Endangered Species Handbook

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Madagascar and other Islands

Madagascar

     Imagine an island more than 1,000 miles long in a blue tropical ocean. Forests cover vast areas, interspersed with swamps where crocodiles 8 meters long lie in wait to prey on pygmy hippopotamuses.  Thousands of giant tortoises with shells 4 feet across lumber about.  In the forests and in dryer parts of the island live some of the strangest primates to have ever existed on Earth.  Some 45 species of these lemurs live throughout the island and range in size from the world's smallest primate, weighing about 1 ounce, to a lemur the size of a Gorilla (Tattersall 1993).
 
     Huge white birds plod along forest trails and through savannah grasses.  Many kinds of these birds inhabit the island.  The largest resembles an Ostrich, but is far more massive in build, weighing 1,000 pounds (Feduccia 1996).  It stands 10 feet tall and lays 20-pound eggs, 13 inches long (Feduccia 1996, Greenway 1967).  More than 100 other kinds of tropical birds that exist nowhere else fly in forests and deserts and wade in still marshes.
 
     Primitive hedgehog-like mammals, called tenrecs, scurry in forest underbrush. One type of tenrec lives in cold mountain streams, swimming with webbed feet and flattened tail, while another has spines like a porcupine and stripes down its back like a skunk.  It communicates with its young by vibrating its spines.
 
     Hundreds of kinds of amphibians and reptiles inhabit forests, aquatic environments, savannahs and drylands.  Frogs of every imaginable color and pattern leap in green shadows.  Chameleons, some brilliantly colored, and others shades of mottled brown, creep invisibly about.  The largest, 2 feet long, can capture mice and birds, while the smallest, measuring only 1.5 inches, feeds on insects (Amos 1980).  Tortoises with shells adorned in delicate yellow sunburst patterns inhabit shrub and deserts.
 
     Plants exist in unparalleled variety, a botanical paradise.  Relicts of species long-extinct on mainland areas--tall tree ferns, palms, red-flowered flame trees, massive deciduous and rainforest trees, giant tamarinds and aloes, desert oddities, and baobabs of many sizes--grow in even the driest parts of the island.  Orchids in a rainbow of colors bloom among the deep green rainforests.  Waterfalls abound, cascading down tall cliffs into rivers and lakes.  Along the west coast, a dry deciduous forest stretches the length of the island.  The central highlands are a mosaic of woodland and savannah, while the eastern regions are covered in dense, humid rainforest.  In the extreme south, a desert environment prevails, harboring Didierea, strange cactus-resembling plants that form long, spiny, twisted shafts rising 30 feet into the air.  An impenetrable wilderness of limestone spikes and sharp rocks dominates the far north.  Rare birds and lemurs find refuge in this craggy landscape and feed in oases watered by meandering streams.
 
     Flightlessness, fearlessness, gigantism, dwarfism, and survival of ancient species all occurred in this evolutionary laboratory.  That such a large land mass went uninhabited by humans for so long is truly remarkable.  Nowhere else on the planet has such a large land area remained isolated for such a prolonged period, allowing a flowering of diverse life forms to flourish and adapt to the island's many habitats and terrains in this mild, tropical climate.  Such is the history of the island from Madagascar in 400 A.D., a century before the arrival of the Malagasy people of Asia.  Had humans reached Madagascar earlier, it might not have evolved its diverse, yet vulnerable, fauna and flora. 
 
     How such an extraordinary diversity of animals and plants inhabits Madagascar is tied to its geological history.  Some 160 million years ago, when Africa, Australia, New Zealand and South America were united in the super-continent Gondwana, Madagascar was attached to eastern Africa and what is now peninsular India.  Dinosaurs, giant turtles, crocodiles, primitive mammals, reptilian birds and lizards roamed on this massive land mass.  Gondwana gradually broke apart as a result of movements of tectonic plates covering the Earth's crust.  For many millions of years, India and Madagascar formed a mini-continent.  Then, about 88 million years ago, they split along Madagascar's east coast, and peninsular India moved northward toward Asia (Garbutt 1999, Tyson 2000).  Paleontologists have only recently discovered that Madagascar was home to dinosaurs and other primitive animals quite unlike those found in other parts of the world.  The oldest known species of dinosaur, dating back 227 million years, may be the ancestor of all dinosaurs (Flynn 2000).  One dinosaur had teeth that were clove-shaped (Stenzelt and Thiessen 2000).  Seven species of crocodiles inhabited Madagascar from the Cretaceous period onward, including a pug-nosed vegetarian species (Flynn 2000).  About 65 million years ago, the last dinosaurs died out, concurrent with their extinction throughout the world.  Some native plants and animals survived from the time when Madagascar was part of Gondwana.  Giant tortoises, crocodiles, boas, tenrec ancestors and possibly an early form of elephant birds may have lived on the super-continent, although most ornithologists are certain that the ancestor of the elephant bird flew to the island and became flightless (Feduccia 1996).  Plants of many kinds, virtually unchanged from their ancient forms, grow on the island. 
 
     Immigrant animals arrived during the millennia from many sources.  Because Madagascar separated from India and Gondwana long before the evolution of the prosimians that were the ancestors of the lemurs, these primates must have come from mainland Africa, where their close relatives, bush babies and galagos, survive today.  Some scientists believe they might have traveled over a land connection that existed between Africa and Madagascar at some point (Tyson 2000).  Others dispute that there ever was such a land bridge and maintain that they arrived by sea, perhaps sheltering on large mats of floating vegetation or clinging to uprooted tree trunks that swept down mainland rivers to the sea and washed up on Madagascar's shores.  Few modern mammals of Africa, whether baboons, monkeys, gazelles, antelope or other hoofed mammals, reached Madagascar.  The hippopotamuses must have originated in Africa, but how they came to the island is another mystery.
 
     Over many millennia, a blossoming of evolution occurred in this mild, tropical climate of Gondwandan and immigrant species, radiating into entire new families and creating a flora and fauna of great diversity unlike any in the world.  Birds, bats and insects flew or were blown to the island by wind currents and storms from Africa and Asia.  No large carnivores arrived, however.  The largest mammal predators are relatives of mongooses, primitive viverrids.  Grazing and browsing roles were filled by hippopotamuses, land tortoises, lemurs and elephant birds.


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