely sensitive to touch.
10:52Their armour-plated toughness would appear to be only skin deep.
11:04Such complicated language and behaviour is exceptional among today's reptiles,
11:09but crocodiles might provide a tantalising rear window
11:13on the social life of their ancient relatives, the dinosaurs.
11:21Nile crocodiles are the most fraternal crocs of all.
11:25Once a year they hang out together, soaking up the sun at traditional mating places.
11:37They stay around for several weeks until the mothers are ready to make their nests.
11:43Even when basking, adults rarely move far from water,
11:50so it's ironic that the first and most critical part of the crocodilian life is spent on land.
12:01Crocodile babies are born encased in eggs, but they must still breathe air.
12:06There, it's essential that this mother lays her clutch well beyond the high watermark.
12:11The eggs will be so at risk from drowning, from predators and from temperature fluctuations,
12:29that she relies on exactly the same nest position year after year.
12:33These time-honoured sites are a measure of the experienced care that crocodile mothers provide.
12:47Once the excavation is complete, she lays her eggs in a trance-like state.
12:52She's entering a deep commitment to her offspring.
12:56The hole will become an incubator.
13:16Crocodile eggs will only develop if they remain between a steamy 27 and 34 degrees.
13:22So her choice of site is critical.
13:37Nest chambers from equatorial African plains to high Himalayan river valleys
13:41all remain within this temperature range.
13:44But no one knows how crocodile mothers get it right.
13:58Once the nest is sealed, the mothers keep vigil for 90 days.
14:03Temperature determines the sex of the developing eggs.
14:16A half degree difference between the top and bottom of the nest
14:19can markedly affect the ratio of males to females.
14:23Given the changes in climate that the world has experienced,
14:26it seems incredible that crocodiles have survived at all.
14:30Overall, enough males and females emerge.
14:50But these baby Nile crocs face more immediate threats to existence.
14:54Raiders might be drawn to their combined noise and smell.
14:59Hopefully their mother will hear their calls and reach the nest first.
15:03fairy Nile crocs face more visually,
15:10fairyNAwer tips of the nest.
15:12Here, the bird will reach the nest first.
15:14M constructionon, the nile crocs are the same as a bird and when the animals are in nature.
15:16No, Deshalbate by the bird legs and the females are in nature.
15:18He will follow the name of the tail of the birds and a bird.
15:20Once she digs them out, they must reach the relative security of water as quickly as possible
15:38The babies could probably find their own way, but they're only safe if they all stick together
15:53So their mother transports them to water herself, in her mouth
16:08The skin of her lower jaw stretches into a hanging cradle, in which she can carry 15 or so at a time
16:19It's a snug fit, once you're in
16:29Her 40 or so eggs hatch simultaneously, so she'll have to make several trips
16:38The clamourings of the waiting hatchlings constantly remind her to return to the nest
16:56and ensure that no one misses the last bus
17:26She releases them into a nursery pool, where they must make the most of her tender loving care
17:35They have only a few weeks under her watchful eye
17:38For safety's sake, they call to each other, and to her, conversations which continue into adulthood
17:53The 18 different sounds they'll use represent a vocabulary more typical of mammals than of reptiles
18:00Unlike mammals, their rate of growth is affected by temperature
18:09The warmer it is, the quicker the food digests into body bulk
18:13Over a lifetime, under a tropical sun, they may grow 4,000 times bigger than this
18:19Their mother won't eat at all
18:32She's protecting her infants from being eaten, even by other crocodiles
18:36And Amikou.
19:01The mother successfully defends her own brood,
19:18but it's a grim reminder that crocodiles will eat just about anything.
19:25Her babies will learn that successful crocodiles take all their dietary chances.
19:31Their hunting technique is there from birth.
19:35With eyes, ears and nose at water level,
19:38they mirror the tactics they'll use as adults.
20:01These shoreline snacks may be wildebeest or zebra in years to come.
20:05These shoreline snacks may be wildebeest or zebra in years to come.
20:20These shoreline snacks may be wildebeest or zebra in years to come.
20:27They may be wildebeest or zebra in years to come.
20:34They rely on communal living to survive this tender age,
20:48but competition between the youngsters is intense.
20:52Despite their mother's protection, only 2% of them will survive.
20:58They rely on communal living to survive this tender age,
21:02but competition between the youngsters is intense.
21:05Despite their mother's protection, only 2% of them will survive.
21:10The babies of Cayman, a type of South American crocodile, face even shorter odds.
21:29Wildlife may seem abundant in their Venezuelan marsh,
21:32but that's because the water elsewhere is drying up.
21:36Even the fish are out of water.
21:46The dry season is five months long,
21:48but in some years it's more severe than usual.
21:51Unexpectedly, animals can be left high if not exactly dry.
22:06Eventually, some of these watercourses will dry up completely,
22:16leaving many Cayman exposed and dehydrated.
22:25Temporary skin relief is provided by this ultimate of face packs.
22:30Mud is an effective crocodilian sunscreen.
22:40Cooling water is at a premium.
22:42The remaining pools are becoming overcrowded.
22:49At such pressing times, the adults usually rub along.
22:52However, babies could be eaten by them,
22:54so this is no place for a mother to raise her young.
23:04Fortunately, her babies can expect complete maternal detention
23:07during this five-month period of danger.
23:09The shrinking watercourse becomes increasingly hazardous for the babies.
23:24Drastic measures are called for.
23:26Night-time cameras reveal that they will make a run for it,
23:39under the cover of dark.
23:47Their escape will be risky,
23:49for it's made over land.
23:51Mother leads the way.
23:53It's a while before the babies have the courage to join her.
23:55It's a while before the babies have the courage to join her.
24:08It's a while before the babies have the courage to join her.
24:10It's a while before the babies have the courage to join her.
24:11It's a while before the babies have the courage to join her.
24:30Calls of reassurance, and maybe her musky smell,
24:33encourage the hatchlings out of the water.
24:36She follows good instincts.
24:38Night-time temperatures are less than an air.
24:40It's a while before the babies are still in the water.
24:41It's a while before the babies have the courage to join her.
24:42The birds have the courage to join her to join her.
24:46She follows good instincts.
24:48Night-time temperatures are less than a very high heat.
24:51She follows good instincts.
25:04Nighttime temperatures are less dangerous to tiny cold-blooded bodies
25:08and there are fewer threats about.
25:11But this is a long march that must be concluded by daybreak.
25:21It's a long march.
25:51It brings them to their watery destination with less than an hour to spare.
26:12There's plenty of water here for her babies to survive the rest of the dry season.
26:21But lots of other female caiman have had the same idea and there's only room for one adult.
26:36The mothers must fight or, as is more often the case, they simply leave.
26:41Their offspring are far from abandoned.
26:48The remaining female will adopt and protect them all, over 100 of them.
26:52This super-mum carries her burden lightly.
27:09Family life may be unconventional, but crocodiles do grow up in company.
27:14As hunting adults, this may prepare them for dedicated teamwork.
27:29Especially if there's a rare dish on the menu.
27:32Migrating zebra cross the Mara River in Kenya on only a few occasions each year.
27:45Resident Nile crocodiles cannot afford to miss these fleeting chances.
27:51So, they cooperate.
27:52From different places under the riverbanks, they spend days waiting and watching the nervous herds.
27:59There are other staff in the internet trying to rebuild their needs.
28:22There's a lot of clothing here being used as being.
28:24Only when the zebra have committed themselves to a departure point
28:35do the crocodiles take up their final positions
28:49The current drags the zebra downstream
28:52so five or six crocodiles cover the crossing from different angles
29:02It's hard work for crocodiles too but they can submerge
29:06taking advantage of deeper slower currents to move closer
29:23Their approach is stealthy measured and tactical as if moving in on a chosen victim
29:38The current is flowing in the zebra's favour
29:41The current is flowing in the zebra's favour
29:54It buffets the crocodiles out of position and they can't get a grip
30:11The zebra's wide rump gives it a big advantage
30:27It's a big advantage
30:57Adult zebras also have a vicious kick which could break a crocodile's jaw.
31:11That might mean starvation, so crocodiles are also taking risks.
31:19A lot of effort results in little success for the crocodiles, but only until smaller,
31:40more vulnerable animals enter the water.
31:47At any time, zebras can be ambushed by fighting power
31:58and lightning speed.
32:05The baby zebra faces several waves of attack.
32:08This is the advantage of teamwork.
32:19Most of the year, life along Africa's rivers
32:37is even more of a struggle.
32:48The dry season in Zambia's Luangwa Valley can be unsparing.
33:03Even vegetarians are forced to scavenge.
33:18But crocodiles still thrive on the edge.
33:37Far from being dependent on large mammals such as wildebeest or zebra, crocodiles have extraordinarily
34:00adaptable diets.
34:02We've not known this until now because we've never seen them hunting at night.
34:11What crocodiles do at night has remained a mystery because they will only move around naturally in total darkness.
34:20So only with the use of invisible infrared light can we see their nocturnal habits for the first time.
34:30In the Luangwa River shallows, a Nile crocodile hunts for less glamorous prey.
34:36It's stalking fish.
34:39Over the year crocodiles fatten up on fish and mollusks rather than mammals.
35:07And it catches them in flexible ways.
35:16It uses its armor-plated body as sinuously as a length of fishing net to drive the fish towards the shore.
35:23Within their element crocodiles equally as the sea.
35:51Within their element crocodiles equally deserve the title King of the Beasts.
35:58only when the dry season becomes desperate are these two great hunters of land and water likely to come face to face.
36:13only when the dry season becomes desperate are these two great hunters of land and water likely to come face to face.
36:22But only the crocodile is bold enough to leave the safety of water and meet the lion on its home ground.
36:41and meet the lion on its home ground.
36:48and meet the lion and dt to live Columbia will perturb their fingers southwest them to feed the sea.
37:00and the water behind a sea.
37:03A few animals would actively take on
37:32the whole pride.
37:51The lions are simply frustrated, especially when the
38:21smell of their supper coaxes other crocodiles out of the water.
38:28A few animals would take a while.
38:35A few animals would take a while.
38:39A few animals would take a while.
38:43Crocodiles have thick skins, the lions are forced to defend their meal by moving to a different table.
39:13They leave nothing but scraps behind.
39:40While reptiles have stronger stomachs than the mammals, lions can only cope with the chewy parts.
39:47Crocodile digestive juices are so acidic that they can break down skin, bone and horn to be turned into muscle.
39:59There's no such thing as crocodile leftovers.
40:10Their exceptional sense of smell enables them to capitalise quickly on the demise of others.
40:17And at the end of the dry season, the smell of death is everywhere.
40:28Another hippo mourns her baby.
40:33Crocodiles have good reason to be wary of adult hippos, so they wait for the grieving mother to go.
40:40Food, any food is hard to find.
40:56Crocodiles from up to seven kilometres away recognise the whiff of opportunity.
41:01One dead hippo attracts over one hundred hungry crocodiles, but there's no feeding frenzy.
41:23This is crocodile queuing.
41:34The reason for this patient approach?
41:41Crocodiles have a powerful grip and sharp teeth.
41:45But their jaws don't move sideways, they can't chew.
41:52So they have to eat large animals together.
41:55One or two crocodiles effectively brace the carcass in their jaws,
41:59while others wrench off smaller pieces of flesh by spinning their bodies around.
42:05Everyone waits their time.
42:19With such tolerant table manners, it might take 24 hours to satisfy the whole queue of diners.
42:43Oliver Blackаж in the water has become a wild name.
42:49Oh, my God.
42:51I guess that they might mean that they need to be a medical condition.
42:54Over to three minutes, they have to eat large animals for three minutes.
42:58And they don't care about it.
43:00The French woman, they know that they are rare.
43:01They know that they're obvious.
43:02They don't care about it.
43:03This isn't until long.
43:04They never know that they're there.
43:05But in the end of the day, the reason they are unable to eat.
43:07They don't care about it, but it's impossible to eat.
43:09They don't care about it anymore.
43:42Too readily, perhaps, we have cast crocodiles as ruthless predators, when they're also well-mannered, adaptable creatures.
43:53And too readily, we have called them primitive, when our own human design has yet to stand up to their successful test of time.
44:04In evolutionary terms, the crocodile has every reason to smile.
44:11Next week, it's the leopard, and there's more wildlife on Sunday in BBC Two's Animal Zone at 5.25.
44:31Next night, here on BBC One, the National Lottery.
44:33First Day, here on BBC Two's Animal Zone
44:44Amen.