These tortoises are widespread except on the highveld, Namib desert or succulent karoo. Generally quite timid they will withdraw into their shells if threatened or disturbed. The horny legs then protect the head which is pulled back into the shell. Terrapins (known as freshwater turtles) do not have the ability to draw head and legs back into their shells. The outer shell is a horn covered bony extension of the rib cage. The domed upper shell called the carapace is covered with scales called scutes. To carry the heavy shell the limbs are large and sturdy and adapted for terrestrial life. They are mainly herbivorous. Lay eggs in the summer. The lower part of the shell is referred to as the plastron and is flat in females and concave in males (which helps prevent the male from sliding off the shell of the female when mounting her during mating). These tortoises do not have teeth but have horny jaws with which they chew their food. Tortoises are believed to be the animals which live the longest.