Reptiles of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

NC Records
Emydidae Members:
Terrapene carolina - Eastern Box Turtle

Photo: S. Hall

Photo: J. Mickey

Taxonomy

Class: Reptilia

Order: Testudines

Family: Emydidae

Subfamily: Emydinae


Taxonomic Comments: Terrapene is a North American endemic genus, with species ranging from Mexico to southern Ontario (see Dodd, 2001). Along with Clemmys, Glypemys, and Emys, Terrapene is included within subfamily Emydinae of the Emydidae, a group confirmed by DNA analysis to be closely related (see Feldman and Parham, 2002; Spinks et al., 2009). Traditionally, four species were recognized within Terrapene (Dodd, 2001), with two additional species recently proposed as splits from Terrapene carolina (Martin et al. 2013; but see Fritz and Havas, 2014).
Species Comments: Only a single species in this genus, Terrapene carolina, occurs along the Atlantic seaboard, with the nominate subspecies the only one found in North Carolina.

Identification

Description: Box Turtles are among our most widely recognized reptiles, with their highly domed carapace and hinged, tightly closing plastron easily identifying at least the adults of this species (hatchlings have a shell morphology similar to other members of the Emydidae). The carapace is typically marked with spots, blotches, and rays of yellow or orange on a dark background; this pattern serves as very effective camouflage when the turtle is resting on hardwood leaf litter, their normal substrate. The head and limbs may also be similarly colored and the eyes -- particularly in the males -- may be a bright strawberry red or orange.

Morphological Features: Box Turtles are moderately sized, with males averaging larger than females. The largest specimen measured by Palmer and Braswell (1995) had a carapace length (straight-line) of 152 mm (5.98 in). This species is sexually dimorphic, with males having a concave plastron (generally flat in females), strongly curved claws on the hind feet (long and slender in the females), and a longer, thicker tail. The males are also generally more brightly colored, particularly on the head and forelegs, and have a brighter orange or red iris (usually brown or dark red in the females). Hatchlings and juveniles up to about the age of three have a relatively flat carapace and lack a functioning hinge on the plastron. They are generally brownish but have a mid-dorsal keel on their carapace that has light colored bumps.

Technical Reference: Palmer and Braswell (1995); Dodd (2001); Ernst and Lovich (2009)

Field Guide Descriptions: Beane et al. (2010); Powell et al. (2016)

Online Photos: iNaturalist; Herpmapper Google iNaturalist GBIF

Observation Methods: Due to their excellent camouflage and ability to detect potential predators (or humans) at some distance and remain immobile for long periods, Box Turtles are commonly overlooked by humans walking through their habitats, frequently stepping right over them unawares (S. Hall, pers. obs.). The use of dogs that are trained to locate Box Turtles by scent -- pioneered by Charles and Elizabeth Schwartz in the 1960s (Schwartz and Schwartz, 1974)-- provides a much more effective way to find them in the field.

Distribution in North Carolina

Distribution Comments: Box Turtles are found throughout the state, occurring in every county and ranging from the barrier islands to the Mountains. Although usually found below 4,000', Box Turtles have occasionally been found above 6,000' at both Mt. Mitchell (Palmer and Braswell, 1995) and Clingman's Dome in the Great Smokies (Tilley and Hughey, 2010).
Distribution Reference: Linnaeus gave the type locality for Testudo carolina as "Carolina" and John Lawson described a "Land Terebin" -- most likely Terrapene carolina -- during his travels through the Carolinas in 1700-1701 (Hairr, 2011)
County Map: Clicking on a county returns the records for the species in that county.

Key Habitat Requirements

Habitat: Eastern Box Turtles inhabit a wide range of hardwood forests, from fairly dry ridgetops to floodplains. Other habitats are used opportunistically, including fields, shrublands, and pine-dominated stands, but usually where they are located adjacent to stands of hardwoods. Frequently burned habitats, including Longleaf Pine savannas, flatwoods, and sand ridges, do not appear to be routinely used, although they may inhabit streamhead swamps and bottomland forests -- all much less frequently burned -- that border or extend into those habitats (S. Hall, pers. obs.).

Environmental and Physiological Tolerances: Box Turtles are tolerant of fairly cold winter temperatures and can survive at least short periods of freezing (see Dodd, 2001, for a review). Winter kills, however, have been observed but appear to be rare events, occurring under only very extreme combinations of weather factors. During their active portion of the year, Box Turtles regulate their body temperature primarily by behavioral means: basking in the sun in order to warm up and retreating to cool, moist microclimates to avoid potentially lethal high temperatures. Dodd (2001) notes that Box Turtles begin to show outward signs of heat stress at temperatures above 38 C (100 F), although they are able to cope to some extent by panting and evaporative cooling due to frothing at the mouth and/or expulsion of their bladder contents onto their hind legs. Both hot spells and droughts may be weathered by seeking shelter underground or in streams; Box Turtles can remain inactive for periods of up to weeks during the summer (S. Hall, pers. obs.), possibly constituting a form of aestivation.

Adaptations to Natural Disturbances: Box Turtles are unlikely to outrun fast-moving catastrophic events such as fires or floods and may be highly vulnerable if caught in one. However, they can survive longer-term adverse events such as heat waves and droughts by remaining semi-dormant in burrows or under leaf litter or partially submerged in shallow streams for long periods of time (S. Hall, pers. obs.). The return of rainy weather usually triggers a large resumption in surface activity.

Biotic Relationships: Box Turtles are highly omnivorous and opportunistic, feeding on primarily on the fungi, slugs and land snails, earthworms, insects, salamanders and other small vertebrates they encounter in their travels across the forest floor. They also feed on carrion and, in some cases, the scats of other animals (Hall, 1987; Dodd, 2001). Fruits and berries are heavily consumed whenever available and the foliage, seeds, and shoots of some species have also been reported in their diet (see Dodd, 2001, for a thorough review. Box Turtles, in turn, are the prey of mammalian carnivores and snakes, particularly as eggs, juveniles, and small adults. The fact that they are highly vulnerable when young is the likely explanation why so few are seen on the surface until they have reached the age of three or more, when the carapace has developed its dome shape and the plastron is capable of closing. Large adults, in comparison, are more capable of surviving the attacks of dogs, foxes, raccoons and other predators, as is attested by the scars they often bear on their shells. Even the adults, however, are not immune to the attacks of parasites and various diseases. Dodd (2001) lists a wide range of ecto- and endo-parasites of Eastern Box Turtles, as well as a number of bacterial diseases, mainly involving the respiratory system. He notes that few mass mortality events, if any, have been linked to disease outbreaks, at least with respect to the pathogens that they have long been exposed to and have had a chance to become adapted. Several emerging diseases have recently been discovered that may be having much more serious impacts (see Introduced Species below).

Life History and Autecology

Breeding and Courtship: Unlike other vertebrates, Box Turtles lack a distinct mating period or mating sites; evidence of any advertisement of mating receptivity is also slight, if any exists at all. Instead, Box Turtles mate -- or at least attempt to do so -- on an opportunistic basis throughout their active period during the year, whenever a male encounters a female. Adaptations that make this diffuse mating system work include male possession of active sperm throughout the year and the ability of the females to store sperm for at least several years (see Dodd, 2001, for a review). Courtship behavior by the males appears to be fairly uncomplicated, involving shoving or biting at the edges of the females' shells. Given the precarious nature of the mating event -- especially for the males, who risk toppling onto to the backs of their shells during the process -- female cooperation is entirely necessary for successful mating.

Reproductive Mode: Whereas mating can take place at random times during the year, nesting occurs primarily in early summer; in North Carolina, nesting (or presumed nesting journeys) have been observed several times in June (Hall, 1987). In one of these cases, the female nested in an old sawdust pile situated in an overgrown clearing within her home range. In another case, the female traveled three years in a row over distances of about 0.5 miles from the forested ridge-top where her home range was located to an overgrown old field where she presumably nested (in all three years, she was lost from sight after entering a massive tangle of Multiflora Roses). Careful choice of nesting sites, often involving re-use of previously used sites, appears to be a common feature in Box Turtle reproduction (see Dodd, 2001, for a review). From 1-7 eggs are usually laid, with larger females tending to lay larger clutches. Hatching typically occurs in the fall, although hatchlings may sometimes overwinter in the nest. As in other species of turtles, sex is determined by the temperatures experienced in the nest: cooler temperatures favor development of males, warmer temperatures females (see Dodd, 2001 for details).

General Ecology

Population Ecology: Eastern Box Turtles are excellent examples of species (k-strategists) that maximize individual survival, maintaining stable populations over long periods of time, rather than maximizing reproduction, with populations undergoing boom and bust fluctuations through time (r-strategists). Survival of eggs and young, in fact, is probably so low that the adults need to live for a very long time, reproducing for a period of decades, just to maintain a stable number of individuals within a given population. Such species, in turn, are associated with very stable habitats, where the carrying capacity (abbreviated by "k") -- as reflected in resource availability as well as environmental conditions affecting survival, varies only slightly. The great longevity of the adult turtles, together with their extreme investment in maintaining long-term home ranges, are attributes associated with this strategy of survival. On the flip side, such species are highly vulnerable to environmental disruptions: any change in habitat conditions that affects adult survival cannot be countered by a rapid build-up in population due to increased reproductive effort.

Community Ecology: A key to the slow-paced, low energy life-style of Box Turtles is their ability to consume a wide variety of food items, many of which -- such as poisonous fungi, carrion, and scats -- are inedible or avoided by other species, or are insufficient energetically to support competing species. Although they are highly tied to the detritivore food web for their routine diet, they also make opportunistic use of occasional food bonanzas provided by berries and other fruit, representing the plant-herbivore food web. Competitors include omnivorous mammals and birds, such as Opossums, Wood Thrushes, and Wild Turkeys, as well as forest-floor specialists, such as shrews. As ecotherms, however, these species have greater energy requirements than Box Turtles, and cannot make as effective use of the smaller, less energetic food items that make the large proportion of their diet.

Adverse Environmental Impacts

Effects of Introduced Species/Induced Increases of Native Species: While Raccoons are natural predators of Box Turtles, the artificial build-up of Raccoon populations near human developments may have significantly increased impacts to turtle populations. The arrival of Coyotes in North Carolina is also likely to increase the risk of predation, including to larger individual turtles. The spread of feral hog populations may be most devastating of all, since adult hogs have been shown to consume even adult Box Turtles (Dodd, 2001). In addition to long-established bacterial diseases, Box Turtles appear to be susceptible to Ranavirus, an emerging threat that appears to be responsible for mass mortality events observed in Georgia, Texas, and Illinois (Johnson et al., 2008; Adamovicz et al., 2018).

Status in North Carolina

NHP State Rank: [S4]

Global Rank: G5

Populations: Prior to the conversion of vast tract of Eastern Deciduous Forests to agriculture and human settlements, Box Turtles probably had just a single, well-connected, vast population spanning the entire area now identified as North Carolina. As forests have been converted and/or fragmented, however, Box Turtles probably occur within a multitude of more-or-less isolated population units. In some areas -- particularly isolated areas of upland forests -- little, if any, gene flow or exchange of individuals is now taking place. On the other hand, areas where forested floodplains still exist may still be linked into fairly substantial units, although even in these areas, construction of large reservoirs -- particularly where surrounded by residential development -- may limit connectivity between occupied sites. Currently, the number and extent of separate Box Turtle populations cannot be estimated within the state.

Protected Lands: Box Turtles have been recorded in ten state parks (DPR NRID, accessed 2021-05-16) but undoubtedly occurs in most, if not all of the park units. It also occurs in the Great Smoky Mountains National Park (Tilley and Hughey, 2010) and probably all other National Parks, National Forests, National Wildlife Refuges. In addition to State Parks, populations exist within most, if not all, state game lands, state forests, Coastal Reserves, and Dedicated State Natural Areas. All of these are managed, at least to some extent, to preserve large tracts of natural habitat, although some areas may also be managed for resources extraction.

Status Comments: Box Turtles are still widespread in North Carolina and occur in a wide range of common habitats. While the chances of extirpation are extremely low, it is at the same time not clear that there are any individual populations that are totally secure. Certainly, many populations are declining throughout the state, particularly due to habitat loss and fragmentation, and the spread of new diseases, such as Ranavirus, may imperil populations even within the most well-protected areas of natural habitat. For that reason, we believe a state rank of S4S5, implying at least some lack of security for all populations, is warranted, rather than a straight rank of S5 which implies complete security for one or more populations in the state.

Photo Gallery for Terrapene carolina - Eastern Box Turtle		125 photos are available. Only the most recent 30 are shown.
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	Recorded by: K. Sanford, J. Plough, M. Boyd Camden Co. Comment:	Recorded by: J. Mickey Surry Co. Comment:
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	Recorded by: Alina Martin Macon Co. Comment:	Recorded by: Alina Martin Macon Co. Comment:

Terrapene carolina - Eastern Box Turtle

Photo Gallery for Terrapene carolina - Eastern Box Turtle

125 photos are available. Only the most recent 30 are shown.