The Galápagos Tortoise complex or Galápagos giant tortoise complex (Chelonoidis niger and related species) is a species of tortoise found on only a few islands in the Galápagos archipelago, over 600 miles off the Pacific coast of Ecuador. Galápagos giant tortoises are the largest tortoises in the world, with some males weighing more than 500 pounds. Today, there are around 11 species of Galápagos giant tortoise, down from 15 before human contact.
Shell size and shape vary 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 contributed to the development of his theory of evolution. The reptiles are also one of the longest-lived of all vertebrates, with a life expectancy of over 100 years. The oldest individual on record lived to be over 170.
Giant tortoises feed mostly on grass, leaves, fruits, and cactus, and can nap for around 15 hours per day. Due to their slow metabolism, they can survive up to a year without eating or drinking.
All surviving species are endangered, and only around 20,000 of the tortoises are left across the Galápagos. In addition to being hunted by pirates, whalers, and merchants throughout the 17th-19th centuries, they face competition from nonnative species like feral pigs, goats, and cattle. Conservation efforts have brought many Galápagos giant tortoise populations back from the brink. However, breeding, habitat protection, and pest control programs must continue in order for their populations to bounce back fully.