Clemmys guttata is a very small species that rarely exceeds a straight-line carapace length of 11.4 cm (4.5 inches); the maximum recorded carapace length is 13.6 cm (5.4 inches). The adult carapace is smooth, without obvious growth ridges (annuli), and is black or brownish-black with a variable number of round yellow spots. These spots may fade in old adults, and occasional specimens lack carapace spots altogether. The plastron is yellow or orange with a black blotch covering a portion of each scute; in some male or old female specimens the black pigment can cover nearly the entire plastron. Growth rings (annuli) are usually visible on plastral scutes; counting these annuli is an unreliable method for determining the age of a mature specimen, though such a count may allow an estimate of a specimen's minimum age.
The head is mostly black, with a variable number of yellow spots; there is usually a large, sometimes divided, yellow or orange blotch on each side of the head. The upper jaw is notched medially. The upper surfaces of the legs and tail are black, again usually with a scattering of yellow spots, and the lower surfaces of the legs and neck are orange to pink or salmon-red.
The sexes are dimorphic, and easily distinguished in mature specimens. Males have a more elongate and compressed carapace, and a concave (centrally depressed) plastron. The male's eyes are typically brown, and the chin is tan, brown, or black. The male's tail is comparatively longer and thicker, with the vent (anal opening) beyond the edge of the carapace with tail extended. The female has a higher, more rounded carapace, and a flat plastron. The female's eyes are usually orange and her chin is yellow or orange. The female's tail is comparatively narrow, and when extended, the vent is at or beneath the edge of the carapace. Females are slightly larger than males, on average.
The hatchling Spotted Turtle has a nearly circular carapace from 2.5 to 3.1 cm in length; coloration above is like the adult but with only one spot per scute. The tail may be nearly as long as the carapace. Juvenile Spotted Turtles have more conspicuous scute annuli on their carapaces than do the adults (Ernst, Lovich, and Barbour, 1994; Harding, 1997).
The range of Clemmys guttata is roughly divided into two possibly discontinuous portions of eastern North America; the first extends along the eastern seaboard from southern Maine through New England and south through the eastern (largely coastal plain) portions of Virginia, the Carolinas, Georgia, and northern Florida. There are isolated populations recorded in southeastern Quebec and adjacent northern Vermont, and in the western Carolinas. The second (Great Lakes) portion of the range extends from northeastern Illinois into the western and southern Lower Peninsula of Michigan, northern Indiana, Ohio and western Pennsylvania, and across extreme southern Ontario into western New York. Isolated populations occur in central Indiana and the Georgian Bay region of Ontario (Barnwell et al., 1997; Bartlett and Bartlett, 1999; Conant and Collins, 1998; Ernst, Lovich, and Barbour, 1994; Harding, 1997).
Within this range, the Spotted Turtle is spottily distributed in the remaining suitable habitat, and most populations are small and colonial in nature. Generalized population declines and local extirpations have occurred, especially in the Great Lakes portion of the range, but more recently in the East as well (Klemens, 1993; Ernst, Lovich, and Barbour, 1994; Harding, 1997).
Spotted Turtles prefer shallow waters with a soft bottom substrate and some submergent and emergent vegetation. These can include sedge meadows, boggy ponds, fens, tamarack swamps, sphagnum seepages, and slow, muddy streams. These turtles also frequently wander on land between wetlands, and (as noted above) may aestivate on land for weeks at a time (Ernst, Lovich, and Barbour, 1994; Harding, 1997).
Spotted Turtles probably reach sexual maturity at an age of 7 to 14 years, at a carapace length of about 9 cm (3.5 inches), with northern animals probably taking longer to mature than those living farther south (Ernst, 1970; Harding, 1997).
Courtship and mating activity begins soon after emergence from winter dormancy; in Pennsylvania, Ernst (1982) recorded Spotted Turtle courtship at a water temperature of 8.5°C, while Ontario turtles were courting at a temperature of 2°C (Litzgus and Brooks, 2000). Male Spotted Turtles may fight each other, presumably over access to females. Courtship involves the male chasing the female under water while nipping and biting her legs and carapace; he then mounts her shell and bites at her head and neck. Copulation occurs in shallow water and may last for an hour (Ernst, Lovich, and Barbour, 1994; Harding, 1997).
Nesting can occur from late May through June. Females typically lay only one clutch of from 1 to 8 eggs per year, though a few may lay a second, smaller clutch a few days after the first. Captive females have been reported to lay multiple clutches and far more eggs in a year's time. One captive female from New York produced eight clutches in a thirteen month period, for a total of 42 eggs (J. Czech, pers. comm.). Such reports suggest that female Spotted Turtles are capable of a greater production of eggs than is normally seen in the wild, but are constrained by unknown environmental factors (such as a limited food supply or short activity season).
Nesting females seek open, sunny locations that offer moist, but well-drained, soils. If better sites are lacking, nests may also be placed in the tops of sedge hummocks or in accumulations of vegetation (such as decaying leaf litter). The nests are dug with the hind feet. The eggs, 2.5 to 3.4 cm long, are elliptical and have thin, flexible shells. Incubation requires from 44 to 83 days, with faster development at higher temperatures. Most young emerge from their nests in August or September, but overwintering in the nest has been reported (Ernst, Lovich, and Barbour, 1994; Harding, 1997).
The sex of the hatchlings is determined by nest temperature during the middle third of the incubation period; in the lab, cooler experimental temperatures ( 22.5° to 27°C) produced mostly males, and warmer temperatures (30°C) produced only females (Ewert and Nelson, 1991).
Spotted Turtles become active very early in the spring, and (as noted above) are often active at relatively cold water temperatures. Activity appears to peak during April and May in the northern part of the range. Spotted Turtles tend to become inactive in the warmest part of the summer (when water temperatures exceed 30°C) and they may aestivate aquatically or terrestrially for long periods of time. During summer dormancy, the turtles may burrow into leaf litter in woodlands or open fields or marsh edges; others remain in muskrat burrows or other aquatic refuges (Behler, 1996; Harding, 1997). Litzgus and Brooks (2000) have questioned the common presumption that summer dormancy is an attempt by the turtles to avoid high temperatures and desiccation; data from Ontario and elsewhere suggests that avoidance of predation and conservation of energy resources may be viable alternate explanations. The "winter" dormant period may commence in late summer or fall, but almost always after a return to aquatic habitats (Ernst, Lovich, and Barbour, 1994; Harding, 1997).
Spotted Turtles tend to occupy limited home ranges of about 0.5 to 3.5 hectares (1.2 to 8.6 acres). However,the total area of suitable habitat for a particular Spotted Turtle colony often does not exceed these areas, at least in the northern part of the range (Ernst, Lovich, and Barbour, 1994; Harding, 1997).
These little turtles are highly vulnerable to predation, especially during their frequent terrestrial wanderings. Many specimens will show mutilation injuries and scars from past predation attempts. Raccoons (Procyon lotor) are particularly adept at killing and consuming this species. When surprised while basking, Spotted Turtles will dive into the water and bury themselves in the bottom mud. Muskrats kill many Spotted Turtles during the winter dormant period (Harding, 1997).
Spotted Turtles eat a variety of plant and animal foods, which are consumed in the water. Feeding does not begin in spring until water temperatures reach about 15°C (Ernst, 1982). Vegetable foods include algae, leaves of soft aquatic plants, and water lily seeds. Animal foods include worms, mollusks, crustaceans, adult and larval insects, amphibian eggs and larvae, and carrion (Behler, 1996; Ernst, Lovich, and Barbour, 1994; Harding, 1997).
This turtle is harmless to human interests.
Clemmys guttata occupies a rather specialized ecological niche in habitats that are comparatively rare and biologically diverse. This small, brightly colored turtle is aesthetically appealing to humans, which unfortunately has resulted in a high demand for them in the commercial pet trade (see "Conservation" below).
The specialized wetland habitats used by Spotted Turtles have been widely drained and converted by humans into agricultural and residential land, or modified into more open aquatic habitats not favored Spotted Turtles. Many of the remaining Spotted turtle populations are now very small and isolated, with little or no opportunities for genetic exchange with other sites (this is especially the case in the Great Lakes area, but is true in other parts of the range as well). As these turtle "colonies" become increasingly isolated, they also become more vulnerable to human exploitation and to predation by "subsidized" predators such as raccoons (Harding, 1997, and pers. ob.).
Like its close relatives, the Wood Turtle (Clemmys insculpta) and Blanding's Turtle (Emydoidea blandingii), the Spotted Turtle exhibits certain life history traits that cause it be be unusually vulnerable to human exploitation and habitat degradation. These traits include: high egg (and probably hatchling) mortality, low reproductive potential under natural conditions, and delayed sexual maturity (7 -- 14 yrs), balanced by relatively long potential adult breeding life. Species with these traits will predictably require high annual survivorship of mature adults and older juveniles to maintain population stability. Any factor which reduces adult survivorship below expected natural levels (such as collecting or harvest by humans, road mortality, or an increase in predator numbers) will inevitably lead to a declining population, and perhaps eventual extinction of the population. It is thus reasonable to manage Spotted Turtles (and other long-lived turtle species) with the assumption that they have no harvestable surplus in their populations (Congdon et al., 1993, 1994; Harding, 1997). Most states and provinces do offer this species some degree of legal protection from exploitation, but protection is not yet consistent or universal over the turtle's range (Levell, 1997). Spotted turtles are listed as vulnerable on the IUCN's Red List, and they are considered threatened in the state of Michigan.
Recent taxonomic studies have confirmed that the subfamily emydinae is a natural group and includes the Spotted Turtle and its closest relatives in the traditional genera Clemmys, Emys, Emydoidea, and Terrapene (Bickham et al., 1996; Burke et. al, 1996; Feldman and Parham, 2001). However, recent revisions reveal that the traditional genus Clemmys was paraphyletic, and recommended placing the Wood Turtle ("Clemmys" insculpta) and the Bog Turtle ("Clemmys" muhlenbergii) together into the genus Glyptemys, leaving the Spotted Turtle as the sole remaining member of the genus Clemmys (Holman and Fritz, 2001; Feldman and Parham, 2002).
Ernst (1983) reported a hybrid between the Spotted Turtle and the Bog Turtle, Glyptemys (=Clemmys) muhlenbergii. These species are similar in size and overlap in habitat requirements.
James Harding (author), Michigan State University, James Harding (editor), Michigan State University.
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