(CNN) -- 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.