Pinta Island tortoise

Evolution

The origin and systematic relationships are still unresolved today; they captivated Charles Darwin himself. DNA sequencing results indicate that the three best candidates for the closest living relative of the Galápagos tortoises all come from South America. They are the yellow-footed tortoise (Geochelone denticulata), the red-footed tortoise (Geochelone carbonaria), and the Chaco tortoise (Geochelone chilensis).^{[citation needed]}

Threats and conservation

Several of the surviving subspecies of Galápagos tortoises are endangered. The decline of the population began in the 17th century as a result of visits by buccaneers and whalers. They hunted tortoises as a source of fresh meat, taking about 200,000 tortoises altogether.

In 1958, goats were brought to Pinta Island and began eating much of the vegetation, to the detriment of the natural habitat.^[17][18] A prolonged effort to exterminate the goats was begun. As the goat populations declined, the vegetation recovered. Small trees began regenerating from the stumps left by the goats. Highland shrub subspecies, forest tree seedlings, Opuntia cactus, and other endemic subspecies increased. In 2003, Pinta Island was declared goat-free.^[19]

In addition to conservation efforts such as the elimination of goat populations in the Galápagos, there has been an effort to revive a number of subspecies of Galápagos tortoise through captive breeding. Future efforts may aim to recreate a population genetically similar to the original Pinta Island tortoise by breeding the first-generation hybrids discovered on Wolf Volcano.

Lonesome George

The last known individual of the subspecies was a male named Lonesome George^[20] (Spanish: El Solitario Jorge),^[21] who died on 24 June 2012.^[7][22][23] In his last years, he was known as the rarest creature in the world. George served as a potent symbol for conservation efforts in the Galápagos and internationally.^[24]

George was first seen on the island of Pinta on 1 December 1971 by Hungarian malacologist József Vágvölgyi. Relocated for his safety to the Charles Darwin Research Station on Santa Cruz Island, George was penned with two females of different subspecies. Although the females laid eggs, none hatched. The Pinta tortoise was pronounced functionally extinct.

Over the decades, all attempts at mating Lonesome George were unsuccessful, possibly because his subspecies was not cross-fertile with the other subspecies.

On 24 June 2012, at 8:00 am local time, Director of the Galápagos National Park Edwin Naula announced that Lonesome George had been found dead^[8][25][26] by his caretaker of 40 years, Fausto Llerena.^[27] Naula suspects that the cause of death was heart failure consistent with the end of the natural life of a tortoise.^[28]

Giant tortoises are among the longest-lived vertebrate animals (more than 100 years by some estimates) and have been used as a model for providing insight into longevity.^[28] DNA analysis of the genomes of Lonesome George and the Aldabra giant tortoise Aldabrachelys gigantea led to the detection of lineage-specific variants affecting DNA repair genes that might contribute to our understanding of increased lifespan.^[28]

Possible remaining individuals

In 2006, Peter Pritchard, one of the world's foremost authorities on Galápagos tortoises, suggested that a male tortoise residing in the Prague Zoo might be a Pinta Island tortoise due to his shell structure.^[29][30] Subsequent DNA analysis, however, revealed that it was more likely to be from Pinzón Island, home of the Chelonoidis Niger Duncanensis subspecies.^[2][30][31]

Whalers and pirates in the past used Isabela Island, the central and largest of the Galápagos Islands, as a tortoise dumping ground. Today, the remaining tortoises that live around Wolf Volcano have combined genetic markers from several subspecies.^[32][33]

In May 2007, analysis of genomic microsatellites (DNA sequences) suggested that individuals from a translocated group of C. abingdonii may still exist in the wild on Isabela.^[34] Researchers identified one male tortoise from the Wolf Volcano region that had half its genes in common with George's subspecies. This animal is believed to be a first-generation hybrid between the subspecies of the islands Isabela and Pinta.^[34] This suggests the possibility of a pure Pinta tortoise among the 2,000 tortoises on Isabela.^[35]

The identification of eight individuals of mixed ancestry among only 27 individuals sampled (estimated Volcano Wolf population size 1,000–2,000)… suggests the need to mount an immediate and comprehensive survey… to search for additional individuals of Pinta ancestry.^[34]

A subsequent trip to Isabela by Yale University researchers found 17 first-generation hybrids living at Wolf Volcano.^[9] The researchers planned to return to Isabela in the spring of 2013 to look for surviving Pinta tortoises and to try to collect hybrids in an effort to start a captive selective-breeding program and to hopefully reintroduce Pintas back to their native island.^[9]

In 2020, the Galápagos national park and Galápagos Conservancy announced that they had discovered one young female with a direct line of descent from the Chelonoidis abingdonii subspecies of Pinta island.^[36]