Aldabrachelys gigantea hololissa
Giant tortoises are among the longest-lived animals on the planet. 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 life span of 255 years (birth year 1750). Today, Jonathan, a -year-old, Saint Helena-dwelling Seychelles giant tortoise, is thought to be the oldest living terrestrial animal on Earth since the 2006 death of Harriet; a 176 year old Galapagos giant tortoise who lived at Australia Zoo. Coming in second to Jonathan is Esmeralda, at years old. Esmeralda is an Aldabra giant tortoise that lives in the Galapagos Islands.
Galápagos tortoise
Though the "Beagle" departed from the Galápagos with over 30 adult tortoises on deck, these were not for scientific study, but a source of fresh meat for the Pacific crossing. Their shells and bones were thrown overboard, leaving no remains with which to test any hypotheses. It has been suggested that this oversight was made because Darwin only reported seeing tortoises on San Cristóbal ("C. chathamensis") and Santiago ("C. darwini"), both of which have an intermediate type of shell shape and are not particularly morphologically distinct from each other. Though he did visit Floreana, the "C. nigra" species found there was already nearly extinct and he was unlikely to have seen any mature animals.
However, Darwin did have four live juvenile specimens to compare from different islands. These were pet tortoises taken by himself (from San Salvador), his captain FitzRoy (two from Española) and his servant Syms Covington (from Floreana). Unfortunately, they could not help to determine whether each island had its own variety because the specimens were not mature enough to exhibit morphological differences. Although the British Museum had a few specimens, their provenance within the Galápagos was unknown. However, conversations with the naturalist Gabriel Bibron, who had seen the mature tortoises of the Paris Natural History Museum confirmed to Darwin that distinct varieties occurred.