• The tortoises comprise the turtle family Testudinidae
  consisting of thirty-nine living species in ten genera.
• Today, tortoises are found in Asia, Europe, Africa,
  oceanic islands and the Americas.
• Included among these are two gigantic forms, the
  well-known Galapagos tortoise (Geochelone elephantopus)
  of the Galapagos Islands in the Pacific Ocean and the
  Aldabran tortoise (G. gigantea) of the Seychelles Island
  in the Indian Ocean.
• Given the long evolutionary history of tortoises
  in North America and the dynamic environment of the last
  thirty million years, it is indeed remarkable that the
  form of the four living North American tortoises has
  changed so little from their ancestors.
• One of these, the desert tortoise, (Gopherus agassizii
  Cooper) is found throughout much of the Sonoran Desert
  region and is therefore of special interest to people
  living in the American Southwest.
• Tortoises may be distinguished
  from other turtle families by the following characteristics:
• The hind legs are cylindrical and elephantine in
  shape: the feet are short, broad and club-shaped.
• In some genera, the forelimbs are flattened and
  adapted for digging and burrowing and the toes are not
  webbed.
• The carapace (upper shell) is usually high and domed
  with the ribs modified in alternating triangular wedges.
• All are terrestrial and basically herbivorous, although
  they may occasionally eat invertebrates and carrion.

ABOUT THE GIANT TORTOISES

• Giant tortoises occur only in Galapagos and on
  Aldabra a toll in the Indian Ocean.
• Weighing up to 270 kilograms, these huge, slow-moving
  reptiles have few natural enemies, but are threatned
  by humans and the animals they introduced.
• Giant tortoises reach maturity at 20 to 30 years.
• They mate during the rainy season, usually between
  January and June.
• Between June and December, the females migrate to
  the arid zones to nest.
• Between 2 and 20 eggs are laid, each about the size
  of a tennis ball. After covering the nest, the female
  returns to the highlands, leaving the eggs to incubate
  for the next 4 to 8 months.
• Nest temperature determines the sex of the hatchlings,
  with lower temperatures producing more males.
• The young tortoises hatch between November and
  April, taking a month to dig their way out from the nest.
• The hatchlings weigh less than 1/1000th of what they
  will weigh as an adult.
• Hawks are probably the only native predator of young
  tortoises. If they can survive the difficult first few
  years of life, they can live for over one hundred and
  fifty years.
• From island to island, giant tortoises vary in size
  and the shape of their shells.
• The smaller saddle-backs, with their long necks and
  limbs and a carapace raised in front, are well adapted
  to the environment on lower, drier islands.
• Dome-shaped tortoises are typical of higher, lusher
  islands, where they feed on grasses, other low-growing
  plants and fallen fruit.