Eastern Box Turtle

Species Description

Box turtles are a widely occurring group of land-based turtles across the United States. Adult Eastern Box Turtles (Terrapene carolina carolina) are typically 13-15 cm (5-6 inches) long (Jensen et al., 2008) with striking shells. The carapace can vary in color and pattern but most typically is a dark brown or black with yellow orange blotches. The color scheme and patterns of their shells help them blend into the leaf litter of the forest floors where they spend their time. 

Like their shells, their limbs and faces are also dark brown or black with yellow orange blotches. Typically, Eastern Box Turtles have four toes on their hindfeet, but some southern populations may have three (Jensen et al., 2008).  

A key feature of box turtles is the singular hinge on their plastron that allows them to be fully enclosed within their shells. Adding to their box-like appearance, their shells are higher and more domed as compared to aquatic turtles who are more streamlined for moving through water. 

There are several ways to distinguish male from females. Plastrons of males are typically concave, which makes mating easier. Males also tend to have flared carapace edges. Males have shorter rear claws while females have longer, straighter rear claws which allow for nest digging.  Females may have dark brown eyes while males may have red eyes, however difference in eye color is a less reliable characteristic than shell features and claw length (Jensen et al., 2008).

Taxonomy

The Eastern Box Turtle was first described in 1758 by Carl Linnaeus, the biologist credited with the naming convention we use for species today. Unlike many other species, the Eastern Box Turtle has retained the name given to it by Linnaeus (Terrapene carolina carolina) but there are multiple other sub-species. The other members of Terrapene carolina include the Three-Toed Box Turtle (T.c. triunguis), the Gulf Coast Box Turtle (T.c. major), and the Florida Box Turtle (T.c. bauri). 

Distribution

Members of Terrapene carolina occur widely throughout the eastern United States. The Three-Toed Box Turtle stretches from the western portion of Texas through Mississippi and up to Missouri. The Eastern Box Turtle can be found from Tennessee and the northern portions of Alabama and Mississippi to the East Coast.  The northern part of their range reaches Michigan and Massachusetts. As the name suggests, the Florida Box Turtle is primarily found in Florida. The Gulf Coast Box Turtle has the smallest range of all, occurring only along the coasts of Louisianna, Alabama, Mississippi, and Florida.

Habitat

Eastern Box Turtles live their lives largely out of water. They can be found in a variety of habitats such as open forest, fields, and riparian areas (Kiester & Wiley, 2015).  Within their habitat, they can be found near structures like bushes or clumps of vegetation and downed logs. Such structures offer protection and refuge from midday heat. 

Ample vegetation is a necessity for brumation, a common adaptation for reptiles living in cold environments that allows them to drastically slow their metabolism and remain dormant underground until spring. Many reptiles brumate below the frostline to stay at safe over-wintering temperatures but Eastern Box Turtles brumate quite shallowly.  Often, they dig into holes just at the surface and ensure they are well covered with vegetation to provide some insulation (Claussen et al., 1991). Unique among North American turtles, the Eastern Box Turtle can also survive partial freezing at temperatures down to at least 3.6°C (25.5°F) (Currylow et al., 2012).

Movement and Home Range

Yearly activity of Eastern Box Turtles varies by latitude. Turtles in southern populations are active to some degree all year round and do not officially enter brumation. Northern populations will typically brumate from late October/early November to April (Kiester & Willey, 2015). Box turtles exhibit site fidelity for their hibernation locations and will return year after year. 

Daily activity of Eastern Box Turtles peaks in the mornings or evenings when the day is a bit cooler. Activity spikes also occur after rain. Home range size estimates are highly variable, seeming to largely depend on the individual, but are typically between around 2-7 hectares (5-17 acres) and don’t appear to differ by sex (Kiester & Willey, 2015).

Diet

Eastern Box Turtles are omnivorous and eat fruits, seeds, slugs, insects, worms, and even scavenge carrion. Turtles may act as important disperses for fruiting plants as they pass the seeds from fruits they eat into new locations and increase germination rates (Braun & Brooks, Jr., 1987; Liu et al., 2004).

Reproduction

Mating occurs from April to June while nesting occurs later in the summer. Within southern populations, mating may occur again in the fall. Female Eastern Box Turtles typically lay 1-10 eggs per clutch (Kiester & Willey, 2015). Because females in southern populations may mate multiple times a year, they may lay up to 3 clutches in one year (Jensen et al., 2008). While northern populations may produce fewer clutches, they lay more eggs per clutch (Wilson & Ernst, 2005). Hatchlings emerge from nests after about 2-3 months; however, they may overwinter in nests if hatching occurs late in the year (Jensen et al., 2008). Adults reach sexual maturity at 5-10 years (Jensen et al., 2008). Lifespan estimations vary but it’s clear Eastern Box Turtles can live to at least 50 (Henry, 2003) and some individuals have even been estimated at 100 (Cook et al., 2010). 

Eastern Box Turtles exhibit temperature dependent sex determination. Eggs in cooler conditions will produce male hatchlings while eggs in warmer conditions will produce females.

Conservation Concerns

Eastern Box Turtles are considered common and not a concern nationally, but their populations are declining. They are listed as endangered in New Hampshire and Maine.  They are listed as a species of special concern in Connecticut, Indiana, Massachusetts, Michigan, and Ohio. 

Habitat loss and fragmentation is a major concern for populations across their range. Conversion of natural habitats in favor of agricultural development reduces resources available to individuals. In addition, fragmented landscapes increase the chance for road mortalities as turtles seek appropriate habitat. 

Many forests throughout the United States are fire adapted and prescribed burns are required to keep forests healthy, but they pose a risk to turtles who are above ground. It is important to schedule burns for times when turtles are likely to be underground, usually in winter/early spring. 

Box turtles make popular pets and the striking colors on Eastern Box Turtles make them a particular target for collecting. Over-collecting can, and has had, detrimental effects on population sizes throughout their range. 

When it comes to natural threats, adults are at risk from predation by larger mesopredators while juveniles and eggs are also predated by snakes and birds (Jensen et al., 2008). Subsidized predators, such as raccoons and foxes, which are more abundant on the landscape due to human activity, can post a significant threat in some areas where they may consume the majority of nests.