Turtles – The Fascinating World Beneath the Shell | Little Matters | Free Documentary Nature

Turtles are slow, calm, gentle creatures. But not always, and not all of them. Certain turtle species are fearsome hunters, while others, during mating season, become fierce fighters capable of killing. And still others are the sea's greatest voyagers or the world's most amazing time travelers. Some live hundreds of years. They can also hibernate or live buried underground for months before being born. Their shells could withstand a lion's bite, although that does complicate sex a bit. These incredible beings have been on the planet since before the dinosaurs appeared. The evolutionary race is a distance event, not a sprint. And the truth is that turtles are in the lead. Their hair is just a newcomer. The massive arrival of olive ridley sea turtles to lay their eggs on the beach, called an arribada, is one of the most magnificent spectacles in nature. It's difficult to explain, although we humans like to think that we understand everything. Every turtle or tortoise, no matter what the species, lives practically isolated from its fellows throughout its whole life. Turtles are tremendously solitary animals. And as far as we know, they don't communicate amongst themselves, they don't form defensive groups, nor do they eat together. The mating pairs don't even swim together in the sea except for the day that they copulate. Their isolation contrasts starkly with this impressive meeting. It's so punctual and geographically precise. What signal calls all these turtles into Ostional Beach in Costa Rica on the same evening? There are only three or four more beaches on the planet where similar landings take place. On the east coast of India. It must be instinct that makes them return to the place where they were born. They must have some sort of internal GPS navigator with that spot recorded on it for the rest of their lives. We don't have a theory that explains how they managed to synchronize their arrival so well. Because they can't have all been fertilized on the same day. We do understand their goal. In 40 or 50 days, depending on the sunlight, 10 million baby turtles will all crawl out of the sand at the same time. And since there are so many of them, not even the vultures that have flown in today to eat the eggs, but will come back with the seagulls when the time is up, not even they will be able to devour the immense tidal wave of little turtles returning to the sea. From August to November, four times a year, hundreds of thousands of Olive Ridley sea turtles crawl out onto the beach 10 days before the new moon to bury their eggs. This strategy does have a weak point. The multitudinous, synchronized hatching of all these eggs has a high cost in turtle lives. It's estimated that only half of the hatchlings will reach the water. And in the end, only 2 out of every 100 will manage to reproduce someday. Is such a sacrifice logical? It seems like a tremendous waste. But nonetheless, it's balanced so as to maintain a steady population. A female lays 100 eggs, so that if two hatchlings survive from each nest, statistically one male and one female, then the population will tend to stay stable. Losing 98% of the hatchlings is a tremendously savage natural event. It's a very elitist selection process. But that's how evolution works. With rare exceptions, turtles don't nest together. A nest often holds only 5 or 6 eggs buried close to the surface. Because the sex of each hatchling is determined as it develops by the temperature produced by the sunlight that falls on the layer of earth covering them. If the eggs are at a shallow depth and the weather is hot, more males are born. If the average temperature during incubation is low, then more females hatch. Although it depends in part on the weather, the species manages to keep a balanced ratio of males and females. The Spanish pond turtles have begun to hatch today. These members of the Moremes leprosa species have been closed up in their leathery shells for two months. They've been using the egg tooth that has grown on the tip of their nose to scratch away at the shell, little by little. This process can take 2 or 3 days. But turtles do everything slowly. And being born certainly isn't something you want to rush into. They're not in a hurry. They won't come out onto the surface just yet. They can't, because the soil on top of them is hard as a rock. They'll have to wait until it rains. Maybe a month, or maybe six months if it's a dry autumn. In North Africa and Western Mediterranean Europe, the territory of the Spanish pond turtle, the eggs laid in summer hatch in autumn if it rains. And if it doesn't, then after the cold winter, the hatchlings are forced to wait, buried alive. The Amazon river basin is home to one of the most evolved turtles on the face of the earth. It's so mimetic that it's hard to spot. Very few people know of it. But it's a highly skilled hunter, able to stalk without being seen. It moves very slowly, so slowly that no one notices its presence. That's the secret of the best predators. It hunts small, quick, living fish. Fish have a sense organ, the lateral line, that perceives all kinds of vibrations in the water. At this speed, and with this outward appearance, it looks like some lifeless thing slowly drifting in the current. Nothing gives it away. It looks like a piece of decaying wood weathered by time and the water. The growths on its skin break up its silhouette. Even some algae is attached to and living on its shell. A glance, a movement of its eyes, could alert its prey of the danger. But the eyes of a mata-mata are well camouflaged too. Disguised by the color of its skin. But this turtle's real secret weapon is its mouth. It works like a vacuum cleaner. When the mata-mata is hunting, its usual slowness suddenly turns into explosive speed. When it opens its jaws, it does it so quickly that it creates a current that sucks everything into its throat. A little fish that's close enough can't fight its pull. This movement is like a shot. The rest of the fish swimming nearby don't even detect it. Their instincts put them on maximum alert, but they don't know what they should be running away from, much less in which direction. They can't see the hunter's movements, so they don't recognize it. The mata-mata is an extraordinary creature. This recent hatchling is tasting its first foods. Flowers draw its attention in a big way, both because of their color and because of their smell. Turtles have an exquisite sense of smell. And they follow their noses when they have to make certain nutritional decisions. Likewise, their tongues are sophisticated, super-fast chemical analysis labs. When a turtle wants to eat a new plant, it has to take certain precautionary measures. The first one is to take just a tiny bite and wait. Trying a new plant always involves a risk that it might be poisonous and the turtle could die. So the dosage is fundamental. The taste buds on the turtle's tongue send back the test results in just a few seconds. There's no danger in this case. But almost all plants incorporate substances with a bitter taste, like that of poisonous substances. And it isn't always easy to distinguish the plant species that are edible from the ones that aren't. Turtles aren't pollinators. That gift wasn't conceived for them. But they do take advantage of the opportunity. Land turtles eat plants, grasses, or fruit, and rarely eat meat. On the other hand, aquatic turtles are mostly carnivorous. Depending on their size, they can even hunt water birds, although their most common prey are fish. The alligator snapping turtle, Macrochelystomingi, is the largest freshwater species in the world. It lives in the Mississippi River basin, in deep water. Its carapace can reach close to one meter long, and an alligator snapping turtle can weigh more than 100 kilograms. It likes carrion and hunts ducks and small alligators, as well as other turtles whose shells it breaks with its strong beak. But when it's young, it prefers fish. Of course, fish are quite quick, and so it has to catch them by surprise or trick them. The alligator snapping turtle is an extraordinary member of the animal kingdom. It fishes with allure. When it's hungry, it opens its mouth as wide as possible and starts to wiggle a strange appendage at the back of its mouth. The trap is a modified part of its tongue that has its own muscles and that imitates perfectly the movement and appearance of a mosquito larva. It really looks like a live aquatic larva, the favorite food of many fish. The alligator snapping turtle is very patient. It knows how to wait, and it can spend days in the same position, without stopping the show, just in case someone happens to be watching. This group of cichlids seems to have focused their attention on the turtle's lure. But they're not fools, and they have a better memory than people think. Perhaps they've been attacked this way before. Their instincts warn them that something isn't quite right. That's why they have doubts. But they're hungry. And as they say, hunger gives bad counsel. The alligator snapping turtle's technique is practically perfect. Its whole body mimics its surroundings. Its irregular carapace looks like a piece of wood or a stone. And usually, it's even covered with algae or sand. Its head is covered with bumps and warts that break up its silhouette, making it harder for others to recognize it. Its open mouth is a fearsome trap that can clamp down in just hundreds of a second. But to use all these tools together at the same time, it needs a lot of experience. This turtle has already learned that it's pointless to try to chase its prey. It has to stalk them and wait for the right moment. Nobody knows exactly how long the alligator snapping turtle can live, although some have reached ages of over 150 years. Turtles are surprising creatures, but we know very little about them. And some things we have simply made up. We humans tend to attribute certain traits, certain labels, to different types of animals, depending on whether we like them or not, or whether we are afraid of them, or if we can make use of them. But often, we are dead wrong in our judgment of them. We've labeled the big cats as aggressive and ruthless animals that would attack us without a second thought, even if they weren't hungry. Our concept of them can sometimes change if we see, for example, a documentary that describes the female leopard's maternal instincts and shows her playing with her offspring, accompanied all the while by sentimental music. But later, we go back to the preconceptions we have about big cats. It's deceptive. On the other hand, not turtles. Turtles are peace-loving animals, since they don't have fangs, nor sharp claws, nor are they poisonous. Nonetheless, they can be terrifying. This is the largest and strongest tortoise found on a continent, rather than on an island, the African spurred tortoise, Geokelone sulcata. It lives near leopards and lions, but it's not afraid of them. They can't hurt it. It's protected by its shell and the thick scales on its feet. The worst threat to an African spurred tortoise is another African spurred tortoise, that is, when they're both males. Each animal patrols its territory, and thanks to their sense of smell and their droppings, they can stay at an appropriate distance from each other. So if they do run into one another, it's not by chance. The mere presence of another of their kind is a provocation. Even a tortoise can get violent when it's mating season. It's an insult just to be in the other's territory, and there's only one way to respond to that. The normal thing is for the challenger to gauge the strength and determination of his opponent by the force of his blows. And if they're an equal match, the fight will be a fierce one. Their shells can take the hits. But the tortoises aren't trying to break each other's carapaces. They're trying to flip the other over onto his back, so he'll die. This species has a particularly convex shell. Its structure would protect it even from being stepped on by an absent-minded elephant. But that same highly arched structure won't let it turn over now. In this position, its lungs are compressed by the rest of its internal organs, which makes it more difficult to breathe precisely when it needs oxygen most. And today, it's blazing hot in Kenya. The sunlight is shining right on the flat plane of its underside. In just an hour, if it doesn't manage to turn over again, it will die. The victorious male, indifferent to his enemy's suffering, will continue to seek a member of the opposite sex. A shell can be a problem now and then. But most of the time, it's been an essential feature for turtles and tortoises. It's what has allowed them to become what they are. Yes, it's a defensive shield, but it's much more than that. Right now, it's working like a terrific solar panel. Reptiles need to raise the temperature of their blood and organs in order to carry out vital metabolic functions. Taking a sun bath in the morning is even more important for them than having breakfast. In fact, if they didn't take a sun bath, they wouldn't be able to digest their breakfast. The shiny and polished carapace of these tortoises is now quickly capturing the sun's heat, which may also be what saved them when the meteorite that killed off the dinosaurs hit the planet. They certainly know how to get the most out of each ray of sunlight. Taking sun baths is also crucial for their reproduction. Sex is perhaps the most complicated task for a turtle because of how they're built. First of all, their shells make them the least flexible beings in all creation. Copulation requires an exercise in balance and pinpoint accuracy. And, of course, there's no chance of changing postures. And then there's the matter of speed, above all when walking. It probably takes them weeks or even months just to find each other. That's why the mating season for males is so long. They're in the mood practically all year round, which is very unusual among animals because it's exhausting and can be very frustrating. Another complication that limits their ability to find a mate is their visual perspective. Their eyesight is good, but when looking around from so close to the ground, at the level of the plant life, it's not easy to figure out where the rest of your kind are. Many turtles, like this Geocoloni pardalis aethiopiensis, popularly called the leopard tortoise because of the spots on its shell, live in flat places. The absence of hills is an advantage when you have to carry your home with you everywhere you go. But the vast, grassy plains don't offer many raised vantage points from where you can take a look around in search of a date. It seems as if the cards are stacked against sacks for turtles. That's why when a male in the reproductive period crosses paths with a female, he will follow her trail without stopping to rest until he achieves his objective or dies in the attempt. He will literally stick with her as long as necessary. Every once in a while they'll take a break, a short one, just two or three minutes. But as soon as the female has caught her breath, they start dancing the conga again. It's a very serious game for the females. Swept up by his desires, he'll try several times to block her path. He walks around her and stops right in front of her, trying to kindle a change in her attitude. Although, for the moment, she's giving him the cold shoulder. He's been pursuing her for several hours, but it's still not the right time. The male had a really hard time finding her. He was guided by his sense of smell, but luck also played a part, so he's not going to give up. The problem is that the female isn't biologically ready to be impregnated yet. But the male's insistence will provoke her ovulation. If he keeps insisting, day and night. Six days later, several kilometers away from where they first met up, the couple has synchronized their watches, and she finally acts receptive. The enormous biological complications involved in impregnating female turtles is compensated by their ability to store the male's spermatozoa in their reproductive system and ration them out for years. Apart from man, few predators attack turtles or tortoises. Most animals are aware of how pointless it would be to try to break through the formidable defensive structure of these armored reptiles. And so they don't waste their time. But this raccoon is young and inexperienced, and also very hungry and extraordinarily curious. He's looking under the stones in the stream for anything that will calm his grumbling stomach. A crawfish, even though its shell is quite hard, doesn't present a problem. But it's small, and he needs more food. The fang, strength, and intelligence of a raccoon are powerful weapons, and lots of little turtles die to satisfy his hunger. But this is a unique species that has evolved to thwart even this skillful predator. It's a striped mud turtle, Kynosternon bauri, which can close itself up almost hermetically. Its plastron, or the underside of its shell, has a semi-elastic joint that folds up such that not even its feet or tail or anything is left exposed. Its defenses are impregnable. The only option would be to eat it whole. And that's not so easy. These hatchlings have been buried for several months. They're Spanish pond turtles from the Mediterranean region in central Spain. They broke out of their eggs during the warm summer, but they were forced to wait through the autumn and then the winter. At first, the soil was dry and hard from the heat. And then the cold weather arrived. It was impossible to come out. Now it's spring. The temperatures are mild. The soil is softened thanks to the rain. And now's their chance. The moment to really be born. They break through only three or four centimeters of earth toward the light. Their eyes see a warm day. Their instincts immediately orient them all in the same direction. They're looking for water. Fresh water. Because outside of it, they're easy prey for anybody. And they aren't born en masse like their saltwater relatives. Five and six. They're all here. The water is still cold. But soon it will be full of insect larvae. And maybe even a dead fish or two that they can polish off. For now, they have enough with the reserves from the egg to hold out for a week or two. There's no urgent need to eat yet. They should spend their time inspecting the area and looking for hiding places. With a little luck, half of them will reach adulthood. That's a good percentage. Submersion has always been an effective defensive tactic to escape from the hunters that walk on dry land. That's probably how aquatic turtles began their evolutionary journey towards living in the water. The reptiles descend from fish. One day, they left the water to colonize the forests and deserts. But now, the whole crocodilian order and half of the turtles have returned to their ancestral habitat. To do so, they've had to acquire certain adaptations and morphological modifications, like webbed feet and flatter shells that make it easier to swim. They've even learned to breathe intermittently. They can stay underwater for close to an hour without coming to the surface, much longer than any whale. The turtles that live at those latitudes that have alternating warm and cold seasons are even able to hibernate or estivate for months, getting the oxygen they need directly from the water through their supervascularized cloaca, which is almost like the gills of a fish. For eight species of turtles, the sea is their home. About 150 million years ago, they began to colonize the oceans, and they also adapted perfectly to salt water, and to eating algae, and jellyfish, and corals. And so the plodding turtles became the planet's greatest marine voyagers. They're cyclical migratory species, and each year, they travel around the world. The turtles have had enough time to change and adapt to different ecosystems and ways of living. They were originally land animals, but some have evolved to live in freshwater habitats, and others in the sea. Nevertheless, their basic design hasn't changed in the last 300 million years. It's a rare evolutionary feat. That's a long time on the planet. We human beings are still a young species, one of the youngest. Our family is only about three million years old at most, and as a species, we were practically born yesterday. We've lived barely one thousandth of the time that they have. In our legends, turtles are wise and outstanding counselors. We've sensed, unconsciously of course, that the wrinkles on their faces are a sign of ecological wisdom. But they just might be able to teach us a lot about what we should do if we want to continue to live alongside them for a long time in the race of life.