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July 13, 2000

Why has a large percentage of the original population of giant tortoises disappeared from the Galapagos Islands?

Introduced species are the most devastating threat to populations of native plants and animals in the Galapagos Islands. It was in the 1600ęs that the first humans arrived and that introduction of non-native species began. This was a recipe for ecological disaster which began to escalate in the 1800ęs with the arrival of sealers and whalers. These temporary visitors introduced domestic animals such as horses, donkeys, cattle and goats to the islands in order to ensure a stable food supply. Other foreign species such as Black rats, house mice, cats and dogs either escaped from the holds of their ships or wandered away from early settlers.

Tortoises and tortoise eggs were undefended from such competitors and predators. As a consequence many tortoise populations were reduced dramatically, while others were destroyed altogether.

Listen to Roger Payne's Voice from the Sea piece entitled:
How Finches and Tortoises Contributed to the Theory of Evolution
How Finches Explained Tortoises to Darwin
How the Galapagos Islands Saved Giant Tortoises From All But Humans

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