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Fast Facts:

What is the difference between a turtle and a tortoise? Generally speaking, tortoises live on land and do not swim. Many turtles, such as sea turtles, spend almost their entire life in water. Other turtles, such as wood and bog turtles, are semi-aquatic, living in wetland areas. Box turtles live on land, but are still referred to as turtles rather than tortoises.

Aldabra Tortoise

Scientific Name	Geochelone gigantea
Classification	Phylum Chordata, Class Reptilia, Order Chelonia, Family Testudinidae
Status	Aldabra tortoises are classified as "Rare in the wild" by the IUCN
Range	Aldabra tortoises are native to the islands of the Aldabra atoll in the Indian Ocean.
Habitat	Most of the tortoises are found on the south coast of South Island, one of the four islands in the chain.
Diet	Herbivore
Size	150 - 500 lbs; females are usually considerably smaller than the males
Lifespan	Turtles and tortoises may live 50 years or more.
Location
Print Fact Sheet	Aldabra Tortoise

Conservation

Aldabra tortoises are classified as "Rare in the wild" by the IUCN (International Union for the Conservation of Nature), and are still considered "at risk" for extinction because they are found in such a restricted habitat. The wild population of Aldabra tortoises is estimated at 33,000 animals.

Giant tortoises were once found on many of the islands in the Indian Ocean. Today, the Aldabra tortoises of the Aldabra atoll are the only surviving giant tortoises of the Indian Ocean islands. The other species became extinct in the 17th and 18th century, largely due to over-hunting by seafarers who would stop on the islands and kill the tortoises for food. The Aldabra tortoises were spared because the rocky terrain of the Aldabra islands made it too difficult for seafarers to kill the large tortoises and load them onto their boats.

In 1960, the Aldabra tortoises faced potential extinction when the British government made plans to construct an airstrip and human settlement on the islands. However, the island ecosystem was saved when a study conducted by Cambridge University concluded that the Aldabra atoll was one of the richest and least disturbed atolls in the world. In 1982, the atoll was named a World Heritage Site by UNESCO (United Nations Education, Scientific, and Cultural Organization). This designation will help preserve the delicate island ecosystem in its natural state.

Special Features

Tortoises and other reptiles are ectothermic. That means that they are not able to regulate their body temperature in the same way that mammals and birds are. Ectothermic animals aren't able to generate enough body heat to maintain a constant temperature. They maintain a preferred body temperature by moving between warm, sunny spots and cooler, shady areas.

Another group of shelled reptiles, the terrapins, spend part of their time on land. The tortoises' large shells provide protection. Their shells are composed of bony plates covered by a layer of scales, known as scutes. The scutes are made of keratin. The upper shell is called the carapace, and the lower shell the plastron. When danger approaches, the tortoises withdraw into the safety of their shells.

Tortoises do not have teeth. They depend on the tough horny "beak" on the front of their upper jaw to help bite off pieces of food that are usually swallowed whole.

Tortoises, like most reptiles, have a three-chambered heart. Crocodilians are the only reptiles with a four-chambered heart.

To the casual observer, Aldabra tortoises look quite similar to Galapagos tortoises. Galapagos tortoises are an endangered species from the Galapagos Islands, located in the Pacific Ocean off the west coast of Ecuador.

Social Structure & Behavior

Aldabra tortoises are often not able to successfully reproduce until they reach their twenties.

Females lay their eggs in nests dug in sandy soils. The eggs are about the size of tennis balls. The number of eggs laid may be affected by the population density of the area. In an area with many animals, a female may only lay 1 clutch of 4 to 5 eggs every few years. In low-density areas, the females may lay several clutches of 12-14 eggs each year.

Temperature can affect hatching times. Eggs exposed to warmer temperatures require about 110 days to hatch. In colder conditions, eggs may take 250 days to hatch.

Newly hatched tortoises are vulnerable to attack by predators, such as birds and crabs, until their shells begin to harden and they reach a weight of about 15-20 pounds.