Story highlights Giant tortoise Lonesome George dies in Galapagos Islands

George was the last surviving member of the Pinta Island subspecies

He was more than 100 years old -- comparatively young for a giant tortoise

The cause of his death is under investigation

Lonesome George, the last surviving Pinta Island giant tortoise, has died at his home in the Galapagos Islands. Scientists believe he was more than 100 years old.

Staff at the Galapagos National Park in Ecuador say George, the only remaining member of his subspecies (Chelonoidis abingdoni), was found dead by his long-term keeper, Fausto Llerena.

In a statement the national park said Llerena had been "unhappily surprised" to discover his charge "stretched out in the direction of his watering hole with no signs of life," on Sunday morning.

A post-mortem examination will be carried out to ascertain the cause of death, as although he was old by human standards, Lonesome George was not considered old for a giant tortoise -- the animals can live to around 200 years of age.

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George became a symbol of the Galapagos Islands after he was found on Pinta Island by biologist Joseph Vagvolgyi in 1971.

His plight as the only known member of his subspecies led to a series of ill-fated attempts to provide him with a mate.

But despite the best efforts of conservationists -- and the presence of two female giant tortoises from a close subspecies sharing his enclosure at the Charles Darwin Research Station on Santa Cruz -- George remained a solitary creature.

His death marks the end of the purebred Pinta Island tortoise, but there is hope that they will survive in some form: at least one first-generation descendant of the subspecies has been found at the Wolf volcano on neighboring Isabela Island.

Genetic testing has been carried out to try to find further hybrids among the population there.

The giant tortoises of the Galapagos helped Charles Darwin formulate his theory of evolution after he visited the islands in the 1830s, on his five year voyage aboard HMS Beagle.

At the time, the super-sized reptiles were common, but the introduction of wild goats, which ate the vegetation that formed their diet, and the hunting habits of passing sailors -- left them on the brink of extinction.