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. Box turtles are omnivorous. Their eagle eyes and keen sense of smell help them find foods such as snails, insects, berries, fungi, slugs, worms, flowers, fish, frogs, salamanders, various rodents, snakes, birds, and eggs. During their first five to six years of life they are primarily carnivorous. Adults tend to be mostly herbivores, but do not feed on leafy greens. Box turtles are known to feed on animals found dead on roadways victims of being struck by a car or other rolling vehicle. Hatchlings and young turtles need more protein and prefer a carnivorous diet, to which, as they grow, they incorporate more and more plants. A recent study conducted by Davidson College revealed, among other things, that a box turtle can make sounds with its jaws that exceed 75 dB. This sound can be used to scare away predators and even also as some kind of mating call. While it appears that most matings of Terrapene carolina occur in one-on-one encounters, there are occasions when two males will compete for access to the same female. These encounters, which almost never amount to mortal combat, consist of head-butting, shoving, and perhaps attempts to overturn the other.