 Sexual maturity is reached at around 20 – 25 years in captivity , possibly 40 years in the wild . Life expectancy in the wild is thought to be over 100 years , making it one of the longest @-@ lived species in the animal kingdom . Harriet , a specimen kept in Australia Zoo , was the oldest known Galápagos tortoise , having reached an estimated age of more than 170 years before her death in 2006 . Chambers notes that Harriet was probably 169 years old in 2004 , although media outlets claimed the greater age of 175 at death based on a less reliable timeline . 
