Tortoise, any of a group of turtles characterized by column-shaped forelimbs with webless toes tightly bound together. Tortoises are terrestrial and are frequently found in dry country.
In the British Isles the term "tortoise" denotes a much larger group. There, all shelled reptiles, except sea turtles, are called "tortoises" or "terrapins." In the United States, however, the term "tortoise" is limited to some 40 species classified in seven genera and making up the family Testudinidae.
Some tortoises are large, attaining weights of 400 and 500 pounds (180–230 kg) or more. Tortoises are adapted for living on land by their club-shaped feet and webless toes. The shell is usually high-domed, and the head can be completely drawn in. They are long-lived, herbivorous, and slow-moving. In the popular imagination, tortoises are symbols of slow movement and longevity; some live to be more than 100 years old.
Fossil records, dating from Eocene times, some 50 million years ago, suggest that tortoises were once abundant even where they are now only feebly represented, especially in North America. This is borne out by their present wide, but sparse, distribution.
Giant Tortoises. Giant tortoises were once common, but today they are found in only two regions — in the Galápagos Islands, 500 to 600 miles (800–960 km) west of Ecuador, and in some islands of the western Indian Ocean. The tortoise populations in these two regions were once great, but they have been decimated by humans so that some forms have vanished and others are nearly extinct. The Galápagos tortoise (Testudo elephantopus) is usually considered to have 10 subspecies — one on each island. Although there were once several species on the Indian Ocean islands, only T. gigantea survives.
African and Madagascan Tortoises. Africa, Madagascar, and a few nearby islands have the greatest variety of tortoises. Three species belonging to two genera (Testudo and Pyxis) occur in Madagascar, and 18 species, classified in four genera (Geniochersus, Homopus, Malacochersus, and Kinixys), are distributed throughout Africa. Three species of Kinixys tortoises are the only turtles having a hinge in the carapace, or upper shell, which allows them to raise the carapace. The shell of the pancake tortoise (Malacochersus) is so flexible that the plastron, or lower shell, moves when the tortoise breathes. This tortoise is somewhat flattened and, if pursued, can hide in a narrow crevice and inflate itself so that it cannot easily be extricated.
North American Tortoises. Three species of gopher tortoises (genus Gopherus) are found across much of the southern United States and into northern Mexico. They are interesting because of their burrowing habits. Their burrows are sometimes as long as 40 feet (12 meters) and as much as 10 feet (3 meters) below the surface. Gopher tortoises are popular as pets.
Other Tortoises. About 12 species (genus Testudo) occur from southern Europe eastward across southern Asia into Indonesia. Three other species (genus Testudo) extend over much of South America east of the Andes and on to Trinidad and the Windward Islands, with one species occurring as far north as Panama.