Crocodiles - The Whole Story S01E05 - The Secrets of Nature

[Music] [Music] hello [Music] [Music] hey [Music] long ago when animals ruled the world africa was a very different place all the animals understood each other and got along peacefully in the calm waters of a lake lived the crocodile every evening he would crawl out of twilight and his smooth beautiful skin glowed in the light of the moon one night a curious frog saw this beautiful creature overalled by his glowing skin he croaked loud praises soon all the other animals came to gaze at the crocodile herds of zebra and kuru arrived to admire him where he basked on the bank [Music] crocodile saw their admiring looks and he became vain and each day he crawled out a little earlier to enjoy their admiration for longer but as he did nothing but lie there they eventually went away bored the hot sun began to dry his beautiful skin and it grew hard and greenish and bumpy and scaly covered in shame crocodiles slunk back to the water to hide his once lovely body he'd paid a high price for vanity and to this day crocodile blames frog for his misfortunes if ever he hears one croak he silences it with a snap of his jaws crocodiles are the world's largest reptiles they look like a relic of the dinosaur days and indeed their family is very ancient one of the oldest on earth reptiles come in all shapes and sizes from desert dwellers like the leopard tortoise of the kuru in south africa's cape province to this boa constrictor which lives in the hot wet world of the madagascan rainforest most reptiles have dry rough scales but that's one of the few external characteristics they share otherwise they could hardly look more different this chameleon is just one member of a family that has nearly seven thousand distinct species some reptiles are sea creatures like the green turtle most reptiles live permanently on land but crocodiles divide their time between land and water though they're the biggest of the reptiles not all are large of africa's three species the west african dwarf crocodile rarely grows longer than two meters both it and the slightly larger long-snouted crocodile are rarely seen hiding away in forested swampy regions of the same part of africa a long thin snout can slash through water and catch prey with ease but it works just as well against land animals [Applause] the nile crocodile is africa's largest and best known lay three tall men end to end and put the weight of 14 together and you have a big nile crocodile and though its brain is the largest in the reptile world it's still only the size of a thumb crocodiles are designed for water where they can breathe see smell and hear while almost totally submerged their nostrils have valves that open and shut so water doesn't rush into their lungs sometimes they're the only bit of the crocodile visible above water eyes that look like a snakes have three sets of eyelids top bottom and an inner set the nictitating membranes the nictitating membranes keep the eyes moist and clean but they're also somewhat like a diver's goggles for underwater work a crocodile's ears are the sharpest of any reptile with movable ear flaps that work like a loudspeaker volume control short stubby legs end in webbed back feet for steering and paddling in water and blunter front feet for climbing banks and digging crocodiles have no lips even with jaws clamped shut water leaks in however plumbing problems are solved by a special pallet at the back of the throat this shuts on submersion to keep the crocodile watertight crocodiles can't chew their lower jaws only move up and down not sideways so they must pound and crush their food and they can't keep their toothy traps shut without physical effort they just spring open naturally when they're relaxing gaping also helps them cool off a crocodile's jaws pack immense power and 66 teeth interlock like a zip fastener the combined strength of both can crush a big animal like a car wrecking machine the word crocodile comes from the old greek crocodrilos pebble worms worm hardly described this big reptile but in medieval times it also meant dragon much more suitable for an animal as scaly as that mythological monster crocodiles can live to a hundred years during that time they never stop growing just keep getting bigger and bigger that scaly tale is never used to knock prey off its feet contrary to popular myth it's a propeller and is one of the distinctive characteristics that make the crocodile a supremely designed predator with almost no natural enemies [Music] from day one a crocodile learns that scales and bumps make you look remarkably like a log just lie quite still and your meals will be completely fooled even if they tickle don't bat so much as an eyelid [Music] [Music] from small mules big crocodiles grow and naturally appetites too the true heavyweights of the nile crocodile world live in east africa each year on long annual migrations huge herds of zebra and wildebeest must fold rivers full of crocodiles crocodiles lie quietly in ambush but here there's no need for these huge reptiles life can be literally feast or famine and migrations are feast days right most cross safely some just make it but others never reach the opposite bank [Music] here on the serengeti plains the catchers are big enough to keep several crocodiles busy very few reptiles hunt and eat together but crocodiles do between april and may each year breen migrate up river and dumu on the south african border with mozambique and the crocodiles line up in toothy welcome even tiddlers are worth filtering a light snack before the main course other fish fanciers know of this eating place [Music] maybe not the right dining companion for a marsh terrapin a curve of crocodile tails creates a solid fishnet at last the main course big fat breed this looks as hard as fishing in a barrel when the breen migrate there's usually plenty for everyone and peace reigns but a particularly juicy fat catch might spark envy wiser to go off to a quiet corner and eat alone crocodiles often swallow meals whole an acid bath of digestive juices quickly liquidizes them it's as powerful as car battery acid and can even dissolve bone whole or partially shredded but never rotten crocs like their food fresh [Music] for 180 million years dinosaurs and flying reptiles ruled the earth until nearly all of them vanished 65 million years ago but of the great arkasaur dynasty to which tyrannosaurus rex belonged one line has survived the crocodilia today's amphibious crocodiles descended originally from a land animal terrestrisukus that lived about 240 million years ago in europe it was perhaps the size of a large domestic cat with long legs and short claws for easy running its skin was probably rather like a modern crocodiles then about 200 million years ago the protozoukians arrived on the scene they also lived on the land their belly scales were fused into a protective shield like today's tortoises and two rows of plates defended their spine but their legs were shorter and their skulls and jaws longer than terrestrial [Music] sugars about 140 million years ago the ancient crocodilians changed their lifestyle and turned amphibious some even took to the sea these miso sukins looked much more like today's crocodiles they had large webbed back feet and long narrow jaws to help them catch invertebrates and fish modern crocodiles evolved 80 million years ago when warmer climates brought greater diversity and size some were huge then a fossil found in texas was 15 meters long the skull alone measured 2 meters aptly named terrible crocodile it weighed as much as a bus would have stood as high as an average ceiling and was as big as tyrannosaurus rex 80 million years ago the family had already divided into two branches the alligatorines and the crocodilians generally an alligator is smaller than a crocodile its snout is rounded and shovel-shaped a crocodile's is v-shaped and its upper jaw is wider than the lower and overlaps it completely when it's shut there are only two types of alligator the american and the chinese and alligators and a crocodile's design is so well suited to its lifestyle that in the last 80 million years it's hardly changed at all hard to believe but this sharp-toothed animal shares certain of its features with birds such as a muscular gizzard to crush food before it goes into the stomach crocodiles also make nests but they're very different structures from the average bird's nest way back over 300 million years ago the ancestors of both crocodiles and birds were elated perhaps today's secretary bird can give us clues as to how the extinct archosaurs lived it's a fast-moving predator that eats small land animals and it probably hunts and moves in much the way the ancient reptilian dinosaurs are thought to have done [Music] as crocodiles have changed so little in the last 80 million years perhaps a closer study of them might explain why dinosaurs existed for so [Music] long [Music] a crocodile leads a straightforward life eat sleep lie in the sun the sun kick-starts its day a cold-blooded animal needs solar energy to raise its body temperature for this reason most crocodiles live in the tropics and subtropics at low altitude and in slow-moving warmer water in places which fish-eating birds flock to even on some oceanic islands like basaruto off the coast of mozambique there are crocodiles the pioneers would have had to cross the open sea to reach this idyllic place behind huge dunes are the crocodile's essential fresh water supplies crocodiles are also partial to mangrove swamps easy to hide in good for food a band of tropical rainforest lies along the coast of west and central africa this is slender-snouted crocodile territory it hunts on land as well as in the water but has no hope of catching a distant relative which can take to the air the greatest and lucia wetlands of south africa's east coast are the continent's richest here where jakana's tread the lily pads and white pelicans congregate is a 20 kilometer tidal causeway linking a huge lake to the indian ocean it's the only place on earth where three of the most dangerous aquatic animals share the same waters sharks crocodiles and hippos there are also multitudes of water-loving birds lured by huge populations of invertebrates and fish frogs and crabs it's a busy place [Music] man [Applause] [Music] pelicans lift wings in unison to shade the surface and pinpoint the fish in a synchronized roundup cormorants synchronize their panting [Music] and a pied kingfisher is challenged by a big catch frothy pink and white flamingos pay scant attention to a crocodile the waters crawl with him one of south africa's largest crocodile populations lives here this is one animal for whom sunbathing is good it can't function without the sun and needs a daily dose to keep going a crocodile uses the temperature difference between land and water as the thermostat that adjusts its central heating system regularly traveling between the two to keep its temperature steady and soaking up the sun as it needs it like all snakes the gaboon viper is also a cold-blooded creature that must have sun to stay warm and survive lizards likewise crocodile waters are usually also hippo waters the two normally maintain a state of uneasy truce but sometimes the hippos deliberately break it these are extremely dangerous herbivores some crocodiles are eating a freshly killed nyala spinning their bodies to rip chunks of flesh since they cannot bite it off but a female hippo has taken exception to the spectacle and seems to want to break it up not one of the crocodiles could match her for size or strength and they leave her be even though some are lying in the water right beside her they outnumber her but she ignores them and makes for their favorite basking place but what makes her sniff their territory is she familiarizing herself with the smell of the enemy is she challenging their right to this territory her entire behavior is an assertion of dominance or she may be protecting a young hippo calf not far off but equally she could have been distressed by the crocodile's kill hippos are believed to murder another mammal's death just exactly as elephants do um [Music] even though their brains are relatively small crocodiles have evolved complex and sophisticated ways to communicate this is mostly subtle sound body language smell touch and special vibrations all make up crocodile talk [Music] at the mating season gets off to a noisy start with power struggles between rival males now perhaps is peak communication time it's a race to breed and everyone's going for broke with a toothy lear a big male begins to court and he uses a range of tactile and vocal signals to help him he slaps his head on the water to show dominance and he blows seductive bubbles and vibrates his body so the water jumps in what's called a finger dance but the females aren't paying attention they're fighting to be first to mate since there are not many males of his caliber around [Music] and one of them has fought off her rival in this part of the reptile world it's usually female who pursues male he just needs to make the slap bubble and vibration moves which are the prelude to mating once he's mated his sperm may have to continue a hidden power struggle racing to outswim the rest and reach the eggs first because he won't be the only partner she's had she's mated with several sampling the best male wears on the market to secure the best jeans for her future young she may be sharing an intimate moment with one male but she won't refuse a newcomer who's arrived to prise her away obviously discretions hardly sacrosanct in a crocodile's world [Music] what is sacrosanct to a female crocodile is her young when it comes to them she shows what good parents are made of most reptiles just lay their eggs then push off and leave them to get on with it but not her being a good parent mostly means being a bodyguard and you could hardly find a more intimidating one than this great scaly creature she's a serious enemy deterrent several months after mating she digs a nest by the water not too close or it could flood nor too far her hatchlings mustn't have to cross too much open ground soft shelled when first laid her eggs are roughly the size of a ducks there are other females in the vicinity this bank is a crocodile maternity ward not always a peaceful one and one which the enemy has honed in on she's finished laying and covers her eggs with a warm soil blanket how warm this is will be crucial to their future so will camouflaging the nest and then she stays on guard hardly stirring from her post three long months later her eggs are hatching at the very first squeak of life mother makes a beeline for her hatchlings the tiny creatures need their big maternal bodyguard now more than ever because their cries have given them away they need to be escorted to the water and mother a crocodile armored car is going to do it jaws and teeth that can crush a buffalo to pulp won't even scratch them not quite a full cargo room for a few more in her special mouth pouch first though the late hatches need a hand as she digs the vibrations stimulate them to get cracking and come out to her naturally her throat valve is closed now otherwise some babies might travel the wrong way full up and off to the water but someone else in this ward is blocking the corridor because of mother's digging more hatchlings are emerging breaking out with a temporary egg tooth on the tip of the snout a small growth that soon disappears the hatchlings began their race for life in the egg with its limited oxygen supply suffocation could have been the penalty for delay the sex of most animal embryos is fixed from the very moment of fertilization but remarkably it's an external force that has a determining role in whether male or female climbs from a crocodile egg temperature and equally remarkably temperature also helped design their skin markings down in the water mother gently shakes her mouth for free into their nursery it's close to the bank full of tall grasses and reeds to hide in but this is an alarming place for something so tiny an armor-plated back feels and is far safer however a water monitor is sneaking up on the nest site in her absence this is just what she was trying to guard against but it's after eggs they were about to hatch they never will now [Music] even though their mother does her best only about two percent of her clutch will reach adulthood a crocodile's early years are the years of living dangerously [Music] crocodiles are designed for water and that's where they move with greatest ease powered by an undulating tail nearly half its body length a crocodile can cruise easily at 15 kilometers an hour with legs tucked close to its sides to make it streamlined most of their time in water crocodiles just take it easy keeping still saves energy and why waste it if you don't have to they paddle hardly at all to keep nose above water the air in their lungs keeps them afloat without having to work legs too hard oxygen is fuel and when a crocodile goes under its heart may slow to just four beats a minute to conserve this precious resource slowing its metabolic rate enables it to stay down a long time and it may swallow stones to help temperature plays a key role too the colder the animal the lower its metabolic rate some have actually held their breath for a staggering two hours a crocodile is a living oxygen tank that should be the envy of human divers crocodiles look cumbersome out of water they are capable of short bursts of speed but mostly they go slow and steady on land rolling their way to their destination this is the classic crocodile walk the leisurely belly crawl or perhaps slinky hip wiggle like holiday makers crocodiles leave their swimming pools in order to soak up the sun once settled they hardly budge crocodiles have one special walk unique among reptiles the high walk it's more like a mammals with legs positioned almost straight under the body it's the best way to clamber over other sunbathers without upsetting them but exercise tires a crocodile because it quickly builds up high levels of lactic acid in its blood so after a major workout by catching prey a good rest is just what's needed for general well-being so the levels can drop [Music] [Music] it's always best to let sleeping crocs lie they are not trustworthy neighbors they can be snappy you don't want to put a foot wrong [Music] it pays to have wings to keep out of reach however life with these unpredictable creatures does have its plus side they churn up the mud and outwiggles bird food hanging around a crocs pool also has benefits for homemakers a sharp-toothed reptilian submarine is a first-class predator deterrent however almost nothing in life comes free nesting birds may benefit from a crocodile's unwitting protection but the protection racketeers exact their fees this is not a cheap nest site the fee can be high some nestlings pay the ultimate price to the protection gang a golden rule never fall off the patch there is one animal that seems somehow immune to crocodile attack the water buck pungent body odors that waft crocodile with make them keep their distance this antelope can enter the water apparently without fear it's not crocodiles but these animals which are the greater enemy of humans in africa and they're one of the few creatures a crocodile actually avoids especially in the mating season two big male hippos go into battle with their teeth which are like swords to them sex is a serious issue they may battle for days with the loser losing more than the fight the crocodiles watch from a safe distance the outcome may interest them teeth as long as a human forearm have inflicted terrible wounds the loser's entire body is slashed the defeated male is so badly hurt he has trouble even moving a young male tries to lick his wounds clean perhaps there's an instinctive spark of fellow feeling towards another male [Music] his efforts don't appear to be having any effect at all [Music] weeping none of the famous tears a crocodile watches the drama to its last act he can't last long now the wounds are too deep and already the carnivores are starting to move in [Music] one last breath he's gone with nothing to fear now from its traditional enemy the first crocodile tests the corpse for somewhere to bite [Music] many will feast on the fallen hippo and when the crocodiles can eat no more crabs birds and other scavengers will take over [Music] the crocodiles of africa's wild places have a great number of competitors and an even greater variety of prey over millions of years these two factors have honed them into versatile opportunistic hunters master predators old as the dinosaurs a legacy from the days of tyrannosaurus [Music] rex i [Music] [Music] i saw me i [Music] am you

Channel: The Secrets of Nature

Views: 101,854

Rating: 4.7293234 out of 5

Keywords: orf universum, documentary, blue chip, natural history, secrets of nature, planet earth, natura, naturaleza, documentales, wildlife, grandes documentales

Id: HF7XhLgjsT0

Length: 50min 3sec (3003 seconds)

Published: Tue Oct 13 2020