How did Tortoises get to the Galapagos?

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Offline Don_1

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How did Tortoises get to the Galapagos?
« on: 10/11/2010 15:53:12 »
The Galapagos archipelago is formed of volcanic islands, each of which has arisen from the ocean bed. The oldest modern island being some 5 million years old. The nearest mainland is 600 miles across the ocean.

The nearest living relative to the Galapagos tortoises (Geochelone Nigra) is the south American Chaco Tortoise (Geochelone Chilensis), though they are not direct ancestors. Divergence of the two species is thought to have happened somewhere between 6 - 12 million years ago.

It has been suggested that the Humbolt Current carried mainland tortoises across the ocean to the Galapagos. Though it is true that a tortoise can survive a long time without food or water, a haphazard journey of 600 miles across the ocean seems a bit too much even for these incredibly hardy animals and the cooling effect of the water might have rendered the tortoise unable to survive.

So how did the tortoises (15 species until Man arrived on the islands) get to the islands? Equally, what about the Iguanas and other terrestrial species?

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Offline Geezer

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How did Tortoises get to the Galapagos?
« Reply #1 on: 10/11/2010 19:23:25 »
Maybe they were stowaways on a turtle?
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Offline RD

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How did Tortoises get to the Galapagos?
« Reply #2 on: 10/11/2010 22:22:19 »
Some plants and animals accidentally move to islands on natural rafts of vegetation.

Difficult to envisage a surfing tortoise though,  (I suppose it could eat bits of raft on a long voyage).

Divergence of the two species is thought to have happened somewhere between 6 - 12 million years ago.

Maybe the geography has changed during than period, e.g. continental drift (approx 1" per year), or "stepping stone" islands which no longer exist, so tortie didn't have to swim so far.     
« Last Edit: 10/11/2010 22:35:39 by RD »