Giant tortoise species thought to be extinct for 150 years lives on

‘We want to restore them to their island of origin'

January 2012: Dozens of giant tortoises of a species believed extinct for 150 years may still be living at a remote location in the Galápagos Islands, a genetic analysis conducted by Yale University researchers reveals. 

REDISCOVERD: This hybrid tortoise had a pure Chelonoidis elephantopus parent. Picture: Yale University

The analysis suggests that direct descendants of at least 38 pure-bred individuals of Chelonoidis elephantopus live on the volcanic slopes of the northern shore of Isabela Island - 200 miles from their ancestral home of Floreana Island, where they disappeared after being hunted by whalers.

‘This is not just an academic exercise,' said Gisella Caccone, senior research scientist in the Department of Ecology and Evolutionary Biology and senior author of the paper. ‘If we can find these individuals, we can restore them to their island of origin. This is important as these animals are keystone species playing a crucial role in maintaining the ecological integrity of the island communities.'

Hunted to extinction by whalers
On his historic voyage to the Galapagos in 1835, Charles Darwin observed that the shells of tortoises living on different islands of the chain had different shapes - one of the observations that inspired his theory of natural selection. For instance, the shells of C. elephantopus on Floreana were saddle-shaped while tortoises on other islands had domed-shaped shells.

On Floreana, however, the tortoises disappeared because of hunting by whalers and workers at a heating oil factory that had been established on the island.

A team of Yale researchers visiting Volcano Wolf on the northern tip of Isabela Island in 2008 took blood samples from more than 1,600 tortoises and compared them to a genetic database of living and extinct tortoise species.

An analysis detected the genetic signatures of C. elephantopus in 84 Volcano Wolf tortoises, meaning one of their parents was a purebred member of the missing species. In 30 cases, breeding had taken place within the past 15 years. Since the lifespan of tortoises can exceed 100 years, there is a high probability that many purebreds are still alive, say researchers.