1 June 1998
At 167 years of age, Harriet, a Giant Galapagos Land Tortoise, is probably the oldest-living captive animal in the world. Her species Geochelone nigra, is the longest-lived of all known animals.
Don Boyer, Associate Curator of Herpetology at the San Diego Zoo says that the life span of Galapagos tortoises is about 150 years. Some scientists estimate that Harriet has a good change of reaching the ripe age of 200.
Weighing up to 600 pounds, these lumbering reptiles are remarkable for their elephant-like feet, necessary to support their incredible weight. The largest of all tortoises, the Galapagos grows from a three-ounce hatchling to an animal the size of a card table. Striking, too, are the animals’ carapaces, or the top part of the shell.
The Galapagos Islands achieved fame, of course, when British naturalist and evolutionary theorist Charles Darwin led an expedition there in 1835. At the time, Harriet was just a kid at about five years old, and it was her fortune to join the expedition on the HMS Beagle. Fate took her away from home, and also might have saved her from becoming some whaler’s dinner. After spending time in London, she made her way to Australia in 1842, where she now resides at the Australia Zoo on Queensland’s Sunshine Coast. The grand dame of the Galapagos will celebrate her 168th birthday in November, a month selected because the tortoises lay their eggs at that time.
Scientists arrived at the educated estimate of Harriet’s age by piecing together historical records and photos that document her travels as well as DNA testing showing that Harriet is at least two generations (140 years) older than the wild giant tortoises inhabiting her birthplace, the Galapagos Island of Santa Cruz. A precise birth date cannot be determined, explains Kelly Zontanos, Education Coordinator of the Australia Zoo.
DNA testing is an important tool in determining the subspecies and pedigrees of other captive giant tortoises, particularly those in zoo breeding programs. Galapagos tortoises are believed to have evolved from a common ancestor, but their evolution occurred in isolation – the reptiles bred in separate groups on nine individual islands. Five of the subspecies are from the island of Isabela, with each group confined to one of the island’s five major volcanoes. Three subspecies are extinct and one, from Pinta Island, has only a single survivor – an 80-year-old male nicknamed ‘Lonesome George’.
Captive breeding is important to the survival of these endangered animals, according to Boyer. Once exploited for food and oil, their native population was reduced from 250,000 to fewer than 20,000. Today feral animals such as pigs, goats and dogs threaten tortoise nests and food sources.
The Charles Darwin Research Station and the Galapagos National Park Service on Santa Cruz Island protect and breed tortoises. The remoteness of certain subspecies in the archipelago has been so problematic that conservationists play matchmaker.
The Espanola Island subspecies had been reduced to only two males and 11 females whom isolation had deprived of a mate. In 1965, 13 were introduced at the research station and within 20 years the group produced more than 200 hatchlings. Now living on Espanola, these youngsters, it’s hoped, will establish a new community of Galapagos tortoises to live long and happy lives.