The Common box turtle is a medium-sized North American species of turtle. It gets its common name from the structure of its shell which consists of a high domed carapace (upper shell), and large, hinged plastron (lower shell) which allows the turtle to close the shell, sealing its vulnerable head and limbs safely within an impregnable box. The carapace is brown, often adorned with a variable pattern of orange or yellow lines, spots, bars, or blotches. The plastron is dark brown and maybe uniformly colored, or show darker blotches or smudges. The Common box turtle has a small to the moderately sized head and a distinctive hooked upper jaw. The majority of adult males have red irises, while those of the female are yellowish-brown. Males also differ from females by possessing shorter, stockier, and more curved claws on their hind feet, and longer and thicker tails.
Common box turtles are found in the eastern United States, from Maine and Michigan to eastern Texas and south Florida. They occur in Canada in southern Ontario and in Mexico along the Gulf Coast and in the Yucatán Peninsula. These turtles live in open woodlands, roadsides, road middles, marshy meadows, floodplains, scrub forests, and brushy grasslands.
Common box turtles are mainly terrestrial reptiles that are often seen early in the day, or after rain, when they emerge from the shelter of rotting leaves, logs, or a mammal burrow to forage. In the warmer summer months, they are often seen near the edges of swamps or marshlands, possibly in an effort to stay cool. If Common box turtles do become too hot, (when their body temperature rises to around 32 °C), they smear saliva over their legs and head; as the saliva evaporates it leaves them comfortably cooler. Similarly, they may urinate on their hind limbs to cool the body parts they are unable to cover with saliva. In the northern parts of their range, Common box turtles may enter hibernation in October or November. They burrow into loose soil, sand, vegetable matter, or mud at the bottom of streams and pools, or they may use a mammal burrow and will remain in their chosen shelter until the cold winter has passed. They are social creatures and may even hibernate together.
Common box turtles are polygynandrous (promiscuous), meaning that both the males and females have multiple partners. Courtship usually takes place in spring and begins with a "circling, biting and shoving" phase. These acts are carried out by the male on the female. Remarkably, female Common box turtles can delay implantation for up to four years after mating, and thus do not need to mate each year. In May, June, or July, females normally lay a clutch of 1 to 11 eggs into a flask-shaped nest excavated in a patch of sandy or loamy soil. After 70 to 80 days of incubation, the eggs hatch, and the small hatchlings emerge from the nest in late summer. They are typically highly secretive and are seldom seen. The young become reproductively mature at 5 years of age.
Although Common box turtles have a wide range and were once considered common, many populations are in decline as a result of a number of diverse threats. Agricultural and urban development is destroying their habitat, while human fire management is degrading it. Development brings with it an additional threat in the form of increased infrastructure, as Common box turtles are frequently killed on roads and highways. Collection for the international pet trade may also impact populations in some areas.
There is no overall population estimate available for Common box turtle. However, there is an estimated population of its subspecies Yucatan box turtle which is most likely less than 10,000 individuals. Currently, the Common box turtle is classified as Vulnerable (VU) on the IUCN Red List and its numbers today are decreasing.
Due to their varied diet, Common box turtles help to control various prey populations. They may also aid in seed dispersal around their native range as they consume berries of different plants.