Terrapene carolina
Terrapene coahuila
Terrapene mexicana
Terrapene nelsoni
Terrapene ornata
Terrapene triunguis
Terrapene yucatana
Cistuda Fleming, 1822
Diducla Rafinesque, 1832
Pyxidemys Fitzinger, 1835
Emyoides Gray, 1844
Onychotria Gray, 1849
Pariemys Cope, 1895
Toxaspis Cope, 1895
North American box turtles are turtles of the genus Terrapene. Although box turtles are superficially similar to tortoises in terrestrial habits and overall appearance, they are actually members of the American pond turtle family (Emydidae). The 12 taxa which are distinguished in the genus are distributed over seven species. They are largely characterized by having a domed shell which is hinged at the bottom, allowing the animal to retract its head and legs and close its shell tightly to protect itself from predators.
The genus name Terrapene was coined by Blasius Merrem in 1820 as a genus separate from Emys, describing those species which had a sternum separated into two or three divisions, and which could move these parts independently.[3] He placed in this genus, among others, Terrapene boscii (now accepted to be Kinosternon subrubrum subrubrum) and Terrapene carolina (but under the name Terrapene clausa). Also several Asian box turtles have been formerly classified within the genus Terrapene; e.g., Terrapene bicolor (now Cuora amboinensis couro) and Terrapene culturalia (now Cuora flavomarginata).[1] Currently, six species are classified within the genus and 12 taxa are distinguished:[1]
Once maturity is reached, the chance of death seems not to increase with age. The survivorship curve of box turtles is therefore probably similar to that of other long-living turtles. The average life span of adult box turtles is 50 years, while a significant portion lives over 100 years. The age of a growing box turtle in the wild cannot be accurately estimated by counting the growth rings on the scutes; Their growth is directly affected by the amount of food, types of food, water, illness, and more. Box turtle eggs are flexible, oblong and are (depending on the taxon) on average 2–4 cm long weighing 5-11 g. The normal clutch size is 1-7 eggs. In captivity and in the southern end of their range, box turtles can have more than one clutch per year, while the average clutch size is larger in more northern populations.[6] Delayed fertility has been observed in female turtles during which a box turtle pair will mate and the female will hold onto the male’s sperm within the cloaca for a period of months or even years before fertilizing and laying a clutch of eggs[7]Turtles can defend themselves from predation by hiding, closing their shell and biting. The risk of death is greatest in small animals due to their size and weaker carapace and plastron. While the shell of an adult box turtle is seldom fractured, the box turtle is still vulnerable to surprise attacks and persistent gnawing or pecking. Common predators are mammals like minks, skunks, raccoons, dogs and rodents, but also birds (e.g. crows, ravens) and snakes (e.g. racers, cottonmouths) are known to kill box turtles.[8]
North American box turtles are omnivores with a varied diet, as a box turtle will "basically eat anything it can catch". Invertebrates (amongst others insects, earth worms, millipedes) form the principal component, but the diet also consists for a large part (reports range from 30 to 90%) of vegetation. The diet is amended with fruits (amongst others from cacti, apples and several species of berry) and gastropods (Heliosoma, Succinea).[9] While reports exist that during their first five to six years, box turtles are primarily carnivorous and adults are mostly herbivorous, there is no scientific basis for such a difference.[9]