The rarest animal in the world is no more. Lonesome George, the last of the Pinta Island tortoises, was found dead on Sunday. But a small hope remains for his subspecies, as its genes have survived. “He was an iconic animal for the Galápagos,” says Robert Silbermann, chief executive of the Galapagos Conservation Trust. “It’s devastating to me,” says Gisella Caccone of Yale University in New Haven, Connecticut, who has studied Galápagos giant tortoises for 20 years. “You develop a special bond.” According to the Galápagos National Park, an autopsy will try to determine why George died. He is thought to have been about 100 years old, but Galápagos giant tortoises can live twice that long. “I thought we had more time,” Caccone says. About 14 subspecies of Galápagos giant tortoise (Chelonoidis nigra) once lived on the islands. The differences between them were one of the inspirations for Charles Darwin’s theory of evolution. With the loss of Lonesome George, four of those subspecies have now died out. Thanks to a major conservation programme, the overall population of Galápagos giant tortoises has swelled to around 20,000, from a low in the 1970s of a few thousand. The Hood Island subspecies has recovered from a low of 15 to more than 1200. Nevertheless, the species is still classed as “Vulnerable” by the International Union for Conservation of Nature.
Lonesome George’s subspecies lived on Pinta Island until humans introduced goats that devastated the vegetation and deprived them of food. George was found living alone in 1972 and taken into captivity for his own safety. Conservationists tried and failed to find a female of his subspecies, and attempts to mate him with females of other subspecies didn’t work out. Lonesome George was the last purebred Pinta Island tortoise. A tortoise from Prague Zoo was claimed to be a Pinta Island tortoise, but genetic tests showed otherwise (Animal Conservation, DOI: 10.1111/j.1469-1795.2007.00113.x). But many of the subspecies’ genes live on. Tortoises living around Wolf Volcano on the Galápagos island of Isabela combine the genes from several subspecies. The interbreeding was caused by whalers and pirates, who dumped tortoises on Isabela. These hybrid tortoises preserve genes from several subspecies thought to be extinct, including Pinta Island tortoises. Following that discovery, Caccone led an expedition to the area and collected 1667 DNA samples from the tortoises. Her team is now combing through them, looking for more animals that carry Pinta DNA. The hope was to breed these animals with Lonesome George, but that cannot happen now. However, if there are enough animals of Pinta descent, it should be possible to breed the species back into existence. “By doing selective breeding, you can bring back some of the genetic makeup,” Caccone says.
July 10, 2012
Original web page at New Scientist