Aldabra giant tortoise
Large tortoises are among the longest-lived animals. Some individual Aldabra giant tortoises are thought to be over 200 years of age, but this is difficult to verify because they tend to outlive their human observers. Adwaita was reputedly one of four brought by British seamen from the Seychelles Islands as gifts to Robert Clive of the British East India Company in the 18th century, and came to Calcutta Zoo in 1875. At his death in March 2006 at the Kolkata (formerly Calcutta) Zoo in India, Adwaita is reputed to have reached the longest ever measured lifespan of 255 years (birth year 1750). Today, Jonathan, a Seychelles giant tortoise ("A. g. hololissa"), is thought to be the oldest living giant tortoise at the age of years and Esmeralda is second at the age of years, since the death of Harriet at 176, a Galapagos giant tortoise. Esmeralda is an Aldabra giant tortoise.
Giant tortoise
Giant tortoises are characteristic reptiles that are currently found on two groups of tropical islands: the Aldabra Atoll and Fregate Island in Seychelles and the Galapagos Islands in Ecuador (a population at the Mascarene Islands was exterminated by the 1900s). These tortoises can weigh as much as and can grow to be long. Giant tortoises originally made their way to islands from the mainland; for example, the Aldabra Atoll and Mascarenes giant tortoises are related to Madagascar tortoises while the Galapagos giant tortoises are related to Ecuador mainland tortoises. This phenomenon of excessive growth is known as island gigantism or insular gigantism. It occurs when the size of the animals that are isolated on an island increases dramatically in comparison to their mainland relatives. This is due to several factors such as relaxed predation pressure, competitive release, or as an adaptation to increased environmental fluctuations on islands. However, giant tortoises are no longer considered to have been examples of island gigantism, as they originally evolved their massive sizes on the mainland. Giant tortoises were once common across the Cenozoic faunas of Eurasia, Africa and the Americas.