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Whalers spread Galapagos tortoises to other islands

Return of the Georgians
[Via Butterflies and Wheels]

Hopeful news for Galápagos tortoises, maybe. First, the New York Times last week:

Originally there were at least eight species of Galápagos tortoise, scientists now believe. (One was discovered only this year.) At least three species are now extinct, including tortoises on Pinta Island. The last one, George, was discovered wandering alone in 1972 and taken into loving custody. His death, in 2012 at more than 100 years old, was a powerful reminder of the havoc visited by humans on delicate ecosystems worldwide over the last two centuries.

Whalers and pirates grabbed them up because they could live in a ship’s hold for up to a year without food or water.

There are two types of Galápagos tortoises: saddlebacked and domed. The sailors much preferred the smaller saddlebacks, which were easier to lug around and said to taste better. They were also easier to find: Domed tortoises live at higher elevations and can weigh 300 pounds. Saddlebacks evolved at lower elevations and feed on drier vegetation.

Saddlebacked tortoises disappeared from Santa Fe Island and Floreana Island, a favorite hangout for sailors posting letters for other ships to carry home. With George’s death, the Pintas were gone, too.

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Whalers dumped tortoises they did not need into waters surrounding different Islands. At Banks Bay, near Wolf Volcano on Isabela Island. the tortoises apparently made it to shore and have interbred with some of the tortoises on the island.

Perhaps 5% of the animals examined had DNA form tortoises thought extinct. And some of them had parents who were pure-bred tortoises who had become extinct on their native islands.

So, it appears that while whalers did much to destroy tortoises, some of their habits actually helped spread the animals to other islands.

Image: Eric Chan