There are two carapace shapes: the dome, and the saddle-backed. Once on the islands, after consecutive similar events happening many times during a long period of time, they started developing adaptations to feeding and walking around the isolated different islands of the archipelago. This allowed them to reproduce and spread around. These tortoises were better prepared for the environment of the Galapagos and this journey than many other animals, having the ability to survive without much food or water. Tortoises most likely walked on these platforms to cross a river, or to feed, or maybe by mistake and then later got carried with the river currents to the ocean and then to the Galapagos in a long journey in which most animals died. How did the giant tortoises arrive and establish in the islands? The theory states that these giant reptiles were transported by massive floating platforms that were built naturally by heavy rains on the amazon that put down and stocked many trees together. Darwin noticed the difference in the shell shapes of the tortoises according to each island, reaching to the conclusion that they all changed from one single ancestor to the different environments of each island, although the saddle backed shape is thought to have evolved independently from the others. All the species were before considered subspecies of Chelonoidis nigra, but today each one are plain species. Their first ancestor is thought to have first arrived in San Cristobal Island. There are about 15 thousand tortoises living in the islands. They have struggled through volcanic eruptions, fires, hunting and introduced species threats. Currently, they live in 7 different islands of the archipelago. There are now only 11 species, 4 less than when Darwin visited the islands. No reliable data exists to tell the age of a tortoise however, fungi found in the carapaces, together with blood tests can help determine an approximate age. The oldest tortoise known on record was 152 years. The giant tortoise is one of the biggest living reptiles, and they have the longest life from all vertebrates, living more than 100 years.

Pinta giant tortoise scientific name