Description
BRIEF SUMMARY: Shell hard, somewhat flattened; upper shell black and usually with scattered rounded yellow spots; yellow or orange spots on head and neck; lower shell yellow or yellow-orange with a large black blotch on each scute. Maximum upper shell length about 13 cm. Mature male: vent located beyond rear edge of upper shell with tail extended; chin tan or dark; lower shell concave. Mature female: vent at or inside rear edge of upper shell with tail extended; chin yellowish. Hatchling: usually one yellow spot on each large scute on upper shell.
MORE DETAILS: A small black turtle with small, round, yellow spots on the broad, smooth, keelless carapace; small and old individuals sometimes are spotless; some individuals have growth layers evident on the carapace scutes; plastron is yellow or yellow-orange and has a large black blotch on each scute; head is mostly black with scattered yellow spots and blotches; limbs are gray to black above and often have yellow spots; the skin under the legs and neck is orange or pinkish (Harding and Holman 1990); males have a tan chin, brown eyes, slightly concave plastron, and (in adults) a long thick tail with the vent well beyond the posterior end of the carapace; females have a yellow chin, orange eyes, a flat or convex plastron, and a short tail with the vent under the posterior marginals; carapace length is 12.5 cm or less (Ernst et al. 1994). Males, at 80 to 89 mm in plastron length, average 155.5 g; females, at 90 to 99 mm in plastron length, average 174.7 g (Ernst 1975). Hatchlings are blue-black and usually have one, more than one, or no yellow spots on each carapacial scute; plastron is yellow with a black pattern; head is spotted and sometimes the neck is spotted; average dimensions are 29.8 mm carapace length, 31.3 mm carapace width, 26.4 mm plastron length, and 16.0 mm plastron width (Ernst 1970). Juveniles are black and may lack or have reduced spotting on the shell.
The eggs are smooth, white and elliptical. Nests generally are about 2 inches deep, 2 inches wide near the bottom, and one inch wide at the top (Ernst 1970).
Habitat
Spotted turtles inhabit mostly unpolluted, shallow bodies of water with a soft bottom and aquatic vegetation, such as small marshes, marshy pastures, bogs, fens, woodland streams, swamps, small ponds, vernal pools, and lake margins; in some areas they occur in brackish tidal streams.. Ponds surrounded by relatively undisturbed meadow or undergrowth are most favorable. These turtles favor waters with a soft bottom and aquatic vegetation. They often bask along the water's edge, on brush piles in water, or on logs or vegetation clumps. Often they move seasonally among different wetland types and may spend significant time on land during summer.
Cold season hibernation occurs in the muddy bottoms of waterways or bogs in communal hibernacula. Hibernacula usually have water depths of 55 to 95 cm (22 to 37 in) with a slow but steady flow or drift of water through densely vegetated wetlands with a deep, soft, mucky substrate (Carroll, pers. comm.). Muskrat burrows in Pennsylvania were used as winter hibernacula, nocturnal sleeping sites, refugia from danger, and estivation sites during the warm dry months (Ernst 1976). In Massachusetts, radio-tagged individuals hibernated in red maple-sphagnum swamps, then moved in late March to upland vernal pools, where they spent 3-4 months, then left the pools in August and spent 4-14 days in secluded terrestrial sites, then completed the move back to the swamps in August (Graham 1995). Hibernation occurred exclusively in bogs in central Ontario (Haxton and Berrill 1999) and in sphagnum swamps on an island in Georgian Bay, Ontario (Litzgus and Brooks 2000). See Lewis and Ritzenthaler (1997) for characteristics of hibernacula and hibernacula use in a fen in Ohio. Litzgus and Brooks (2000) documented seasonal changes in habitat selection in Ontario.
Eggs are laid in well-drained soil of marshy pastures, in grass or sedge tussock or mossy hummocks, in open areas (e.g., dirt path or road) at edge of thick vegetation, or similar sites exposed to sun. Sandy, sparsely vegetated strips and washouts along agricultural field edges are favorable for nesting (Carroll, pers. comm.). In South Carolina, gravid females spent a considerable amount of time on or at the edge of a powerline right-of-way, and they nested on the edge of the powerline and in relatively recent clearcuts (Litzgus and Mousseau 2004).
New Hampshire: deep-muck, densely vegetated scrub-shrub swamp or emergent marsh habitats that are edgewaters or backwaters of low-gradient reaches of permanent streams with moderate to slow flowages, and water depth of 10 to 50 cm (Carroll, pers. comm.). Rhode Island: reported from salt marshes and small bogs or ponds with adjacent dry upland oak-pine forest (DeGraaf and Rudis 1983). Florida: woodland or meadow streams with sphagnum. Indiana: thoroughly aquatic, said to inhabit bogs by Smith (1961); also has been collected in shallow inlets of lakes, grassy marshes, drainage ditches, and woodland ponds, and is rarely found in flowing water (Minton 1972). Maine: unpolluted, small, shallow wetlands surrounded by dense vegetation such as slow streams, ponds, vernal pools, bog ponds, roadside ditches, and wet meadows (Hunter et al. 1992). Vermont: areas of highbush blueberry/red maple swamps, and in kettle basin shrub swamps (Fichtel, pers. comm.).
Ecology
The spotted turtle is usually solitary but may be found in large aggregations in suitable feeding areas or at basking sites (Ernst 1976). In Pennsylvania, population density was estimated at 15-32 per acre (Ernst 1976). The population had a 1:1.46 male to female ratio and a 1:2.09 juvenile to adult ratio. Out of a total of seven different species of turtles captured in the mark-recapture study, Clemmys guttata was the second most abundant turtle comprising 10.2 percent of the total. Another turtle in this study, Chrysemys picta, had a population density of 239 individuals per acre. In two sites in Massachusetts, density was estimated at 0.2 and 1.4 adults per ha (Milam and Melvin 2001).
In Pennsylvania, Ernst (1976) found there to be a commensal relationship between spotted turtles and muskrats. Many turtles were dependent on the bank burrows of the muskrat, with the burrow forming the center of the home range.
In Maine, fish are believed to be competitors for food with the spotted turtle, and painted turtles are believed to compete for space (McCollough, pers. comm.). There is an overlap of habitat use and seasonal movements between adult spotted turtles and subadult Blanding's turtles; competition for food or space may or may not be a problem (Carroll, pers. comm.). Occasional juvenile common snapping turtles and adult eastern painted turtles appear in spotted turtle microhabitats and may compete for food (Carroll, pers. comm.).
Predators include foxes, skunks, and raccoons (Ernst 1976; McCollough, pers. comm.). Hatchlings and juveniles are eaten by many birds and small mammals such as shrews (Harding, pers. comm.).
Parasites include leeches (Placobdella sp.) that attach to limb sockets, tails, and plastrons (Ernst 1976). Leeches were found on spotted turtles just out of hibernation, suggesting that leeches overwinter attached to the turtles (Carroll, pers. comm.).
Reproduction
Mating occurs March-May, typically during cool weather (Ernst 1982). Eggs are laid late May-early July (mostly June) (Ernst 1967). Nest digging lasts 29 to 75 minutes (Ernst 1970); egg-laying and covering of the nest may last well into the night. All-night nesting has been documented in Illinois (Carroll, pers. comm.).
Clutch size is 1-8, with an average of 3-5 (Adler 1961, Ernst 1970); mean clutch size is larger in the north than in the south (Litzgus and Mousseau 2003). Usually one clutch is laid each year (Ernst 1967), but some females may produce 2 clutches/season (Herp. Rev. 20:69). In South Carolina, 5 of 12 gravid females produced second clutches and 1 produced a third (Litzgus and Mousseau 2003). Incubation requires 45 to 83 days, depending on nest temperature.
Hatching occurs in late August to September (Fineran 1948, Ernst and Barbour 1972, Ernst et al. 1974, Harding and Holman 1990). Rarely, hatchlings from late nestings may overwinter in the nest, emerging the following spring (Ernst 1975). Growth of the hatchlings the first season depends on the date of emergence from the nest, varying from 4.2 to 17.5 mm (Pennsylvania; Ernst 1975).
Growth after the first season varies, with the smallest individuals growing the fastest (Ernst 1975). The growth rate decreases as the turtles increase in size; adults grow at a rate of 2 to 3 percent each year (Ernst 1975). In Rhode Island, mean plastral length increased 7.5 mm per year from the first through the fifth year of growth (Graham 1970). The annual growth rate declined each season from the second to the sixth and then increased in the seventh preceding the attainment of sexual maturity.
Age of sexual maturity is probably more closely related to reaching a specific size than age, although this length is usually obtained by 10 years of age (Ernst 1975). Sexual maturity may take longer to achieve in the north than in southeastern Pennsylvania, where females are sexually mature in about 7-9 years, males in 7-10 years (Ernst, 1994, J. Herpetol. 28:99-102). Males reached maturity at a minimum plastron length of 83.4 mm; in females the minimum was 80.8 mm (Ernst and Barbour 1972).
The maximum life span of adults is at least 26 years but may be as high as 50 (Tyning 1990). The longevity of a captive recorded by Pope (1939) was 42 years, and Graham (1970) recorded a 26-year-old turtle found in the wild. In Pennyslvania, prenatal mortality eliminated 32 percent of the eggs per clutch and postnatal mortality reduced the progeny to still a smaller number (Ernst 1976); egg survivorship to hatching in Pennsylvania was 0.58 (Iverson 1991); reproductive potential was 2.4 young per clutch (Ernst 1976); estimated average annual mortality for juveniles was 45%.
As is true of most turtles, spotted turtles have temperature-dependent sex determination; eggs incubated at 27 C or below produced a large percentage of males whereas those incubated at 30 C produced all females (Ewert and Nelson 1991).