The Galápagos tortoise or Galápagos giant tortoise (Chelonoidis nigra) is the biggest living species of tortoise and the 10th-heaviest living reptile. It weighs over 400 kg (880 lb) and lengths of over 1.8 meters (5.9 ft). These tortoises are capable of living over 100 years in the wild. This makes them the longest-living vertebrates. A captive individual lived at least 170 years.
The tortoise lives in seven of the Galápagos Islands. The island is a volcanic archipelago about 1,000 km (620 mi) west of the Ecuadorian mainland. Spanish explorers, who discovered the islands in the 16th century, named them after the Spanish galápago, meaning tortoise.
Their shell size and shape are different between populations. On islands with humid highlands, the tortoises are larger, with domed shells and short necks. On islands with dry lowlands, the tortoises are smaller, with "saddleback" shells and long necks. Charles Darwin's observations of these differences on the second voyage of the Beagle in 1835, helped him to develop his theory of evolution.
The population of the Galápagos tortoise is getting smaller. There were over 250,000 individuals in the 16th century. In the 1970s, that number got smaller to around 3,000. The decline is believed to be caused by over-exploitation, habitat loss and introduced species to the islands such as rats, goats and pigs. Ten subspecies of the original fifteen survive in the wild. An eleventh subspecies (C. n. abingdoni) had only a single known living individual. It was kept in captivity and nickname Lonesome George until his death in June 2012.
There have been many conservation efforts, beginning in the 20th century. Because of this, thousands of captive-bred juveniles were released onto their home islands. Also as a result, the population grew to 19,000 at the start of the 21st century. However, the species is still classified as "vulnerable" by the International Union for the Conservation of Nature (IUCN).