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Galapagos Giant Tortoise goes un-extinct

January 9th, 2012

From Green Right Now Reports

A C. elephantopus hybrid turtle.

In a story that gives new meaning to the phrase ‘slow and steady wins the race,’ a giant tortoise long thought extinct appears to be still alive on one of the Galapagos Islands.

Scientists have determined that the tortoise subspecies Chelonoidis elephantopus, thought to have disappeared nearly 150 years ago, may roam the northern reaches of the island of Isabela, several miles from the tortoise’s native island, Floreana.

Using field work and genetics testing, a team led by scientists from the Ecology and Evolutionary Biology Department at Yale University, found dozens of hybrid giant tortoises whose genetic lineage indicates that one parent is a C. elephantopus, also known as a Floreana tortoise.

The tortoises tested were living near Wolf Volcano on Isabela island, and many were quite young, suggesting that their Floreana purebred parent was still around.

The Galapagos Conservancy reports on the finding:


Having previously found a small number of hybrid tortoises on Wolf Volcano, scientists returned in December 2008 to obtain blood samples from a total of 1669 individuals, approximately 20% of the estimated current tortoise population.

Results reported this week indicate that 84 tortoises were found whose DNA show that they resulted from hybridization events involving a pure Floreana tortoise as one of their immediate parents. Thirty of the 84 tortoises were determined to be less than 15 years old – indicating that the likelihood of pure Floreana tortoises still roaming the slopes of Wolf Volcano is quite high. Historical records indicate that tortoises were often moved between islands by whalers and other visitors to Galapagos in the 18th and 19th centuries, and many ended up on Wolf Volcano. These historical records provide an explanation for the unusually wide range of tortoise types found there — a population mix that would not be expected to occur naturally.

The report is a rare bit of good news in an otherwise cloudy outlook for turtles and tortoises worldwide. In 2011, the International Union for Conservation of Nature (IUCN) warned that half of the world’s turtles and tortoises face a risky future.

“Turtles are in serious trouble. They are some of the world’s most endangered vertebrates, more than mammals, birds, or even highly endangered amphibians. Half of their species are threatened with extinction,” said Dr. Anders Rhodin, co-editor of a report for the IUCN’s Tortoise and Freshwater Turtle Specialist Group . “They’re being unsustainably collected from the wild for food, perceived medicinal beliefs and pets while their habitats are being polluted, degraded and destroyed every day.”

Dr. Linda Cayot, who studies the Galapagos tortoises for the Galapagos Conservancy, explains where the C. Elephantopus fits among the various subspecies of tortoises on the islands. Cayot:

The taxonomy of tortoises has changed several times since I began studying them in 1981.  There are 14 different species/subspecies.  When I first started working on tortoises, they were considered subspecies of a single species.  More and more they are considered separate species and the genetics group now refers to them as such.  Each species is separated from the others – either by being on a separate island or the five species on Isabela live on 5 volcanoes with extensive lava fields between them and the populations don’t intermix.    There are two major forms – domed (the ancestral and larger form) and saddle-backed (smaller and found on the more arid islands).  Chelinoidis elephantopus is sort of in the middle – a bit larger than the saddlebacks but still with a raised front section of the carapace.

Next, scientists are planning a return trip to Wolf Volcano for later in 2012, in hopes of finding pure Floreana tortoises.

“Depending on the number found, it is likely that they will then be put into captivity and a breeding program started, rather than releasing them into the wilds of Floreana,” Dr. Cayot said. “When a population is so low – you need to jumpstart it rather than just put the tortoises back into the wild. In the wild, the majority of hatchlings die each year. By breeding them in captivity, this mortality can be kept below 5%. This will also happen even if they don’t find pure tortoises – and through selective breeding they should be able to get closer to Floreana tortoises – to eventually be released on Floreana.”



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