Box turtle is the common name for several species of turtle. It may refer to those of the genus Cuora or Pyxidea, which are the Asian box turtles, or more commonly to species of the genus Terrapene, the North American box turtles. They are largely characterized by having a shell shaped like a dome, which is hinged at the bottom, allowing the animal to close its shell tightly to escape predators. Furthermore, the two genera are very different in habitat, behavior and appearance, and are not even classified in the same family. Even though box turtles became very popular pets, their needs in captivity are complex and the capture of turtles can have serious detrimental effects on the wild population. The box turtle commonly lives over twenty years, with verified cases of lifespans exceeding 40 to 50 years. There have been unverified cases of box turtles living for a hundred years and more.