- (Holbrook, 1838)
Emys blandingii (Holbrook, 1838)
Taxonomic Status: Accepted
Related ITIS Name(s):
Emydoidea blandingii (Holbrook, 1838) (TSN 173789)
French Common Names: tortue mouchetée
Unique Identifier: ELEMENT_GLOBAL.2.100408
Element Code: ARAAD04010
Informal Taxonomy: Animals, Vertebrates
Genus Size: A - Monotypic genus
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Concept Reference: King, F. W., and R. L. Burke, editors. 1989. Crocodilian, tuatara, and turtle species of the world: a taxonomic and geographic reference. Association of Systematics Collections, Washington, D.C. 216 pp.
Concept Reference Code: B89KIN01NAUS
Name Used in Concept Reference: Emydoidea blandingii
Taxonomic 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).
Global Status: G4
Global Status Last Reviewed: 27Apr2005
Global Status Last Changed: 12Sep2001
Rounded Global Status: 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.
Nation: United States
National Status: N4
National Status: N3
U.S. & Canada State/Province Status
Illinois (S3), Indiana (S2), Iowa (S3), Maine (S2), Massachusetts (S2), Michigan (S3), Minnesota (S2), Missouri (S1), Nebraska (S4), New Hampshire (S1), New York (S2S3), Ohio (S2), Pennsylvania (S1), South Dakota (S1), Wisconsin (S3S4)
Nova Scotia (S1), Ontario (S3), Quebec (S1)
Implied Status under the Committee on the Status of Endangered Wildlife in Canada (COSEWIC):PS
Comments on COSEWIC: The Nova Scotia population is Endangered and the Great Lakes population is Threatened.
IUCN Red List Category: EN - Endangered
NatureServe Global Conservation Status Factors
Range Extent: 200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Range Extent Comments: 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.
Area of Occupancy: Unknown 4-km2 grid cells
Area of Occupancy Comments:
Number of Occurrences: 81 to >300
Number of Occurrences 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.
Population Size: 10,000 - 1,000,000 individuals
Population Size 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).
Number of Occurrences with Good Viability/Integrity: Unknown
Overall Threat Impact: High - medium
Overall Threat Impact 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.
Short-term Trend: Decline of <30% to relatively stable
Short-term Trend 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).
Long-term Trend: Decline of 30-50%
Intrinsic Vulnerability: Highly to moderately vulnerable.
Environmental Specificity: Narrow. Specialist or community with key requirements common.
Other NatureServe Conservation Status Information
Inventory Needs: Determine current rangewide distribution, abundance, and population trends.
Protection 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.
(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.
U.S. States and Canadian Provinces
Endemism: occurs (regularly, as a native taxon) in multiple nations
U.S. & Canada State/Province Distribution
IA, IL, IN, MA, ME, MI, MN, MO, NE, NH, NY, OH, PA, SD, WI
NS, ON, QC
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted.
For information on how to obtain shapefiles of species ranges see our Species Mapping pages at www.natureserve.org/conservation-tools/data-maps-tools.
Range Map Compilers: NatureServe 2008
U.S. Distribution by County
||County Name (FIPS Code)
Black Hawk (19013),
Buena Vista (19021)*,
Cerro Gordo (19033),
Des Moines (19057),
Palo Alto (19147),
Jo Daviess (17085),
La Salle (17099)*,
Rock Island (17161)*,
De Kalb (18033),
La Porte (18091),
St. Joseph (18141),
Presque Isle (26141),
St. Clair (26147),
St. Joseph (26149),
Van Buren (26159),
Blue Earth (27013),
Crow Wing (27035),
Lac Qui Parle (27073),
Le Sueur (27079),
Mille Lacs (27095),
St. Louis (27137),
St. Charles (29183)
St. Lawrence (36089)
Eau Claire (55035),
Fond Du Lac (55039),
Green Lake (55047),
La Crosse (55063),
St. Croix (55109),
* Extirpated/possibly extirpated
U.S. Distribution by Watershed
||Watershed Name (Watershed Code)
Piscataqua-Salmon Falls (01060003)+,
Cape Cod (01090002)+,
Middle Hudson (02020006)+,
St. Louis (04010201)+,
Upper Fox (04030201)+,
Lake Winnebago (04030203)+,
Lower Fox (04030204)+,
Little Calumet-Galien (04040001)+,
St. Joseph (04050001)+,
Upper Grand (04050004)+,
Lower Grand (04050006)+,
Pere Marquette-White (04060101)+,
Lone Lake-Ocqueoc (04070003)+,
Thunder Bay (04070006)+,
Au Sable (04070007)+,
Au Gres-Rifle (04080101)+,
St. Clair (04090001)+,
St. Joseph (04100003)+,
St. Marys (04100004)+,
Upper Maumee (04100005)+,
Lower Maumee (04100009)+,
Lake Erie (04120200)+,
Oak Orchard-Twelvemile (04130001)+,
Upper St. Lawrence (04150301)+,
St. Regis (04150306)+,
Upper Wabash (05120101)+,
Middle Wabash-Little Vermilion (05120108)+,
Middle Wabash-Busseron (05120111)+,
Little Wabash (05120114)+*,
Upper White (05120201)+
Mississippi Headwaters (07010101)+,
Leech Lake (07010102)+,
Crow Wing (07010106)+,
Long Prairie (07010108)+,
Twin Cities (07010206)+,
Pomme De Terre (07020002)+,
Lac Qui Parle (07020003)+,
Middle Minnesota (07020007)+,
Blue Earth (07020009)+,
Le Sueur (07020011)+,
Lower Minnesota (07020012)+,
Upper St. Croix (07030001)+,
Lower St. Croix (07030005)+,
La Crosse-Pine (07040006)+,
Upper Chippewa (07050001)+,
Lower Chippewa (07050005)+,
Eau Claire (07050006)+,
Red Cedar (07050007)+,
Upper Iowa (07060002)+,
Grant-Little Maquoketa (07060003)+,
Upper Wisconsin (07070001)+,
Lake Dubay (07070002)+,
Castle Rock (07070003)+,
Lower Wisconsin (07070005)+,
Upper Wapsipinicon (07080102)+,
Lower Wapsipinicon (07080103)+,
South Skunk (07080105)+,
North Skunk (07080106)+,
Upper Cedar (07080201)+,
Shell Rock (07080202)+,
West Fork Cedar (07080204)+,
Middle Cedar (07080205)+,
Lower Cedar (07080206)+,
Upper Iowa (07080207)+,
Middle Iowa (07080208)+,
Lower Iowa (07080209)+,
Upper Rock (07090001)+,
Lower Rock (07090005)+,
Des Moines Headwaters (07100001)+,
Upper Des Moines (07100002)+,
East Fork Des Moines (07100003)+,
Middle Des Moines (07100004)+,
North Raccoon (07100006)+,
South Raccoon (07100007)+,
Lake Red Rock (07100008)+,
Lower Des Moines (07100009)+,
Des Plaines (07120004)+,
Upper Illinois (07120005)+,
Upper Fox (07120006)+,
Lower Fox (07120007)+,
Lower Illinois-Senachwine Lake (07130001)+,
Lower Illinois-Lake Chautauqua (07130003)+,
Lower Illinois (07130011)+*
Rainy Headwaters (09030001)+
Middle Niobrara (10150004)+,
Lower Big Sioux (10170203)+,
Middle Platte-Buffalo (10200101)+,
Lower Platte (10200202)+,
Upper Middle Loup (10210001)+,
Lower Middle Loup (10210003)+,
South Loup (10210004)+,
Upper Elkhorn (10220001)+,
North Fork Elkhorn (10220002)+,
Lower Elkhorn (10220003)+,
Little Sioux (10230003)+,
Big Papillion-Mosquito (10230006)+,
Lower Grand (10280103)+,
Upper Chariton (10280201)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Basic Description: A turtle with an adult shell length of usually about 12-18 cm.
General Description: Medium to large (125-260 mm) turtle (Ernst and Barbour 1972) with a yellow chin and throat and a long neck. The elongated, domed, smooth, blue-black carapace is neither keeled nor serrated. Each pleural and vertebral scute has tan to yellowish spots or slightly radiating lines; the marginals are heavily spotted. The bright yellow plastron has large, dark, symmetrically arranged blotches on the posterior lateral third of each scute; the blotches may hide the yellow color on older adults. A well-developed hinge lies between the pectoral and abdominal scutes. The tail and limbs are blue-gray, black, or brown with some yellow or light brown spots. The head is large and flat, black or dark brown, possibly with scattered yellow spots. The eyes protrude. The upper jaw is notched terminally and may be marked with dark bars. Hind feet are weakly webbed.
Sexual dimorphism is not pronounced. In females the tail is more slender and the cloacal opening is located anterior to the rear carapacial margin. The males have plastrons more noticeably concave (Vogt 1981, Gibbons 1968). Kofron and Schreiber (1985) in Missouri found that concavity of the plastron does not appear until the turtle has a plastron length of 174-180 mm. They considered all individuals over 180 mm plastron length with a flat plastron to be females. Detailed observations of 74 turtles by Graham and Doyle (1979) revealed that only males showed plastron erosion and pitting.
The following measurements and ratios were gathered by Graham and Doyle (1979) from their study population in Massachusetts and may be useful to further separate the sexes. The ratio of plastron length to carapace length is significantly greater in females (ratio = 1.008, n = 33) than in males (ratio = 0.956, n = 41). The mean carapace length is greater in males (mean = 15.5 mm, range 182.4233.7) than in females (mean = 204.2 mm, range 178.9-217.5), but plastron lengths are not significantly different. Maximum shell height is significantly greater for females (mean = 84.5 mm, range 70.3-94.3) than for males (mean = 80.6 mm, range 69.8-90.6) as is the ratio of shell height to carapace length (females ratio = 0.415, males ratio = 0.375). Carapace width is significantly greater in males (mean = 146.5 mm, range = 125.6-161.3) than in females (mean = 139.0 mm, range = 121.7-148.6) and the ratio of carapace width to plastron width is also greater for males (ratio = 1.307) than for females (ratio = 1.240).
The carapace of a hatchling is rounded and keeled, 28-35 mm in length, and dark brown to black or gray, usually with some light spots or dashes on the carapace though some may be patternless. Ewert (1979) reported hatchlings to be 36.5 mm carapace length and 32.1 mm plastron length (1979). The top of the head, neck, and soft parts are black with light markings on the chin and rather prominent light lines on the tail. The plastron has a large, black central blotch or is predominantly black with light yellow on the edges. The tail is proportionately much longer than in the adult, being 65 to 70 % of the carapace length or even as long as the carapace. The tail and the deeply notched jaw like the adult distinguish them from the hatchlings of other species. The hinge may not always be apparent on young ones (Conant 1951). The yellow undersurface of the neck appears at 3 years of age (Vogt 1981).
Diagnostic Characteristics: 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.
Reproduction Comments: 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.
Ecology Comments: 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).
Locally Migrant: Y
Long Distance Migrant: N
Mobility and Migration Comments: Females may move up to at least a few kilometers between nesting and non-nesting habitats.
Riverine Habitat(s): CREEK, Low gradient, MEDIUM RIVER, Pool
Lacustrine Habitat(s): Shallow water
Palustrine Habitat(s): FORESTED WETLAND, HERBACEOUS WETLAND, Riparian, SCRUB-SHRUB WETLAND
Special Habitat Factors: Benthic, Burrowing in or using soil
Habitat 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.
Adult Food Habits: Carnivore, Herbivore, Invertivore, Piscivore
Immature Food Habits: Carnivore, Herbivore, Invertivore, Piscivore
Food 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).
Adult Phenology: Diurnal, Hibernates/aestivates
Immature Phenology: Diurnal, Hibernates/aestivates
Phenology 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).
Length: 27 centimeters
Not yet assessed
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 & 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).
Monitoring Requirements: Protected populations should be monitored to determine if reproduction is successful. Trapping has been successful in monitoring the population of adults, but there is some question as to whether the juveniles are being missed by the procedure or location. Counting nests or remains thereof in a known nesting area can be useful to monitor reproductive effort. Use of volunteers to report sightings has been very successful in expanding range information.
See Butler and Graham (1993, Herpetol. Rev. 24:21-22) for information on tracking hatchlings with fluorescent pigments.
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.
Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely recurring presence, at a given location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals (including eggs) in or near appropriate habitat where the species is presumed to be established and breeding.
Mapping Guidance: Occurrences should include nesting areas, travel corridors between the wetlands and nest sites, and other upland use areas, if known, but occurrences based on captures/observations of individuals in wetlands should include only the known distribution of the population and not include large areas of upland habitat (not known to be occupied) that may extend between occupied wetlands within the appropriate separation distances.
Separation Barriers: Busy highway or highway with obstructions such that turtles rarely if ever cross successfully; untraversable topography (e.g., cliff); densely urbanized area lacking aquatic or wetland habitat.
Alternate Separation Procedure:
Separation distances are as follows: continuous riverine-riparian corridors, 10 km; mosaics of aquatic-wetland and undeveloped upland habitat, 10 km; continuous, undeveloped upland habitat lacking aquatic or wetland habitat, 5 km; upland habitat with significant but not intense development (e.g., scattered buildings in otherwise "natural" habitat), 2 km. Other separation distances may be used when adequate site-specific data indicate that these separation distances are inappropriate for a particular population. Any such deviations should be explained in the element occurrence record.
Separation Justification: Some data indicate relatively limited movements. In Wisconsin, distance between activity centers (areas used for at least five days) was 260 m and 635 m for two males and averaged 489 m for six females (Ross and Anderson 1990). Home range/movement was less than 100 m for individuals in Michigan (Gibbons 1968). Home range area 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). Home ranges in the suburban Chicago area of Illinois averaged less than 10 ha, though nesting excursions evidently were not included (Rubin et al. 2001). 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). A 22-ha home range would be about 0.5 km in maximum width if square and roughly 1 km long if twice as long as wide. This might suggest that a small separation distance may be appropriate.
However, long-distance movements are not uncommon. At the George Reserve in Michigan, some turtles traveled up to 3 km from their resident wetland (Congdon presentation at 1998 Blandingturtle workshop). In Minnesota, turtles moved up to 3.5 km (Dorff 1995). In Wisconsin, Blandingturtles moved approximately 6 km between spring and fall recaptures (Theil, pers. comm.). In Nova Scotia, where Blandingturtles are strongly associated with habitat along rivers and streams, an individual turtle moved over 3 km in less than 14 days (Herman et al. 1995). Three males moved a minimum of 5, 8.5, and 11.5 km overland to establish residency in different drainages (Power et al. 1994, Herman et al. 1995). In Maine, radio-tagged individuals moved an average of 680 m (90-2050 m) straight-line distance between different wetlands used for at least 5 days (Joyal et al. 2001). Upland dormancy sites were up to 110 m from the nearest wetland (Joyal et al. 2001). In New York, two wetland populations of Blandingturtles nearly 3.5 km apart exhibited occasional movement of individuals between the wetlands (Paul Novak, pers. comm).
These data suggest that large separation distances are appropriate for riverine-riparian corridors. Presumably, despite occasional long overland movements, upland habitat is less likely to be traversed, so separation distances across areas with upland habitat are smaller.
In Michigan (Congdon et al. 1983), turtles traveled more than 1 km from water to nest. Nests were 2-1115 m (average 135 m) from the nearest water. Most females returned to same general nesting area each year. Nesting areas usually were not immediately adjacent to female's marsh habitat. In Wisconsin, females nested usually in grassland, average of 168 m from water and average of 620 m from non-nesting activity center (Ross and Anderson 1990). In Nova Scotia, nesting sites were up to 1.4 km from water (Herman presentation at 1998 Blandingturtle workshop). In Maine, radio-tagged individuals moved an average of 633 m (100-1620 m) straight-line distance from the wetland used prior to nesting to their nesting site.
Available movement data for nesting females and for individuals moving overland between wetlands indicate that a separation distance of several kilometers for upland habitat is needed to ensure that single populations are not artifically divided into multiple occurrences.
Inferred Minimum Extent of Habitat Use (when actual extent is unknown): 1 km
Author: Hammerson, G., and C. D. Hall
U.S. Invasive Species Impact Rank (I-Rank)
Not yet assessed
NatureServe Conservation Status Factors Edition Date: 27Apr2005
NatureServe Conservation Status Factors Author: Soule, J., K. L. Thompson, B. Van Dam, and G. Hammerson
Management Information Edition Date: 30Sep1993
Management Information Edition Author: THOMPSON, K. L., B. VAN DAM, AND G. HAMMERSON
Element Ecology & Life History Edition Date: 23May2008
Element Ecology & Life History Author(s): THOMPSON, K. L., B. VAN DAM, AND G. HAMMERSON
Zoological data developed by NatureServe and its network of
natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).
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