This small (to 12.5 cm), blue-black turtle has round yellow spots on its broad, smooth, keelless, unserrated carapace. These spots are transparent areas in the scutes, overlying patches of yellow pigment; they may fade with age, and some old individuals are spotless. The ventral surface of the marginals is yellowish and may have a pattern of black blotches at the outer edge in the young; the bridge is marked with an elongated black mark. Vertebral 1 is usually longer than or as long as broad; the other four vertebrals are broader than long. The yellow or slightly orange plastron has large black blotches on the outer parts, which sometimes cover the entire plastron in older individuals. The plastral formula is: an > abd >< pect > gul > fem > hum; there is a posterior notch on the hindlobe. The black head is moderate in size with a nonprojecting snout and a notched upper jaw. A broken yellow band is present near the tympanum, and another may extend backward from orbit; yellow spots may adorn the crown. Other skin is gray to black, and occasional yellow spots occur on the neck and limbs.
Diploid chromosomes total 50: 8 pairs of macrochromosomes with median to submedian centromeres, 5 pairs of macrochromosomes with terminal to subterminal centromeres, and 12 pairs of microchromosomes (Bickham, 1975, 1976).
Males have tan or black chins; brown eyes; long, thick tails with the vent near the tip; and slightly concave plastra. Females have yellow chins, orange eyes, and flat or convex plastra, which are slightly longer than those of the males and extend closer to the carapacial margin.
Clemmys guttata ranges from southern Ontario, Quebec, and Maine southward along the Atlantic Coastal Plain and Piedmont to Central Florida (Barnwell et al., 1997), and westward through Ontario, New York, Pennsylvania, central Ohio, northern Indiana, and Michigan to northeastern Illinois.
No subspecies have been described. Morphological variation between spotted turtle populations is not significant (Laemmerzahl, 1990), but differences exist in the light pigmentation (cream, yellow, orange, or pinkish) and the size of the light blotch on the side of the head. Parker and Whiteman (1993) found that within population genetic variation varies with the population density and size of the wetland habitat. Those from small populations in small isolated wetlands were less diverse than those from higher populations in more extensive wetlands.
Spotted turtles occupy a wide variety of shallow wetland habitats including swamps, marshes, bogs, fens, wet pastures, the edges of Carolina bays, vernal pools, permanent ponds, and small woodland streams and brooks. Habitat requirements include soft substrate and some aquatic vegetation. At certain times of the year, upland, moist terrestrial sites are used for aestivation and hibernation (Ward et al., 1976; Graham, 1995; Perillo, 1997).
Both sexes mature by the time they grow to a carapace length of 8 cm, probably in about 7-10 years (Ernst, 1970b; Ernst and Zug, 1994). The sexual cycles of both sexes in southeastern Pennsylvania were studied by Ernst and Zug (1994). At the time males emerge from hibernation in March, the spermatogenic cycle is at a low ebb. The spermatogenic cycle remains in regression during April, but activity begins in May when the spermatogonia are actively dividing and the primary spermatocytes form 2-4 layers in the wall of the seminiferous tubules. By July, some lumens are packed with secondary spermatocytes and small clusters of transforming spermatids, suggesting that some spermiogenesis occurs as the germ cells move downward through the tubules. Aggregations of spermatozoa occur in Sertoli plumes embedded in the germ cell layers, not in the lumens. Spermatogenesis and spermiogenesis conclude in August, and the sperm begin to move into the epididymides in September. Commonly mature female C. guttata with or without oviducal eggs possess four different size classes of follicles: I—< 2.0 mm diameter, pre-vitellogenic; II—2.0-5.9 mm. early vitellogenic; III—6.0-9.9 mm, mid-vitellogenic; and IV—10.0 mm or larger, late vitellogenic phase. These classes encompass the observed follicle groups without any female having a group of follicles overlapping two classes. Shelled oviducal eggs occurred only in May, Late vitellogenic follicles occurred in April-June and August females, and mid-vitellogenic follicles in April-May and September females. All females had class I and II follicles.
Mating begins in March in the south and the breeding season continues to June in the north. Courtship includes frantic chases of the female by one or several males. The chase may cover 30-50 m and last 15-30 min. and takes place in shallow water and on the adjacent land. The female's hindlegs and tail are sometimes bitten during the chase. When the female is finally caught the male mounts her from behind, and, while tightly grasping her carapace, places his tail beneath hers. At times the male slides off and comes to lie on his side; such copulating pairs form an L-shaped figure. Copulation is usually underwater, but may occur on land (Ernst, 1967c, 1970b).
Nesting lasts from May to July, varying with latitude. Nest sites include grass tussocks, hummocks of moist sphagnum moss, and the loamy soil of marshy pastures or stream banks. Nesting occurs either in the morning or in the evening. The flask-shaped nests are 4.5-6.5 cm deep with a chamber 4.5-5.4 cm wide.
One to two clutches of 1-8 eggs are deposited each year (Wilson, 1989; Ernst and Zug, 1994). Egg dimensions are as follows: length 25.0-33.7 mm, width 15.9-18.5 mm. The eggs are elliptical, white, and have a flexible membraneous shell. The natural incubation period may last 73-83 days (Ernst, 1970b). In southeastern Pennsylvania, the young emerge from late August to November, but some hatchlings overwinter in the nest.
Hatchlings are blue black and usually have one yellow spot on each carapacial scute except the cervical, which has none; some hatchlings lack spots. The yellow plastron has a black central figure. The head is spotted and in some the neck is spotted as well. The carapace length is 28.0-31.2 mm, carapace width 28.5-33.1 mm; plastron length is 25.2-26.9 mm, and plastron width 15.8-16.3 mm. The head and the tail are larger in proportion to shell length than those of adults.
Clemmys guttata is omnivorous. Surface (1908) found animal food in all 27 stomachs he examined and vegetation in three. The animals eaten included worms, slugs, snails, small crustaceans, crayfish, millipedes, spiders, and insects of the orders Ephemerida, Plecoptera, Odonata, Hemiptera, Neuroptera, Lepidoptera, Coleoptera, Diptera, and Hymenoptera. Many of the insects were not aquatic species; perhaps these were captured on land or had fallen in the water. Conant (1951a) observed C. guttata eating frogs, earthworms, grubs, and the grass growing in a flooded meadow. Pennsylvania specimens examined by us contained only filamentous green algae in their stomachs. Our captive specimens feed well on fresh and canned fish, cantaloupe, and watermelon.
Spotted turtles prefer cool temperatures. Ernst found them mating at cloacal temperatures of 8-10°C; that is at, or below the minimum voluntary temperatures of other aquatic turtles. During the warm summer they are not easily found; they aestivate in the mud bottom of waterways or in muskrat burrows or lodges. Some also aestivate on land. In winter, C. guttata hibernates in similar sites.
IUCN Red List Status (1996)
Vulnerable (A1cd+2cd). Populations of spotted turtles have declined in many areas in recent years due to modification and drainage of wetlands and collecting for the pet trade. They are protected or regulated in many states and provinces within their range.