Ancient Frogs and New Castaways _ Land of Gremlins 102.

Imagine a mysterious land of unexplored caves inhabited by crocodiles, sunken forests surrounded by lacerating spikes, where unique creatures tread a dangerous path in extreme conditions. With one eye on the past, another on the future. Living in a land of upside down trees, spiny forests and impenetrable jungle. This isn't a fantasy world but a curious wonderland where nature has run wild. Isolated 400 kilometers off the east coast of Africa is the tropical island paradise of Madagascar. It's the planet's fourth largest island. It boasts an astonishing variety of landscapes from lush rainforests to semi-deserts. Madagascar is also the world's oldest island with its origin in the Jurassic. Its story began 180 million years ago. At that time there was one supercontinent known as Gondwana. But powerful tectonic forces were at work and over an unimaginable amount of time this landmass split into the continents as we know them today. Madagascar was born roughly 88 million years ago. Cut off from the rest of the world for millennia, over 90 percent of the island's animal and plant species are found nowhere else on earth. Ancient Jurassic plants from Gondwana were the first life forms on the island. Isolated these evolved into unique modern species including iconic giants such as the island's magnificent baobabs. Six of the world's eight baobab species occur only on Madagascar. Island life created unique creatures too. Some ancient lineages such as frogs and reptiles were early passengers on the island arc and have adapted and changed in isolation. Incredibly others arrived later as castaways washed up by chance on its shores. Remarkable survivors of a tough ocean crossing from Africa, probably on mats of floating vegetation, these pioneers discovered an island with diverse habitats which they made their own. Today there are over 100 species of lemur that all originated from one such event. Cut off from the rest of the world, Madagascar is the planet's ultimate biological laboratory where being different is a way of life. The island's weather is influenced by a rugged spine of ancient mountains running north to south. These divide the island rising to almost 10,000 feet in places. Created by volcanic activity following the breakup of Gondwana there are no active volcanoes today. However the mountains left behind have an effect on the surroundings almost as dramatic. They create rain. The eastern side of Madagascar is exposed to trade winds laden with water vapor that blow in from the Indian Ocean. Forced to rise over the mountains this moist air cools condensing into raindrops. Heavy rains fall for 240 days of the year or more. The mountains effectively steal water from the rest of the island. As a result Madagascar has a range of climatic regions from warm wet rainforests in the east to cool highlands along the mountainous central spine, dry deciduous forests on the western coastal plain and parched semi-deserts in the south. Each region is home to life forms that have adapted to survive in challenging conditions. Virgin tropical rainforests cloak Madagascar's eastern region home to more than half the species found on the island. The lifeblood of this vast forest ecosystem is water. Rain here is prolific. More than two and a half meters fall every year creating mighty rivers. Temperatures rarely drop below 25 degrees celsius. Perfect growing conditions for tropical trees. Up in the forest canopy leaves form a giant solar powered factory trapping sunlight and converting it to food. The factory's output feeds a vast array of creatures. Between 70 and 90 percent of life in tropical forests exists off the floor up in the trees. Lemurs such as these Milne Edward Sifakas are the most striking treetop residents. While they resemble monkeys they are very different having evolved from a distant ancestor over 65 million years. Unlike monkeys and apes they lack true opposable thumbs or a prehensile tail and have a smaller brain for their body size. Milne Edward Sifakas need to cover large distances in the canopy to find sufficient leaves, seeds and fruit. These agile lemurs are the forest's acrobats. Lemurs are one of the most diverse groups of primates and one in three species live in the island's rainforests. This means competition for food is intense. Red-bellied lemurs avoid this by feeding during both day and night. One of the only lemurs able to do so. This helps them carve out a niche all of their own. The eastern rainforests are also home to a multitude of reptiles found nowhere else such as this amber chameleon one of the world's rarest. Space is at a premium in the precious territories and this male is broadcasting his message in full colour. He's noticed a subordinate male straying into his tree. Puffing himself up and displaying his warning colours to show his displeasure. The resident confronts the intruder. The subordinate turns dark signalling that he's backing down. He doesn't want to risk a fight. Chameleons have fierce teeth and can inflict nasty bites. Their jaws deliver the same bite force as a large dog. So fighting is avoided at all costs. While the canopy is a place of competition and conflict in the understory life is calmer. The trees above protect the forest floor sheltering the inhabitants down below from wind and intense sunlight. Over 95% of light is absorbed in the canopy meaning that little or no primary growth occurs on the forest floor itself. Most organisms here are recyclers reliant on the fallen debris from above. Even giant fallen trees are slowly broken down and recycled by organisms such as these bract fungi. Nothing goes to waste. The forest floor is a unique microcosm crawling with creatures. It's the last place you'd expect to find chameleons. They are specifically adapted to life in the branches and don't usually exist at ground level. Bruchesia chameleons are some of the world's smallest. No bigger than the width of a human thumb. This tiny creature has a trick to help it overcome obstacles. It uses its tail as a walking stick to negotiate its challenging world. More than 300 frog species occur in Madagascar and the rainforests are hotbeds of diversity. None are more striking than the mantellas whose bright colors warn predators that they are poisonous. Mantellas do not produce their own toxins. Their poisonous skin is derived from a diet of ants and other small invertebrates. They are some of the most toxic animals on the planet. It's not only animals that use poison to prevent being eaten in the rainforest. Plants do it too. Some bamboo species contain toxic cyanide to avoid being eaten. Three different species of bamboo lemurs live in the rainforest and each of these is uniquely adapted to forage on slightly different parts of this giant grass. To avoid competition, golden bamboo lemurs have adapted to eat toxic bamboo shoots despite the fact that they're laced with cyanide. Bamboo shoots comprise nearly 90 percent of its diet and they eat as much as half a kilogram in a day, 12 times the lethal dose for an animal its size. Enough even to kill a human. How this golden bamboo lemur is able to tolerate these levels of toxic cyanide is unknown, but being able to do so allows it to thrive amongst its competitors in these crowded forests. Madagascar's eastern rainforests are one of its most diverse habitats. A biological hothouse powered by the sun and fed by rain. This is in stark contrast to other parts of the island. Its mountainous backbone blocks moisture-laden clouds, creating a rain shadow across western and southern regions. It's the dry season in the forests of Kirindi. The trees have shed their leaves to help them conserve water. These deciduous forests are less diverse than the rainforests to the east, but they contain a unique variety of lemurs all of their own. One of the most elegant lemurs on Madagascar. Like its rainforest cousin, it's part of a family of large, athletic lemurs. Leaping is a vital survival skill, not only to travel and find food, but also to keep one step ahead of danger. Predators patrol these dry forests. A hunter specifically evolved to hunt lemurs, which comprise more than half of his diet. The fossa is Madagascar's apex predator. While he looks like a cat, he's more closely related to the mongooses. His retractable claws and reversible ankle joints enable him to climb. But the sifakas are already high in the canopy. This time, they have the advantage. Life in the dry forests of Kirindi must endure six to eight months without rain. Rivers run dry. And yet, in places, there is still water. This small waterhole is fed by an underground spring, and it's attracting a crowd. Grey-headed lovebirds are flocking to the water. So, too, are Madagascar turtle doves. A Madagascar kingfisher is trying its luck. Where life gathers, there's always a watching eye. The harrier hawks hunt for birds, frogs, or even lemurs attracted by the water. This is a favorite hunting area in the dry season. A pair of crested drongos is finding relief at the waterhole. At this time of the year, many forest inhabitants are forced to rest up during the midday heat. Nothing is better adapted to the dry season than baobabs. Madagascar is probably best known for the baobabs that occur across the landscape in the Kirindi region. These giant succulent trees store enough water to survive the dry periods. Their bark has a waxy protective layer to further prevent water loss. Large individuals can reach more than 30 meters high, with trunks 11 meters wide, storing as much as 120,000 liters of water. They are ancient, known as the tree of life for good reason. One of the world's longest living trees, some individuals on Madagascar are more than a thousand years old. Mature trees are often hollow, providing homes for animals, like this family of Madagascar kestrels. They've timed their brood to coincide with the seasonal rains. These will bring a flush of new growth and an explosion of insects. But in this part of Madagascar, weather is unpredictable. Late rains will be devastating for the kestrel family. All life on the dry western coastal plain of Madagascar is governed by the availability of water. Nowhere is this more evident than in the driest part of the island, the spiny desert of the far south of Madagascar. Located in the subtropics, this area remains dry throughout most of the year, receiving less than 400 millimeters of rain annually. It is an ancient landscape, dating from a time when the whole of Madagascar was a dry land. Of the six baobab species on Madagascar, the most unusual looking occurs here, bottle baobabs. This landscape is harsh and unforgiving. Its sandy soils do not retain water, and every plant that lives here is adapted to store water and protect itself against grazers who steal precious leaves. Some defend themselves with spines such as these octopus trees. While they resemble a cactus, they are unrelated. Cactuses form thorns from modified leaves, while the spines of octopus trees grow directly from the branches and stems. The dry, sandy habitats are ideal for reptiles such as this oplerid lizard, distantly related to the iguanids of South America. It's not only the heat that keeps him on the move. A Madagascar ground roller is about, and lizards comprise a large part of her diet. But it's far too hot for hunting. She heads below ground to escape the dry heat of the middle of the day. As the heat intensifies, even the oplerid lizard slows down, languishing in the shade to escape the worst of it. A male succulava weaver is feeling the heat for a different reason. It's breeding season, and he must win over a female by building the perfect nest. She has high standards. This is the fourth nest he's built, but she's still not showing any interest. She's looking for the fittest male to father her chicks, and she chooses on the basis of his nest-building skill. He's not giving up easily. And this time, he's got it right. Perhaps he's the one for her. The female returns with nesting material, proof that she has made up her mind and found her ideal male. While male succulava weavers create the home, it is the female who furnishes it with creature comforts. Domestic bliss. Rain may fall sparingly this far south on the island, but there is a more predictable, if unusual, source of water. Lichen blanketing the southern side of the trees and bushes is a clue to the source of moisture. Along this stretch of Madagascar's coastline, a northward current flows along the shore. This results in the upwelling of deep, cool seawater, which creates fog. As evening falls, the clouds descend, and the fog rolls in, depositing moisture on leaves and branches. This nutrient-rich ocean upwelling also creates bountiful resources for sea life and birds. This is the small island of Nosy V on the southwestern coast of Madagascar. Red-tailed tropic birds nest in loose breeding colonies on the shore. They are monogamous. Both parents assist in incubating the eggs and feeding the growing chicks. After the breeding season, they return to the skies. Eventually, the colony will disperse, individuals wandering the ocean until the next breeding season. The availability of water defines Madagascar's varied landscapes and its wildlife. From its lush eastern rainforests to the dry semi-deserts in the far south, between these two extremes are other unique environments shaped not only by abundance of water or drought, but also by water's power to shape the island's ancient geology. Nowhere is this more obvious than in areas along the mountainous backbone of the island. This is the sandstone landscape of Isalo National Park. It's been heavily eroded by water over millennia. Rain falls on these mountains and the central highlands as warm, moist air is forced upwards. The mountains are a giant sponge, trapping water and releasing it slowly over time, which means water is predictable. And where there is perpetual water, there is life. The rivers carve great canyons across the landscape, which was formed when Madagascar was still part of Gondwana. These canyons are vibrant oases teeming with life. High above, on Isalo's exposed sandstone mountains, conditions are very different. Here, rare plants eke out an existence. This harsh landscape is home to a high diversity of succulents, fleshy plants that can store water. These are a throwback to when Madagascar was a much drier environment. The island has a unique population of distinctive species, such as this red euphorbia. It relies on insect pollinators and offers a rich nectar reward. Insects are drawn to the colourful flower, but beauty is often tinged with danger. A lynx spider lies in wait for a feast, but the spider itself is not immune to danger. A parasitic wasp is looking for a place to lay her eggs. Her target is the spider. She's persistent, aiming to paralyse it with her stinger. If she can immobilise the spider, she will carry it back to her nest and lay her eggs inside its body. After hatching, the wasp's carnivorous larvae will devour the spider alive. But she doesn't get the chance. The wasp killers are homing in. Another wasp is caught in the praying mantis's lethal grip, and the parasitic wasp has paid the ultimate price too. The tables have turned, and she has ultimately fallen victim to the spider. Isalo's sandstone mountains have been carved by water over millennia, creating numerous homes for this unique collection of wildlife. North, along Madagascar's mountain chain, are other impressive landscapes, which have been created by the interplay of rock and weather. Ancient granite mountains dating back millions of years. None are more impressive than the giant domes of Anja Mountain, otherwise known as the Three Sisters. Granite is ancient rock, created by cooling bubbles of molten magma deep under the surface. It's so hard, it resists erosion. Eons of rain doing nothing more than smoothing its surface. These mountains are home to the largest population of ring-tailed lemurs on Madagascar. Ring-tails are the most adaptable lemur on the island. They can survive in a variety of extreme habitats. From Madagascar's parched southern deserts, in winter, these 1,400 metre summits are often dusted with snow. The ring-tails here don't seem to notice. They have thicker than usual coats, and have become masters at the art of rock climbing. Ring-tails share their high-altitude home with a few other resilient plants and animals. They thrive here despite the harsh climate and terrain due to the availability of water, which collects in pools on the rocks, and an abundance of food in the forests that grow in the mountain foothills. Anja Mountain's resilient granite domes have stood the test of time and long resisted the erosive power of rainfall. But there is a place in the far north of Madagascar that is more fragile. Long weathered by storms, it's perhaps the island's most remarkable landscape of all. Ankarana is a natural fortress of stone, fortified by razor-sharp spikes known as tsingy. Only drought-adapted plants can survive on the exposed surface. This is one of the last places on the island you'd expect to find a lemur. But crowned lemurs are tough enough to survive here. Their padded hands and feet enable them to tip-toe across the razor-sharp spikes. They cross this formidable landscape daily as they travel between pockets of forest in search of food. This vast limestone massif formed approximately 150 million years ago in an ancient shallow lagoon on the shores of Gondwana. For millennia, billions of shells of marine plankton along with tons of coral reef fragments settled onto the ocean floor. These sediments were compressed over eons and eventually turned into rock. This new rock was then pushed up by tectonic upheavals. The limestone exposed to the elements, revealing its fragile nature. Limestone is easily eroded. Rain wears away the rock surface, shaping it into jagged teeth and carving deep fissures. As the rain disappears into the cracks, it flows deep into the rock, forming subterranean rivers. These have carved the longest cave system in Madagascar and one of the most extensive in Africa. And Karana's foundations have been eroded into a labyrinth of gigantic caverns. Caves decorated by crystals abound. Water full of dissolved limestone has dripped from the ceiling, every drip leaving the tiniest layer of calcium carbonate behind. Roots from plants growing on the Tsingy surface above are encased in limestone as they inveigle their way through crevices looking for water. These caves are home to an unusual collection of subterranean creatures. Bats hang in the ceiling. The holes where they sit have been eroded into the rock over millennia by their slightly acidic bodies. Over half of all Madagascar's bat species make their home in Ankarana. Under their roosting sites, little piles of droppings known as guano feed a host of cave-dwelling animals. Scorpions too rely on the bats above. While they don't eat guano, they actively hunt the insects that do. But more formidable predators inhabit these dark caverns. This is Crocodile Cave, so named for the crocodiles that lurk in its depths. This is one of the only places on earth where Nile crocodiles have adapted to cave life. Why they do so remains a mystery, but it is thought they may retreat here from scorching temperatures and as a safe sanctuary from human hunters. They may also come here seasonally to hunt the cave-dwelling bats, blind fish and eels that live in the subterranean rivers. Perhaps the most impressive cave of all is the majestic Cathedral Cave. A hole in the ceiling allows a beam of light to strike the cave floor. The hole is growing. Slowly, the rock above is eroded until eventually the roof will collapse. These collapsed caves form sunken pockets in the surface of the Tsingy, which gradually fill with organic matter, forming soils where plants can gain a foothold in this hostile environment. Trees become established and grow into isolated, sunken forests. Some are very different, such as trunkless succulents. They piggyback on the trunks of neighboring trees, reaching for the sunlight without investing heavily in their own support system. These unique forests are islands in a sea of rock. Madagascar is a strange, beautiful, unique world, with a staggering array of habitats and special landscapes. Mountain ranges dominate the island's climate and dictate the lives of its rare inhabitants. Steaming jungles are global hotbeds of diversity. Dry, spiny deserts bristle with danger. Everywhere you look, life here is simply distinct, spectacular and unusual, uniquely adapted to the variety of habitats found across this castaway island.