 In the 17th century , pirates started to use the Galápagos Islands as a base for resupply , restocking on food and water , and repairing vessels before attacking Spanish colonies on the South American mainland . However , the Galápagos tortoises did not struggle for survival at this point because the islands were distant from busy shipping routes and harboured few valuable natural resources . As such , they remained unclaimed by any nation , uninhabited and uncharted . In comparison , the tortoises of the islands in the Indian Ocean were already facing extinction by the late 17th century . Between the 1790s and the 1860s , whaling ships and fur sealers systematically collected tortoises in far greater numbers than the buccaneers preceding them . Some were used for food and many more were killed for high @-@ grade " turtle oil " from the late 19th century onward for lucrative sale to continental Ecuador . A total of over 13 @,@ 000 tortoises is recorded in the logs of whaling ships between 1831 and 1868 , and an estimated 100 @,@ 000 were taken before 1830 . Since it was easiest to collect tortoises around coastal zones , females were most vulnerable to depletion during the nesting season . The collection by whalers came to a halt eventually through a combination of the scarcity of tortoises that they had created and the competition from crude oil as a cheaper energy source . 
