(Holbrook, 1838)
Blanding's turtle
Recognition
This medium-sized (to 26 cm) turtle has an elongated, smooth carapace that is neither keeled nor serrated. Its vertebrals are broader than long, and the 1st touches four marginals and the cervical. Neurals are six sided and shortest anteriorly. The carapace is blue black; each pleural and vertebral has tan to yellow irregularly shaped spots or slightly radiating lines, and the marginals are heavily spotted. A movable hinge lies between the pectoral and abdominal scutes, but this hinge varies greatly in flexibility between individuals; in some Blanding's turtles it is almost as efficient as that of box turtles (Terrapene), while in others it is almost non-functional. The entoplastron is intersected by the humero-pectoral seam. The plastral hindlobe bears only a slight posterior notch; the plastral formula is: an > gul >< abd > fem >< hum > pect. There are no plastral buttresses, and the plastron is connected to the carapace by ligaments. The plastron is yellow with large, dark, symmetrically arranged blotches, which may be so large as to hide most of the yellow pigment. The flattened head is moderate in size with a nonprotruding snout and a terminally notched upper jaw. The eyes protrude. There is a bony temporal arch. The orbito-nasal foramen is small, but the posterior palatine foramen is large. The inferior process of the parietal touches the palatine. Triturating surfaces of the jaws are narrow and ridgeless; the upper surface has no contributions from the palatine or pterygoid. The skull is similar to that of Deirochelys (McDowell, 1964). The top and sides of the head are blue gray with tan reticulations, and sometimes yellow spots, especially in juveniles; the chin and throat are bright yellow; and the upper jaw may be marked with dark bars. Other skin is blue gray with some yellow scales on the tail and legs. The neck is very long, and the toes are webbed.
Stock (1972) reported the karyotype is 2n = 50: 20 metacentric or submetacentric, 10 subtelocentric, and 20 acrocentric or telocentric chromosomes.
Sexual dimorphism is not pronounced. In males, the tail is more robust, with the vent beyond the carapacial margin, and the plastron is slightly concave.
Distribution
Blanding's turtle ranges from southern Ontario south through the Great Lakes region and west to western Nebraska, Iowa, and northeastern Missouri. It also occurs in scattered localities in eastern New York, Massachusetts, southern New Hampshire, Maine, and Nova Scotia.
Habitat
Emydoidea lives in productive, eutrophic habitats, with clean shallow water, a soft but firm, organic bottom, and abundant aquatic vegetation. It is found in lakes, ponds, ephemeral pools, marshes, creeks, wet prairies, and sloughs. In Wisconsin, it spends most of its time in marshes rather than ponds, but marshes are used less than expected based on habitat availability, as also are terrestrial habitats, and ponds with sand bottoms and no aquatic vegetation are rare used (Ross and Anderson, 1990). Wet lands covered with cattail (Typha) mats are not used either, but areas cleared of cattails by muskrats (Ondatra zibethica) are entered, possibly for foraging.
Natural History
Size and age of maturity vary among populations and individuals. Males mature at plastron lengths of 17-19 cm in about 12 years (Graham and Doyle, 1977; Kofron and Schreiber, 1985). Females are first reproductively ready at plastron lengths of 15-21 cm in 14-20 years (Cogdon and Van Loben Sels, in Ernst et al., 1994).
Mating occurs from March to November, but is most common in the spring. There is little formal courtship behavior; males force the females to the bottom, mount almost immediately, grasping the female's shell with the claws of all four feet, and bring the tails together for cloacal contact. Some chin rubbing by the male may occur (Congdon et al., 1983b; Baker and Gillingham, 1983).
Nesting (nocturnal) occurs from late May to early July (Rowe and Moll, 1991). The nest may be 18 cm deep with an 18 cm wide egg chamber. Apparently, only one clutch is laid a year, and not all females nest each year (Congdon et al., 1983b).
A clutch contains 3-22 (usually 10-15) ellipsoidal (28.0-40.7 x 17.7-26.0 mm), dull white, hard-shelled eggs (Rowe, 1992; Congdon and Van Loben Sels, in Ernst et al., 1994). Most hatchlings emerge in September and incubation may take 73-112 days (Moriarty and Linck, 1995), but some individuals may hatch and then overwinter in the nest.
The rounded, keeled, hatchling carapace is dark brown to black, sometimes with spots, and 29.0-38.8 mm in length. After emergence hatchlings may use olfactory cues to find wetlands, and the entire journey may take several hours to nine days (Butler and Graham, 1995). The plastron has a large, black central blotch, and thefuture hinge is suggested by a crease. Hatchlings spend much time in cryptic forms among mosses, leaf litter and grass tussocks, both in day and night during temperature extremes.
Natural food includes [l][m]Glossary[/m][r]crustacea[/r]crustaceans, fish, frogs, tadpoles, snails, leeches, insects, and some aquatic plants. They often feed at night during warm weather. Prey may be stalked slowly, then seized suddenly with a quick strike of the long neck.
Remark
Bramble (1974) has shown that Emydoidea is most closely related to Emys and Terrapene, rather than Deirochelys, as was previously believed. His conclusions were based on a shared plastral closing mechanism and other morphological similarities. He thought Emydoidea convergent with Deirochelys in several features related to similar feeding systems.
IUCN Red List Status (1996)
Lower risk: near threatened. Numbers of Blanding's turtles have greatly declined in some places, particularly in disjunct populations. Even in their core range, wetland drainage, road mortality, and collecting have reduced populations. Many states have granted this species legal protection.