In Canada and the United States, the Blanding’s turtle, Emydoidea blandingii (Family Emydidae), is officially designated as endangered or threatened in several provinces and a number of states. In many areas, it has become a “poster species” for attracting public interest in issues common to conservation of freshwater turtles in general. Over the past three decades, knowledge of Blanding’s turtle biology and ecology has increased dramatically, and among species with conservation concerns, it now ranks as one of the best known turtle species throughout much of its range. Blanding’s turtles seldom occur in dense populations such as those of sympatric painted turtles, but two large populations exist in southeastern Minnesota, and in north-central Nebraska. Individuals delay maturity from 14–21 yrs, and can attain ages greater than 75 yrs and still reproduce successfully. Most populations of Blanding’s turtles are threatened by collecting, road mortality, and the reduction and degradation of both aquatic and terrestrial portions of their core habitats. Adults of both sexes make extensive forays onto land to visit temporary wetlands, and adult females move overland on pre-nesting movements and to nest; both activities exposes adults to increased risk of mortality associated with roads, farm machinery, and terrestrial predators. Proposed conservation measures include: 1) methods to reduce road mortality (e.g., fencing and road passages); 2) elimination of commercial collecting; 3) protection of large resident wetlands and smaller ephemeral wetlands; 4) protection and management of adjacent terrestrial areas used for nesting and as corridors for movements among wetlands; 5) research on risks associated with the timing and duration of terrestrial movements of both sexes; and 6) where necessary, removal of nest predators. More extensive regional information can be found in Herman et al. (2003), COSEWIC (2005), and Congdon and Keinath (2006).

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Blanding's turtles are found from southwestern Quebec and southern Ontario west to Minnesota and central Nebraska and south to central Illinois. The Great Lakes region is currently a stronghold for this species (Harding, 1997). There are disjunct populations along the eastern seaboard as well, including in New York, Massachusets, Rhode Island, New Hampshire, southern Maine, and Nova Scotia (Ernst, Lovich, and Barbour, 1994).

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) Distribution is centered in the Great Lakes region; ranges from Minnesota, southeastern South Dakota, and central Nebraska eastward through Iowa, northern Missouri, northern and central Illinois, Wisconsin, Michigan (both upper and lower peninsulas), northern and southwestern Indiana, and northern Ohio to northwestern Pennsylvania, northern New York, southeastern Ontario, and southwestern Quebec, with disjunct populations in southeastern New York, eastern New England (Massachusetts to southern Maine), and Nova Scotia (mostly in Kejimkujik National Park; Herman et al. 1995). See Coffin and Pfannmuller (1988), Vogt (1981), Iverson (1992), Harding (1997), and map in Conant and Collins (1991). Spotty, low-density distribution. The bottomlands of the Upper Mississippi River near Kellogg in Wabasha County in Minnesota may support the largest breeding population in the entire range. This species was formerly more widespread. Archeological records show the species in central Missouri, southwestern Kansas and the Oklahoma panhandle during the Pleistocene as well as in Kansas during the late Pliocene (Kofron and Schreiber 1985, McCoy 1973). Probably there was enough moisture in these areas at that time to support marshes. The species prefers prairie marshes in the western and southern parts of its range, and it is thought that it migrated eastward to the Atlantic coast with other Prairie Peninsula reptiles during the dry period of the Holocene. Although it has been suggested (to explain the Nova Scotian population) that Emydoidea took refuge on the Atlantic Coastal Plain during glaciation (Bleakney 1958), it is more likely that the central plains area was the glacial refuge and post-glacial dispersal center (Preston and McCoy 1971) from which the turtles again moved east and north across the continent. A Kansan fossil dates from the interglacial period, early Yarmouthian. The northward movement of marshes since the retreat of the glaciers may explain the historic dearth of the species farther south in the midwestern states. Remains have been found farther south in Illinois and New York than the species is found today and dating from the time of Early Woodland habitations. A tool made of Emydoidea carapace has also been found in Quebec 125 miles north of the current range of the species. However, it is possible that trade which was extensive among the early Indian cultures may have brought the pieces into these regions (Preston and McCoy, 1971). In more recent times, the species was probably more widespread on the central prairies of Illinois, Iowa, and Kansas before the extensive wet prairie marshes were drained. Remains are common in archeological sites throughout the present range of the species (McCoy 1973). It has been suggested that the turtle does not inhabit more southern regions, in spite of the adaptive strategies of having eggs tolerant of dry conditions and relatively high temperatures, because of competitive interactions with other emydids (Gutzke and Packard 1987). However, Emydoidea blandingii has a very low maximum temperature tolerance (mean = 39.5 C, range 38.2 to 40.6 C) which probably restricts the turtle's range, and the egg adaptations allow the turtle to use dry, exposed nesting sites where there is reduced competition from other chelonians (Hutchison et al. 1966). A cool incubation environment that may result in developmental abnormalities and limit reproductive success (Standing et al. 2000) may restrict distribution and abudnance at the northern end of the range.

Continent: North-America
Distribution: Canada (S Ontario, SW Quebec, isolated populations in SC Nova Scotia),  USA (the Great lakes region, Michigan, NW Pennsylvania, N Ohio, N Indiana, Illinois, Wisconsin, Iowa, Minnesota, W Nebraska, Iowa , NE Missouri, in scattered localities in E New York, SC Connecticut, S Rhode Island, NE Massachusetts, S New Hampshire, SW Maine)  
Type locality: Fox River, Illinois.

Canada, USA. Distributed disjunctly from southeastern Ontario, adjacent Quebec, and southern Nova Scotia, south into New England, and west through the Great Lakes to western Nebraska, Iowa, and extreme northeastern Missouri.          

Distribution of Emydoidea blandingii in northern USA and Canada. Red points = museum and literature occurrence records based on published records plus more recent and authors’ data; green shading =  projected distribution based on GIS-defined hydrologic unit compartments (HUCs) constructed around verified localities and then adding HUCs that connect known point localities in the same watershed or physiographic region, and similar habitats and elevations as verified HUCs (Buhlmann et al., unpubl. data), and adjusted based on authors’ data.

 

Blanding's turtle are medium sized turtles with a carapace length ranging from 15.2 to 27.4 cm. These semi-aquatic turtles have moderately high, domed carapaces. They are elongate and smooth, lacking keels or sculpturing. The carapacial scutes display distinct growth annuli most prominently seen in juveniles. Coloration between individuals is highly variable. The carapace is black or gray with any variation of scattered light yellow or whitish flecks or dots. The light spots and flecks predominate in some individuals while others are almost solid black. The plastron is yellow in color with a dark blotch in the outer corner of each scute, and has a V-shaped notch near the tail. In males, the plastron is moderately concave while females posses a flatter plastron and a narrower tail. Blanding's turtles have a hinge located between the pectoral and abdominal scutes, which allows for partial closing of the plastral lobes. The hinge may be practically non-functional or nearly as effective as that of the box turtle (Terrapene). The head is rather flat with a short, rounded snout. These turtles seem to have a permanent "smile" due to the notch in the upper jaw. As with the carapace, the top and sides of the head vary in coloration from black, brown, or olive with yellowish spots or mottling. Contrasting greatly with the rest of the turtle, the chin, throat, and underside of the long neck are bright yellow. The hatchlings of this species have a gray, black, or brown carapace that is 3 to 3.5 cm long. A single light spot is seen in the center of each scute. The plastron has a central black blotch outlined in a yellowish color and the plastral hinge is not yet functional. Immature turtles are often more brightly marked than adults and possess a proportionately longer and thinner tail.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Length: 27 cm

Box turtles, Terrapene carolina and T. ornata, have a plastral hinge, but neither has a yellow throat and chin or a notched upper jaw; T. carolina has a keeled carapace. Clemmys guttata has a blue-black carapace with yellow spots, but it lacks the plastral hinge.

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

Blanding's turtles are found in and around shallow weedy ponds, marshes, swamps, and lake inlets and coves most of the year. They prefer slow-moving, shallow water and a muddy bottom with plenty of vegetation (Harding 1990).

Habitat Regions: temperate ; terrestrial ; freshwater

Terrestrial Biomes: forest

Aquatic Biomes: lakes and ponds

Comments: Marshes, ponds, swamps, lake shallows, backwater sloughs, shallow slow-moving rivers, protected coves and inlets of large lakes, oxbows, and pools adjacent to rivers; waters with soft bottom and aquatic vegetation (Kofron and Schreiber 1985, Nyboer 1992, Ernst et al. 1994). Sometimes leaves water and walks overland.

Although E. blandingii has been said to be semi-aquatic, this idea evidently is based primarily on observations of nesting females and has been questioned by several researchers (Pope 1939, Lagler 1943, Gibbons 1968, Kofron and Schreiber 1985) who regard this species as primarily aquatic. Gibbons (1968) found turtles on land between aquatic areas only in April and September (in addition to females in June). Conant (1951) considered it to be unusual for turtles in Ohio to be more than 100 yards from the water. However, Rowe and Moll (1991) found that terrestrial excursions were a significant part of activity in Illinois.

Hibernation most often occurs within organic substrate of ponds and creeks. Two turtles overwintered within 10 m of each other for 31 days in Wisconsin (Ross and Anderson 1990). Somewhat communal hibernation may be due to scarcity of suitable hibernacula. Five of the six overwintering turtles in the Wisconsin study used one of their summer activity centers for overwintering. Most moved from marshes, shallow ponds, and ditches to deeper ponds after September 1. The deeper ponds probably provide stable water levels during the critical overwintering period and a longer period of warm water temperatures in early fall. Individuals in Missouri hibernated in shallow marsh areas under 15 cm mud below 9.5-21 cm of water. One turtle in Illinois was observed wintering under a brush pile that she had used as a refugium during August (Rowe and Moll 1991) and, in Ohio, turtles have been reported overwintering beneath leaves several feet from the water (Conant 1951).

Eggs are laid usually in sandy soil in upland areas, usually in warm sunny sites. In Michigan, nests were 2-1115 m (average 135 m) from the nearest water; most females returned to same general nesting area each year; nesting area usually was not immediately adjacent to female's marsh habitat (Congdon et al. 1983). In Wisconsin, nested usually in grassland, average of 168 m from water and average of 620 m from non-nesting activity center (Ross and Anderson 1990). Wisconsin turtles nested in large (>6 ha) contiguous grassland habitat (Ross and Anderson 1990). About 50% of the cover at the Wisconsin nest sites was grasses and Pennsylvania sedge (Carex pensylvanica) (Ross and Anderson 1990). Illinois females wandered overland for 5-17 days and up to 1670 m away before nesting 650-900 m from their home ponds (Rowe and Moll 1991). Turtles in Nova Scotia were nesting 5 miles across a lake from their probable activity centers (Bleakney 1963). In Maine, nests were 70-410 m (mean 242 m) from the nearest water (Joyal et al. 2000). In Nova Scotia, nests were predominantly on lakeshore cobble beaches (Standing et al. 1999).

Females in Ontario chose areas with little or no vegetation (Petokas 1986). However, nests were found in a clustered distribution, likely because of herbaceous cover along the perimeter of the chosen site where turtles could hide and survey the area before advancing into the open to seek a nest site (Petokas 1986).

Like other freshwater and terrestrial turtles, Blanding's turtle often chooses disturbed sites. Petokas (1986) suggested that the turtles probably nested in available clearings, on sand and gravel bars, and on muskrat lodges or beaver lodges and dams prior to the modification of the landscape by humans. However, all of the females in his study chose disturbed sreas such as tilled plots, cemeteries, a powerline right-of-way, and a road. He found no nests on the available beaver dams.

In Massachusetts, turtles were observed crossing an area of open sandy soil to nest almost exclusively in the middle and far reaches of the light sandy soil of a cornfield frequently disturbed by tilling or earth-moving; such areas afforded the highest elevation (about 10 m above the marsh) and most open land near the marsh (Linck et al. 1989). Similarly, one of the earliest natural history reports of the nesting Blanding's turtle stated that the female nested on a sand hill 10 feet above the level of open water (Brown 1927). Ross and Anderson (1990) found nests an average of 18.4 m from shrubs

There is some evidence that Blanding's turtles are faithful to nesting sites. Petokas (1986) found that some females who nested more than once during his five-year study returned to the same nest. Congdon et al. (1983) also observed nest fidelity. Eight of 11 females in Michigan returned to a specific nesting area. and 36.3 m from trees.

Further information on habitat in specific areas follows.

Prairie marsh or wet prairie, especially associated with sandy soils, is the preferred habitat in the western part of the range, (Kofron and Schreiber 1985, Nyboer 1992). In the Nebraska sandhills, Blanding's turtles, particularly juveniles, were significantly more numerous in marshes and small ponds than in lakes and open waters (Bury and Germano 2003).

In Wisconsin, ponds were used more often than the marshes that were available (Ross and Anderson 1990); the authors surmised that the use of ponds and ditches might be due to their use as travel routes between feeding or activity centers; use of ponds with sand substrate and no aquatic vegetation was minimal. Wetlands in which the cattails had been cleared in some areas were used by the turtles but not those with dense cattail mats, indicating that availability of open water affects wetland use. Marsh habitat use was highest in early summer. Higher water quality encourages increases in invertebrate prey populations, and those habitats in Wisconsin with higher dissolved oxygen (>5.0 ppm) had greater use.

In the Massachusetts Great Meadows National Refuge near Concord, Massachusetts, Graham and Doyle (1977) found more turtles in a pool with greater amounts of decaying vegetation and algal growth than in an otherwise comparable pool. Dominant submerged aquatics there were coontail (Ceratophyllum demersum), waterweed (Anacharis occidentalis) and pondweed (Potamogeton sp.) (1977). Kofron and Schreiber (1985) also found that this turtle seemed to be dependent on waters with aquatic vegetation. In Illinois, turtles moved from less vegetated ponds that they inhabited in May and June to more highly vegetated ponds and adjacent open marshes in July (Rowe and Moll 1991) perhaps due to increased competition during times of high feeding rates.

In Minnesota, the preferred habitat is calm, shallow water with rich aquatic vegetation. The turtles are found in marsh areas in large river floodplains in the state where there also occurs sandy upland areas for nesting (Coffin and Pfannmuller 1988). See J. Herpetol. 26:233-234 for information on habitat selection by juveniles in Minnesota. In Michigan, the turtles use shallow weedy bodies of water such as permanent ponds or open marshes (Harding 1992). In Ohio, the turtles have been reported uncommon in deeper or more exposed parts of lakes but frequently found in protected coves (Carr 1952). A population in Nova Scotia is located within the central marshy area of a peninsula projecting into a lake. At this site the turtles at least formerly were abundant (Bleakney 1963). In Nova Scotia, distribution parallels that of dark acidic waters and peaty soils; in summer, often near the outflow of streams into lakes (Power et al. 1994). Sphagnum appears to be the primary indicator of juvenile and subadult habitat (McMaster and Herman 2000). Hatchlings do not seek open water upon emergence from the nest (McNeil et al. 2000).

Turtles on the northern edge of Lake Erie in Ontario also were reported as very common in a similar peninsular habitat where they were rarely seen in the open water of Lake Erie but were common on the marshy banks of the ridges that line a 20-mile-long sandspit (Adams and Clarke 1958). On Grenadier Island of the Thousand Islands region of the upper St. Lawrence River in Ontario, Canada, the turtles inhabit a 70-ha, continually flooded sedge meadow in the center of the island (Petokas 1986). Although Cook (1984) stated the turtles are often found in boggy areas in Canada, they do not inhabit bogs in Wisconsin (Vogt 1981). Perhaps Cook was referring to marshy areas as "boggy" nor are there other specific references to a bog habitat.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Females may move up to at least a few kilometers between nesting and non-nesting habitats.

Blanding's turtles are omnivores. Their favorite food items are crustaceans but they also feed on insects, leeches, snails, small fish, frogs, and occasionally some plants. Food is captured with a rapid thrust of this turtle's long neck, similar to the feeding actions of the snapping turtle (Chelydra). Feeding mostly occurs underwater and food seized on land is generally carried to the water for swallowing. Prey is either swallowed whole or if it is too large it is held by the jaws and shredded into smaller pieces by the front claws.

Comments: Unlike most aquatic turtles, Blanding's turtles will eat food both in the water and out of the water (Pope 1939, Vogt 1981). Diet quality may be the most important factor influencing growth. There is evidence that turtles from eutrophic environments grow faster and achieve larger maximum size on a carnivorous diet than do turtles on an herbivorous diet. Size differences between Michigan and Massachusetts populations have been explained by differences in food quality and availability, which affect growth rates (Graham and Doyle 1977).

Blanding's turtles have been observed consuming pondweed seeds (Potamogeton sp.), golden shiners (Notemigonus crysoleucas), and brown bullheads (Ictalurus nebulosus) where high nutrient levels from sewage effluent have stimulated the growth of high protein foods in Massachusetts (Graham and Doyle 1977). The turtles are omnivorous (Graham and Doyle 1977) and may take advantage of abundant sources of high nutrient foods when available.

Ninety-two Emydoidea examined by Penn (1950) ate a diet containing 58% crayfish by volume. Crayfish and other crustaceans comprise about 50% of the diet, insects 25%, and other invertebrates and vegetable matter 25% for turtles in New England (DeGraaf and Rudis 1983) and Michigan (Lagler 1943). Missouri turtles are primarily carnivorous, specializing in crayfish, followed by insects. They eat fishes, fish eggs, and frogs as well, with small amounts of duckweed and algae always in association with animal food (Kofron and Schreiber 1985). In Nova Scotia where crayfish are absent, the turtles eat dragonfly nymphs, aquatic beetles, and other aquatic insects as well as snails and some fish (Bleakney 1963). Researchers found that Nova Scotian hatchlings in captivity reacted strongly to the presence of live fish in their tank (Bleakney 1963). Eats mainly snails, crayfish, earthworms, insects, and plant material in Illinois (Rowe, 1992, J. Herpetol. 26:111-114).

Turtle eggs and hatchlings have a variety of predators to which they have virtually no defenses. Raccoons, skunks, and foxes are the major predators on the eggs, but they also prey upon the hatchlings and juveniles. Other predators to the young include large fish, frogs, snakes, wading birds, and crows. Adult turtles depend on their shells for protection on land and in the water rely on their strong swimming abilities to either escape to deeper waters or conceal themselves on the bottom. Rarely will the Blanding's turtle bite as a defense. It is an extremely gentle organism that can rarely be induced to bite.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: Probably there are at least a few hundred occurrences. About 170 occurrences (since 1970) were reported from six states in 1993 questionnaire to all heritage programs in the species' range.

10,000 - 1,000,000 individuals

Comments: Information on population size is generally unavailable. Most occurrences are represented by observations of single individuals. If populations averaged 50 individuals, the above minimal estimate of 300 occurrences range wide would include 15,000 individuals. However, on the west side of Weaver Dunes, Minnesota, population size was estimated at 2,500-4,600 individuals; this estimate does not include the entire population, which may be the largest existing population of this species (Pappas et al. 2000). Despite a substantial range in Minnesota, large populations are known from only a few locations (Oldfield and Moriarty 1994). In Illinois, relatively common in appropriate habitat from the Illinois River northward; rare farther south (Phillips et al. 1999).

Age class structure of Emydoidea populations often appears to be highly skewed toward adults. It has been suggested that trapping techniques and locations may be missing the juveniles that do not share the same habitat as the adults. However, in Nova Scotia, juveniles, subadults, and adults shared the same macrohabitat (McNeil et al. 2000). Possibly juveniles are more secretive (Congdon et al. 1993) or truly scarce due to nest failure (Congdon et al. 1983). In Nebraska, Germano et al. (2000) trapped many juveniles but few small individuals less than 10 cm CL.

Sex ratios are usually considered 1:1. Gibbons (1968) reported an "apparent" abundance of females though admitted that all turtles over 90 mm not identified as male by plastron shape were considered females. Most authors now consider these turtles immature under 180-190 mm.

Populations incurred extensive nest predation by carnivores in Michigan and Wisconsin (Congdon et al. 1983, Ross and Anderson 1990). Raccoons were important egg predators in Nova Scotia (see Herman et al. 1995). Standing et al. (2000) documented predation on neonates by ants, short-tailed shrews, and possibly raccoons in Nova Scotia. In Michigan, characterized by low recruitment due to high level of nest loss from predation and low nesting frequency; egg survivorship to hatching was 0.18 (Congdon et al. 1983); subsequent study revealed variable annual nest survival rate (0-63%), with annual adult survivorship exceeding 93%; demographic analysis indicated that population stability was most sensitive to changes in adult or juvenile survival and less sensitive to changes in age of sexual maturity, nest survival, or fecundity (Congdon et al. 1993, 2000). In Nova Scotia, Herman et al. (1995) and Standing et al. (2000) also found low egg and hatchling survival and noted the importance of high survivorship of adults to population stability. Annual egg failure in Nova Scotia ranged from 26.5-94 percent; in the absence of predation (nests were protected in exclosures), low incubation temperatures and nest flooding appeared to be the major causes of egg failure (Standing et al. 1999). Flooding may be a significant cause of nest failure in some areas in some years (Herman et al. 1995).

Ross and Anderson (1990) defined activity centers as the area within a habitat used by turtles for at least five days. In their Wisconsin study, activity centers were well defined and separated by long distances. Size of activity centers for both males and females were about 0.7 ha (range 0.27-0.94 ha). Activity centers of females overlapped with those of other females (average overlap: 26%) and juveniles (7.4%) as well as males (12%). Male activity centers did not overlap with those of other males. In northeastern Illinois, activity centers, defined as the distribution of a plot of radiolocations throughout the season, were not significantly different between males and females. For all turtles, activity centers ranged from 0.1 to 1.2 ha. (mean = 0.6) (Rowe and Moll 1991).

Distance between an individual's activity centers did not significantly differ between males and females in Wisconsin (Ross and Anderson 1990). Length of such movement for two males was 260 m and 635 m, respectively. For six females the mean distance moved between activity centers was 489 m. Distance between activity centers was no higher than 100 m in Illinois, and sometimes activity centers overlapped (Rowe and Moll 1987). Home range/movement was less than 100 m for individuals in Michigan (Gibbons 1968). Home range size was 1.7-22 ha in Illinois (Rowe and Moll 1987). In Minnesota, home range size averaged 7.8 ha in adults, 5.9 ha in juveniles (Piepgras and Lang 2000). In Nova Scotia, total range and movements increased with age and correlated positively with the amount of suitable habitat in an area (McMaster and Herman 2000).

Daily movements however, differed significantly between females (mean: 95.1 m) and males (mean: 48.4 m) in Wisconsin, probably due to reproductive activities of the females (Ross and Anderson 1990). In Illinois, distance of daily movements by males (mean: 48.9 m) was in agreement with that found in Wisconsin, but females did not move as far (mean: 32.4 m) because Rowe and Moll did not include movements associated with reproductive activity. Females in Illinois moved farther in May than in August, probably due to greater resource needs during reproductive periods.

In Nova Scotia, sometimes moved 5-11.5 km overland to establish residency in a different drainage (Power et al. 1994, Herman et al. 1995

Other than movement by females to locate nesting sites, Blanding's turtles exhibit three other types of terrestrial movement, as noted by Rowe and Moll (1991). During reproductively active periods, males may move long distances overland to locate mates. Secondly, short overland excursions to other water bodies are common and probably indicate explorations for improved ecological conditions or in response to social interactions. Thirdly, turtles have been observed to "estivate" on land for several hours to several days in both Illinois and Wisconsin. Ross and Anderson (1990) recorded this behavior for Wisconsin turtles in July and August during periods of cool water temperatures. Rowe and Moll (1991) observed turtles with the anterior portion of the carapace nestled in leaf litter early in the season. They suggested the Illinois turtles were also avoiding cold water temperatures and practicing thermoregulation, but the behavior might better be referred to as basking, since the turtles were quite alert.

Reported density ranges from about 6/ha (Graham and Doyle 1977) to 55/ha (Kofron and Schreiber 1985).

Comments: Generally inactive during cold winter months in north. Primarily diurnal.

In Massachusetts (Graham 1979), daily activity is bimodal during warmer weather and unimodal when the temperature drops. At 25 C the turtles have a short activity period from 5:00 to 6:00 AM EST, then rest until noon with a larger period of afternoon activity lasting until approximately 5:00 PM EST. When the temperature falls to 15 C the turtles show a continuous 8:00 to 5:00 "workday". However, the amount of total movement, movement per hour, and diet activity is greater at 25 C than 15 C, probably due to metabolism changes associated with changes in body temperature (Graham 1979).

In Illinois (Rowe and Moll 1991), peak activity was observed in the turtles during the morning in May, but afternoon activities increased during June and July. Rowe and Moll believed the low afternoon activity in May is due either to diminishing returns in resource acquisition during that time or may be explained by the turtles being engaged in basking for thermoregulation. Most likely both factors were operative. Basking on muskrat houses, steep banks of dikes and ditches, stumps, logs and driftwood is common. Basking is reported at water temperatures of 18-27 C and air temperatures of 15-27 C in Illinois. In general, males in Illinois tend to be more active than females in the afternoon and evening each day (Rowe and Moll 1991).

In Missouri (Kofron and Schreiber 1985), turtles spent 4.5 months feeding. The first feeding period was early April until mid-July and the second period of feeding extended from mid-August to mid-September. The turtles began feeding in April when water temperatures were at 18 C but ceased to feed if the temperatures dropped to 9 C. In August, the turtles resumed feeding when the water temperatures dropped to 21 C but ceased when water temperatures in September reached 17 C. Rowe and Moll (1991) also found a drop in feeding activity during June which they hypothesized was due to decreased resource availability, elevated water temperatures, or both. However, this information was derived from trapping data. Turtles wearing radio transmitters continued to be quite active during this period and actually moved away from the trapping area. Perhaps the turtles were still actively feeding in ponds elsewhere with abundant aquatic vegetation.

Individuals in Missouri entered hibernation when water temperatures were 6.2-7.5 C. At these temperatures the turtles frequently changed locations, moving as much as 13 m, but at water temperatures of 2-3 C the turtles moved only 1-2 m (Kofron and Schreiber, 1985).

In Illinois, active from about 0530 h until 2230 h; emerges from dormancy by late March, active through October or November (Rowe and Moll 1991).

Water temperatures ranging from 10-13 C, probably in addition to changes in photoperiod, food supply, and rainfall, stimulate turtle hibernation in Wisconsin between September 20 and October 22 (Ross and Anderson, 1990).

In the South, turtles may be active all year. Turtles in Missouri and Illinois have been observed moving below the ice of a frozen marsh or pond. Emergence has been reported to occur in January in Ohio (Carr 1952).

In Massachusetts, active dispersal of hatchlings from nests to wetlands occurred primarily in early to mid-morning and in late afternoon (Butler and Graham 1995).

Average lifespan

Status: captivity: 12.8 years.

Maximum longevity: 77 years (wild) Observations: Field studies have failed to find increases in mortality rates or reproductive output with age. Although it was observed an increase in embryo mortality in nests of older females, this is considered a species with negligible senescence (Congdon et al. 2001).

Mating activities begin when a courting male approaches a female, quickly mounts her carapace, and clasps its edges with his claws. To keep the female withdrawn, the male either bites at her head and forelimbs or presses down on her snout with his chin. The male may also swing his head back and forth or up and down over the female's head or blow a stream of bubbles across the top of her head. The pair will either sink to the lake bottom, float near the surface, or hang on to vegetation until fertilization is complete.

Blanding's turtles reproduce through internal fertilization with copulation taking place in the water. Mating can occur between April and November but is most concentrated in April and May. Less than half of the adult female population will reproduce in a give year. Mostly in June, females may travel considerable distances from the water to find suitable nest sites to lay their eggs. They prefer open, sunny spots in well-drained but moist sandy soil, but when lacking preferred areas, lawns, gardens, or gravel road edges will be used. Females dig a nest cavity approximately 17 cm deep and 7 to 10 cm in diameter at the mouth using alternating movements of the hind feet. They lay 6 to 21 flexible, elliptical shaped eggs measuring about 3.6 cm long. Most hatchlings will emerge 50 to 75 days later, depending on the temperature and moisture in the nest, in August or early September. Because Blanding's turtles have temperature-dependent sex determination, eggs incubated below 25 degrees C produce nearly all males and those incubated above 30 degrees C are nearly all females. The nest must first remain free of any predator attacks and then hatchlings must often travel a considerable distance to reach suitable aquatic habitat. Since few young are ever encountered in the wild, it is presumed that the hatchlings are extremely unlikely to survive the initial weeks away from the nest. These long-lived turtles will reach sexual maturity in 14 to 20 years and reproduce for approximately the next 40 years. Although Blanding's turtles generally reach 60 years of age some individuals may live to be up to a century old.

Average number of offspring: 8.

Average age at sexual or reproductive maturity (male)

Sex: male: 4380 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 6500 days.

Copulation occurs primarily March-May. Nesting occurs mid-June to mid-July in Nebraska, during 2-3 week period in June in Massachusetts, late May and June in northeastern Illinois, mid-May to early July in Michigan (Congdon et al. 2000), late May-June in Minnesota (Pappas et al. 2000), mid-June to early July in Wisconsin, mid-June in Maine (Joyal et al. 2000), mid-June to early July in Nova Scotia (Standing et al. 1999). Lays eggs in early evening (in Massachusetts, typically begins nesting when light, continues into darkness).

Nesting may vary annually by as much as 2 weeks in the same area. Nesting activity in Ontario does not commence until daily maximum temperatures reach at least 19.5 C and daily average temperature is 21.4 C (Petokas 1986). The nesting season lasts 2-3 weeks. Nesting generally occurs in the evening, beginning when it is still light but rarely completed until after dark; average time from first digging to leaving the nest by the female is 2.5 hours (Congdon et al. 1983, Linck et al. 1988). Turtles in southeastern Ontario averaged slightly less than 2 hours to complete nesting though began about the same time as those in Michigan (Petokas 1986).

Clutch size 3-22; average 15 in Nebraska, 10 in Minnesota (Pappas et al. 2000), 8-9 in Maine (Joyal et al. 2000), 8 in Ontario, 10-11 in Nova Scotia (Standing et al. 1999, 2000). DePari et al. (1987) found clutch sizes ranging from 9 to 16 eggs (mean = 12.9) for Massachusetts females whose size ranged from 200 to 220 mm. Mature females in southwestern Michigan have been measured at 160-162 mm (mean = 184.5). These turtles produced an average clutch size of 10 (Congdon, et al. 1983). Individual females lay one clutch per season in Michigan and Nova Scotia. Females may retain a single oviductal egg that is released post-nesting (Petokas 1986). Adult females may not nest in some years (68 percent nested less than annually in Nova Scotia, Standing et al. 1999).

Gutzke and Packard (1987) studied the clutches of 6 gravid females removed to the laboratory from the Valentine National Wildlife Refuge in Nebraska. The following information on the response of eggs to temperature is illuminating. At 31.0 C, 77.3% of the eggs hatched, required approximately 49 days to develop, and 100% of the hatchlings were females. At 26.5 C 95.2% of the eggs hatched, required 13-14 additional days of development, and all of the hatchlings were males.In contrast to the eggs of painted turtles of which a significant number will hatch at temperatures as low as 22 C, none of the eggs in this study hatched at 22 C. These incubation periods are in line with those reported by Ewert (1979): 30-32 C, 47.4 days; 29.5-30 C, 49.3 days; 27.4 C, 52.4 days; 25-25.5 C, 71.3 days; 24 C, 81.6 days. These relatively short incubation periods are a selective advantage for a species nesting on ephemeral or unstable substrates such as sandbars and beaches.

Hatchlings emerge in 10-17 weeks; mid-August to early October in Michigan, mid-August to late September in Minnesota (Pappas et al. 2000), late August to early October in Maine (Joyal et al. 2000). A mid- to late October emergence was observed in Minnesota (Moriarty and Linck 1995, Herpetological Review 26:99). Average time from egg laying to emergence in Nova Scotia was timed at 88 days (Bleakney 1963).

Hatchlings may emerge from the nest synchronously or asynchronously over several days. Nine of 14 nests in Michigan hatched over several days and three of these were preyed upon after emergence of the first hatchling (Congdon et al. 1983). Average time from egg laying to hatching was 84 days. There is some evidence that hatchlings may overwinter on rare occasions with emergence in the spring (Congdon et al. 1983). In Massachusetts, hatchling moved from nests to wetlands in from less than 12 hours to 9 days (Butler and Graham 1995).

Hatchlings emerge from the egg at less than 37 mm carapace length (Ewers 1979) and grow about 12 mm per year (Moriarty 1988). This rate is slowed significantly at maturity but there are few studies of growth rate in this species. Graham and Doyle (1977) found that growth rate dropped at age class 13-15 in Massachusetts turtles. This corresponded with the size of adults at sexual maturity (1977). Diet quality affects growth rate so that size at a given age is highly variable.

The age of sexual maturity of females is 14-20 years, though maturity seems to be more tied to size than to age; very long-lived, not uncommonly lives several decades (Congdon et al. 1983, Moriarty 1988, Congdon and van Loben Sels 1991; Herp. Rev. 20:53; Herman et al. 1995; Pappas et al. 2000). Kofron and Schreiber (1985) in Missouri found that males were sexually mature at 174-208 mm. Graham and Doyle (1979) believed that individuals with a carapace length less than 190 mm were immature. Male maturity may not be achieved until the 12th growing season when plastron lengths range from 181 to 190 mm in Massachusetts populations (Graham and Doyle 1977).

Recaptured turtles in Michigan have been aged at 42 years (Congdon et al. 1983) and in Massachusetts at 30-40 years (Graham and Doyle 1977). Gibbons reported in 1987 that the oldest known Blanding's turtle was 48 years old. However, Brecke and Moriarty (1989) reported a turtle in Chisago County, Minnesota, to be a minimum of 77 years old. The turtle was marked in 1926 presumably as an adult of at least 14 years. In spite of advanced age, the turtle broke no size records but was still large at 217 mm. The longevity of Blanding's turtles is a life history characteristic of the K-strategist. Combined with delayed maturity, single clutches, and a short annual reproductive period, this species is banking on many productive years by adults in a population. According to Congdon et al. (1983) 23-48% of the females in a population reproduce in a given year, and adults, barring death on the highway, can look forward to at least 15 years of reproductive activity. In this way, populations can be maintained through sufficient reproduction effort and an occasional good year in spite of long periods of low recruitment due to nest failure, predation, or hatchling mortality (Petokas 1986).

Emydoidea exhibits temperature-dependent sexual differentiation (TSD) that may actually favor males if nesting habitats become cooler due to shading.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Species: 1
Species With Barcodes: 1

Year Assessed

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Future survival of Blanding's turtle populations mainly depends on the condition and availability of wetland habitats. This species has been given legal protection in certain states. In the lower Great Lakes basin, however, they appear to be maintaining populations. As with many other species that must migrate to suitable nesting locations, fragmentation caused by roads results in the death of many turtles every year. Because this species is slow-maturing, juvenile as well as adult survivorship must remain high to ensure this species' survival (Harding 1990, 1997). Blanding's turtles are considered lower risk by the IUCN and they are a species of special concern in Michigan.

US Federal List: no special status

CITES: no special status

State of Michigan List: special concern

IUCN Red List of Threatened Species: lower risk - near threatened

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Fairly extensive range is centered in the Great Lakes region; distribution is generally spotty, with some widely disjunct populations; believed to be declining in many areas, but current status is poorly documented; major threats appear to be habitat loss and extensive egg predation.

Intrinsic Vulnerability: Highly to moderately vulnerable.

Environmental Specificity: Narrow. Specialist or community with key requirements common.

IUCN 2007 Red List: Near Threatened (LR/nt) (assessed 1996, needs updating); CITES: Not Listed; US ESA: Category 2 (Candidate for Listing); Canada Species at Risk Act: Endangered (Nova Scotia), Threatened (Great Lakes / St. Lawrence).

Population

Population Trend

Global Short Term Trend: Relatively stable to decline of 30%

Comments: Believed to be declining in many areas, though actual survey data are scant. Great Lakes area is the stronghold for the species; generally declining at the range periphery (Harding 1997). Range probably was more extensive on the central prairies of Illinois, Iowa, and Kansas before the extensive wet prairie marshes were drained. Juveniles seldom are observed (Carr 1952, Gibbons 1968, Kofron and Schreiber 1985, Fogel 1992, Hay 1992). Sampling of a population at Goose Pond in Missouri by Kofron and Schreiber revealed many adults and subadults, but only a few juveniles and no hatchlings (1985). Apparent senescence of the populations has been observed in Illinois (Fogel 1992) and Wisconsin (Hay 1992) as well. Populations declined in northwestern Indiana between the 1930s and 1990s (Brodman et al. 2002). Gibbons (1968) found only 1 individual below 90 mm in two years of capturing turtles. However, there are many questions yet to be answered about the life history of the species, and it is uncertain whether these observations are a trend or status quo. Reports on Blanding's turtle from the period prior to the 1950s caused Carr (1952) to state: "Young Blanding's turtles are astonishingly rare." Perhaps recruitment is periodic. Cyclic flushes of juveniles may have been historically the result of cyclic predation due to environmental conditions inhibiting nest detection, decreased presence of predators, or population explosions of alternate prey during some years. In some areas turtle population sizes may have been very low historically because of little naturally disturbed habitat for nesting sites. Densities may have always been high near sandy shores of large rivers or lakes. Habitat manipulation by humans has created more nesting habitat and populations may actually be higher in some areas than would have been possible presettlement due to the current abundance of quality nesting sites (Petokas 1986).

Global Long Term Trend: Decline of 30-50%

Major Threats

Degree of Threat: B : Moderately threatened throughout its range, communities provide natural resources that when exploited alter the composition and structure of the community over the long-term, but are apparently recoverable

Comments: Sensitive to habitat alteration (such as cultivation to the edge of the water of sloughs and ponds) and use of herbicides, which destroy aquatic vegetation and may affect the turtle itself (Kofron and Schreiber 1985). Inundation or drainage of wetland habitats for agriculture, river channelization, and water impoundment have reduced available habitat in Minnesota (Coffin and Pfannmuller 1988). Major problem in Illinois has been habitat destruction (Phillips et al. 1999). Drawdown activities to remove undesired fishes such as carp and/or vegetation in lakes were cited in both Illinois and Minnesota as detrimental to E. blandingii populations due to death from freezing when the substrate was exposed in late winter and poisoning from pesticides sprayed on the exposed lake bottom after the turtles were already moving in late spring (Nyboer 1992, Dorff 1992). Wetland drawdown in Minnesota resulted in high mortality from predation, road mortality (due to emigration), and winterkill (Hall and Cuthbert 2000); no mortality was observed at a control site. Development of upland nesting sites and habitat fragmentation near large metropolitan areas also affects populations (Dorff 1992). Blanding's turtles were nearly extirpated in Missouri due to marsh drainage and use of pesticides (Kofron and Schreiber 1985). Loss of their wet prairie habitat has depleted populations in Illinois (Nyboer 1992). Sex ratios may be affected by habitat changes. Habitat succeeding to shrubs creates a cooler incubation environment for the eggs so that hatchlings appear to be predominantly males in Iowa (Nyboer 1992). Road mortality has also been suggested as one of the greatest threats in Michigan, second to habitat destruction. The turtles' habit of wandering long distances to nest may be a limiting factor in their adaptation to humans (Harding 1992). Drawdown activities to remove undesired fish such as carp and/or vegetation in lakes have been cited as detrimental in both Illinois and Minnesota. These practices led to death from (1) freezing when the substrate was exposed in late winter and (2) poisoning by pesticides sprayed on the exposed lake bottom after the turtles were already moving in late spring (Dorff 1992, Nyboer 1992). Like other chelonians, Blanding's turtles are easily trapped and susceptible to collection for the pet trade. Collectors may earn $45 for a 15-20 cm turtle (Coffin and Pfannmuller 1988). Levell (2000) discussed commercial exploitation for the live animal trade. High level of predation on eggs is a problem in many areas. At Michigan's E.S. George Reserve (ESGR), nest survival declined from 44 percent before 1984 to 3 percent after 1984; this would be a substantial problem to the population if the reduction continued over the long term (Congdon et al., in press). In Michigan (Congdon et al.1983) found that nesting success rate of 22%. Combined with the percent success of eggs hatching, the probability of surviving to emergence was 0.18. Forty-nine of the 73 nests observed by Congdon were destroyed by predators, and 47% of the predation occurred within the first 24 hours after completion of nesting and 84% within the first 5 days after completion. Percent predation remained constant throughout the nesting season so that early nesters gained no advantage. Raccoons (Procyon lotor) and foxes (Vulpes vulpes and Urocyon cinereoargenteus) were the most common predators. Distance from water seems to have no correlation with predation (Congdon et al. 1983), but nests in open areas are more vulnerable than those located on roadsides or ditch banks, which might be considered habitat edge or predator travel lanes. Trails to and from nests and scent are major cues for nest predators. This might explain the decrease in predation observed over time after nest completion. In some cases the trails are quite obvious. Gruchow (1988) described them as appearing like light, smooth tire tracks spaced every four or five feet all the way down a plowed field in Wabasha County, Minnesota. Petokas (1986) found a variation in nest predation during his 6-year study in Ontario. The first year, 17% of the nests were destroyed by predators. During the next 4 years, the researchers moved nests and applied protective coverings. However, some nests were still damaged by raccoons that removed the covers, and striped skunks (Mephitis mephitis) that tunneled beneath the covers. In the 6th year, the nests were not moved or monitored but Petokas found evidence of potentially 100% of the season's nests destroyed. Although red foxes were common in the area, there was never any evidence of predation by them. Ross and Anderson (1990) found that all of 16 nests on their study site in Wisconsin were destroyed by predators; 75% were destroyed when first discovered and the other 4 were destroyed within 24 hours of nesting. Nine of the 16 nests were destroyed by skunks (Mephitis mephitis), the other predators were unknown although red fox, raccoons, and badgers (Taxidea taxus) occurred in the area. Ten of the nests were within 50 m of habitat edge. Although the adults are nearly invulnerable to predation in their native habitat, the eggs are very vulnerable and the young hatchlings that make it to the water are still susceptible to becoming the food of birds, mammals, and predatory fishes. In Michigan, nest failure due to egg infertility or death of embryos or hatchlings were observed in 11% of the nests (n=73) (Congdon et al. 1983). See Ecology Comments for further information on predation and egg survival. Populations in Minnesota suffer from loss of individuals killed on roads (Dorff 1992). Road mortality has also been suggested as one of the greatest threats to the species in Michigan (Harding 1992), second to habitat destruction. The turtles' habit of wandering long distances may be a limiting factor in their adaptation to humans (Harding 1992).
Generally tolerant of nondestructive intrusion, though nesting females are vulnerable to detrimental disturbance.

Conservation Actions

Restoration Potential: Continuous human intervention may be necessary to sustain populations ober the long term. The problems of reproductive failure combined with increased adult mortality rates must be addressed now, while research activities proceed.

Kiviat et al. (2000) documented the use of wetlands and upland nesting areas that were constructed in 1996-1997 to replace habitats lost to a school expansion in New York. Orhanic sediments and vegetation were salvaged and moved 200-700 m to create 1.4 ha of wetlands interspersed with sparsely vegetated upland soils. Based on studies in 1997-1998, radio-tracked turtles used the constructed wetlands and upland nesting areas, but no use was observed during winter or early spring.

Preserve Selection and Design Considerations: Little data are available on the extent of habitat needed by Emydoidea populations. For a given extent of wetland/aquatic habitat, population size perhaps is positively correlated with nesting site availability and quality. A well-designed preserve for this species must include both wetland habitat and upland nesting areas with safe routes between the two areas. In some cases, tilled fields where nests may remain undisturbed from further human activity may be secured to replace natural nesting areas that have been lost to development, water-level manipulation, fencing, woody invasion, etc. If nest fidelity is significant in this species, the specific nest sites must be ensured long-term protection.

Because Blanding's turtles wander overland between wetlands, genetic variation seems to have been maintained historically by the movement of males into new populations. Long-term well-being of a population is dependent on this migration. For this reason, populations along a river corridor or edging a large lake will be more secure than widely scattered groups, which may require human intervention to maintain genetic diversity.

Management Requirements: A combination of habitat preservation, including the nesting areas, and habitat restoration where wetlands have been converted to agricultural lands will go far to secure continued existence for this species. Nesting areas are a major limiting factor as are routes from wetlands to nesting areas. Turtle tunnels under existing roadways and sensitive routing of new and widened highways may be required to allow the animals to carry out reproductive activities. Because many current nesting areas are a product of human manipulation, management may require continued modification. Removal of woody invaders of open nesting areas is required as well.

Long-lived adults allow the time for rebuilding populations in areas where habitat can be recovered and restored. However, protection of nests from predators that have flourished in the human-manipulated environment, and perhaps in some instances removal of eggs for laboratory incubation and rearing in captivity for subsequent release, may be required to bolster populations in a way which mimics natural recruitment.

As efforts are made to maintain biodiversity within the remaining remnant natural communities, populations of predators will be encouraged as well as their prey. If a predator-prey balance is difficult to maintain within the small and perhaps, species-poor preserves where these turtles are protected, human intervention to increase nesting success may be required to ensure recruitment into the adult populations. This intervention might involve on-site protection of nests or incubation and re-release of hatchlings or juveniles. In Nova scotia, only 1 of 101 nests with screened predator exclosures incurred predation, whereas most unprotected nests were destroyed by predators (Standing et al. 2000). However, 58 percent of all eggs failed (did not hatch or emerge from the nest).

Movement of adults from other areas has low potential for effectiveness as the turtles will leave to return to their original homes (Nyboer 1992). However, packing eggs in soil of the new site so that hatchlings will imprint on the desired substrate has been used with marine turtles and may be effective with this species as well.

When water drawdowns are employed in turtle habitat, normal water levels need to be maintained adjacent to the drawdown areas so turtles will have a refuge. This arrangement is also beneficial for waterfowl. Appropriate procedures require several impoundments for various water levels and gradual drawdowns (Dorff 1992).

Maintenance of appropriate wetland conditions may require brush removal in some cases.

In New York, Cornell University, New York Department of Environmental Conservation (NYDEC), and TNC have cooperated in an experimental head-start program for hatchlings. In addition, the project included the creation of nesting habitat through vegetation clearing and protection of nest sites with wire exclosures.

Successful management and conservation requires protection of all life stages (ages), not programs that protect only nesting sites or involve head-starting (Congdon et al. 1993; see GECOLCOM).

Management Research Needs: Delayed sexual maturity and long adult lives make gathering complete demographic data difficult. Also, it has been noted that females will abandon nesting efforts if humans are detected prior to oviposition (Congdon et al. 1983, Linck et al. 1988). Long-term studies are needed to monitor populations and gather information on topics such as nest fidelity, cyclic recruitment, and overland movement. Gibbons (1968) stated that there are behavioral differences between juveniles and adults that are yet undetermined. Are these differences correlated with age or size? Is the diet of juveniles different from that of adults? Certainly location of juveniles is an important question to be answered. More information is needed on juvenile life history and ecology to determine how to monitor the juvenile population.

More information on the species' response to drought is needed, particularly in light of global warming and further movement of wetlands northward. Also, minimum population size and habitat size requirements are in need of research.

Biological Research Needs: Investigate juvenile life history and ecology and develop methods for monitoring this segment of the population. No information on minimum viable population size is available for this species.

Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed

Comments: At least 50 sites were reported to be protected as nature preserves or wildlife habitat areas in questionnaires to heritage programs (representing six states). Habitat somewhat protected under the Federal Wetlands Protection Act. In Minnesota, nature preserves protect several of the populations including the Anoka Sand Plain population where the preserve is managed by The Nature Conservancy and the state Department of Natural Resources (Gruchow 1988).

Needs: Nesting habitat and routes from wetlands to nesting areas are probably the most critical parts of the habitat that need protection. Protection planning should include maintaining natural, high quality water supply regimes to wetland habitats. Range wide conservation planning is needed to ensure that the range of variability of the species is adequately protected. Public education is needed to help protect the turtles from unlawful collecting and road kills.

Comments: Molecular data and morphological evidence indicate that the genus Clemmys (sensu McDowell 1964) is paraphyletic (see Bickham et al. 1996, Holman and Fritz 2001, Feldman and Parham 2002). Based on morphological data, Holman and Fritz (2001) split Clemmys as follows: Clemmys guttata was retained as the only member of the genus; Clemmys insculpta and C. muhlenbergii were placed in the genus Glyptemys (as first reviser, Holman and Fritz gave Glyptemys Agassiz, 1857, precedence over the simultaneously published genus Calemys Agassiz, 1857); and Clemmys marmorata was transferred to the monotypic genus Actinemys. Emys and Emydoidea were retained as genera separate from Actinemys. Crother et al. (2003) agreed that Actinemys, Emys, Emydoidea should be recognized as distinct genera.

Genetic data support the basic features of this arrangement. An analysis of emydid relationships based on molecular data (Feldman and Parham 2002) identified four well-supported clades: Terrapene; Clemmys guttata; C. insculpta and C. muhlenbergii; and Clemmys marmorata, Emys orbicularis, and Emydoidea blandingii. Feldman and Parham retained Clemmys guttata as the only member of that genus; regarded Clemmys marmorata, Emys orbicularis, and Emydoidea blandingii as congeneric (in the genus Emys, which has priority); and placed C. insculpta and C. muhlenbergii in the genus Calemys. However, Feldman and Parham were unaware that Holman and Fritz (2001) had given Glyptemys precedence over Calemys, so the correct generic name for these turtles under the arrangement of Feldman and Parham is Glyptemys. In contrast to Holman and Fritz (2001), Feldman and Parham (2002) argued that placing Clemmys marmorata in the monotypic genus Actinemys would unnecessarily obscure its phylogenetic relationships, and they recommended that marmorata be included in the genus Emys.

Iverson, Meylan, and Seidel (in Crother 2008) reviewed the foregoing studies as well as additional research and reasoned that monotypic genera do provide phylogenetic information and accepted Actinemys marmorata and Emydoidea blandingii as the scientific names for the western pond turtle and Blanding's turtle, respectively.

See also McDowell (1964), Merkle (1975), Lovich et al. (1991), and Bickham et al. (1996) for information on relationships among turtles of the genus Clemmys (sensu lato).