Dodos, giant tortoises and other ancient Madagascan beasts were wiped out by the deadly combination of human activity and a MEGADROUGHT 1,000 years ago
- Researchers studied 8,000 years of climate data from rock and soil samples
- They found evidence of repeated megadroughts in the islands over that time
- Megafauna appeared to have survived previous episodes of extended drought
- The one that finally killed them off coincided with the appearance of humans
Giant creatures from Madagascar and the Mascarene Islands were killed by a deadly combination of human activity and a megadrought, a mineral sample study found.
The creatures, including dodos and giant tortoises, survived through millennia of repeated droughts until humans arrived and finally wiped them out.
Both islands suffered a ‘megafauna crash’ between 1500 and 500 years ago that saw significant large animal and bird species go extinct at about the same time.
Researchers from the University of Innsbruck studied climate data and mineral deposits in Madagascar and the Mascarene Islands dating back 8,000 years.
Experts found that it was likely a ‘double whammy’ of heightened human activities in combination with a particularly severe ‘megadrought’ that doomed the creatures.
The creatures, including dodos and giant tortoises, survived through millennia of repeated droughts until humans arrived and finally wiped them out, authors claim
Nearly all of Madagascan megafauna – including the famous Dodo bird, gorilla-sized lemurs, giant tortoises, and the Elephant Bird which stood 9ft tall vanished.
Theories suggested this could have been due to a changing climate, large droughts over long periods of time – or from overhunting by humans when they arrived.
The Mascarene islands, just to the east of Madagascar, are of special interest because they are among the last islands on earth to be colonised by humans.
‘Intriguingly, the islands’ megafauna crashed in just a couple of centuries following human settlement,’ according to the research team.
The large, charismatic animals that were native to the islands managed to survive repeated megadroughts over thousands of years – before humans arrived.
The team say a combination of hunting, deforestation and other human-caused stressors may have contributed significantly to the extinctions.
While both Madagascar and the Mascarene Islands are considered biodiversity ‘hot spots,’ these islands have lost most of their endemic animals.
Lead researcher Hanying Li and colleagues reconstructed millennial-scale climate trends in calcite deposits from the La Vierge cave in Rodrigues, Mascarene islands.
They determined these deposits represent the climatic record of the region more broadly – rather than just for that island.
Using this proxy data, the researchers defined periods of drier and wetter conditions, observing numerous longer, more severe drying trends throughout the late Holocene than the period in which the megafauna died out.
This suggests that the climate, and severity of the megadroughts, had been much worse at various points in the past than when the creatures went extinct.
The researchers rule out climate change as the one and only cause, and instead suggest that the impact of human colonization was a crucial contributor.
Nearly all of Madagascan megafauna – including the famous Dodo bird, gorilla-sized lemurs, giant tortoises, and the Elephant Bird which stood 9ft tall vanished between 1500 and 500 years ago
The most recent of the drying trends in the region commenced around 1500 years ago at a time when the archaeological and proxy records began to show definitive signs of increased human presence on the island.
Ashish Sinha, professor of earth science at California State University, said they can’t say for certain human activity was the ‘last straw that broke the camel’s back’ but the records suggest that it was the case.
This is because the megafauna had shown a resilience to past climate swings, suggesting an additional stressor contributed to their extinction.
‘There are still many pieces missing to fully solve the riddle of megafauna collapse. This study now provides an important multi-millennial climatic context to megafaunal extinction,’ says Ny Rivao Voarintsoa from KU Leuven in Belgium.
The findings have been published in the journal Science Advances.
WHY DID THE DODO GO EXTINCT?
Little is known about the life of the dodo, despite the notoriety that comes with being one of the world’s most famous extinct species in history.
The bird gets its name from the Portuguese word for fool after colonialists mocked its apparent lack of fear of human hunters.
The 3ft (one metre) tall bird was wiped out by visiting sailors and the dogs, cats, pigs and monkeys they brought to the island in the 17th century.
Because the species lived in isolation on Mauritius for millions of years, the bird was fearless, and its inability to fly made it easy prey.
Its last confirmed sighting was in 1662 after Dutch sailors first spotted the species just 64 years earlier in 1598.
As it had evolved without any predators, it survived in bliss for centuries.
The arrival of human settlers to the islands meant that its numbers rapidly diminished as it was eaten by the new species invading its habitat – humans.
Sailors and settlers ravaged the docile bird and it went from a successful animal occupying an environmental niche with no predators to extinct in a single lifetime.
Other birds, such as the kakapo in New Zealand, also evolved to be similarly fearless, plump and sluggish.
As humans spread around the world, they also decimated the population numbers of these birds.
The kakapo is now an endangered species.
The dodo (left) is now extinct after a 17th century assault of hungry sailors destroyed the population of the docile, fearless birds. The kakapo (right) is a similarly flightless, fearless bird that is now struggling to survive and is currently endangered