Madagascar is the fourth largest island in the world after Greenland, New Guinea and Borneo. It is approximately 1000 miles long and its climate reflects its position, lying almost totally within the tropics.
The Birth of Madagascar
Millions of years ago Madagascar was attached to Africa as part of a huge super-continent in the southern hemisphere known as Gondwanaland. Around 150 million years ago (MYA) Madagascar began to break away and started to drift out into the Indian Ocean. At this time reptiles dominated life on earth with the rise of the dinosaur but things were changing. Around 100 MYA, during the early cretaceous period, the climate became warmer and rising sea levels permanently isolated Madagascar from mainland Africa by a 250 mile stretch of shark infested ocean.
The Rise of the Mammals
Meanwhile the first placental mammals began to appear at around 110 MYA and the ancestors to our modern mammals appeared at around 90 MYA. These mammals would not have been present on Madagascar before it was isolated and therefore must have travelled to the island somehow.
Swimming would have been impossible due to strong currents and hungry sharks. Flying is the easiest method and many species of bat flew or were blown across. It is thought that fallen logs and vegetation formed matted rafts which small animals may have become stranded on and then floated across to the island. Obviously the large mammals we commonly associate with Africa such as elephants, lions, zebra, gazelles and giraffe would have been to big to float. Most of Madagascar’s mammals are descended from small ancestral species and only 5 non-flying groups of mammals exist on the island.
Endemic Species of Madagascar
Due to this prolonged isolation the natural history of Madagascar is truly amazing with at least 75% of its flora and fauna found nowhere else on earth. We call these endemic species. Out of its 250 reptiles over 200 are found only on the Island including two thirds of the world’s chameleons. Similarly, almost all of its 133 species of frogs are endemic.
Fossil remains of lemurs have been found in North America as well as Europe indicating that they were once widespread both in the northern and southern hemispheres. They were driven into extinction in all areas other than Madagascar as they could not compete with the smarter monkeys and apes which evolved later.
As these larger primates were never able to make it across the Mozambique Channel the lemurs were able to gradually 'radiate' out into many different species. About 40 to 45 species existed 2000 years ago. Archaeoindris was the largest and is believed to have weighed around 150kg and would therefore have been the size of today's adult male gorilla. One third of lemur species are now extinct with at least another ten classified as 'Critically Endangered'. At the other end of the scale new species are still being discovered or rediscovered including the tiny pygmy mouse lemur Microcebus myoxinus which weighs in at the grand total of around 30g.
Up until 2000 years ago Madagascar must have been a haven for its wildlife. Then the inevitable happened - Homo sapiens arrived and the lemur's lives were about to change forever. The only large predator before then had been a member of the civet family, known as the fossa. Quite surprisingly these early colonists did not come over from Africa, as one might have imagined, but from Indonesia and Malaysia. As they settled they started clearing the forests to create farmland, as a result 85% of Madagascar's forests have now disappeared. Once the protective layer of vegetation has been destroyed erosion occurs quickly as tropical rainstorms, gales and cyclones wash away the exposed topsoil. As a result Madagascar is sometimes referred to as the Big Red Island.
Viewed from space the red, laterite topsoil dominates the landscape and, where the rivers reach the sea it is said to look as if the island is bleeding away. This destruction of their habitat constitutes the greatest threat of all to the lemurs but in some areas hunting is still being practised. Although the Government is now committed to wildlife conservation, in a country as poor as Madagascar the difficulties encountered in ensuring that lemurs are protected rather than killed must be huge. Furthermore, the population is growing rapidly and it is envisaged that in 25 years the population will have doubled.