Emydoidea blandingii (Holbrook, 1838)
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Basis for Listing
Although formerly more widespread in the eastern and central portion of the United States, the Blanding's turtle is now restricted to a small number of states and provinces in the Upper Midwest, New England, and southeastern Canada. Minnesota lies on the northwestern periphery of its range and the species is relatively widespread in the state. Although most populations within the state are restricted in size, there is an area of sand dunes and extensive marshes and backwaters along the Mississippi River which provides habitat for one of the largest populations of this species (Hamernick 2000; Pappas et al. 2000). The Blanding's turtle is a late maturing, long-lived species unable to recover quickly from catastrophic events that reduce the population (Congdon et al. 1993). Their relatively low mobility, high juvenile mortality rate, and low reproductive potential are also limiting factors for population growth. Loss and degradation of upland and wetland habitats, and mortality on roads are great threats to the species (Sajwaj et al. 1998). The Blanding's turtle was classified as a threatened species in Minnesota in 1984.
The Blanding's turtle averages 15-25 cm (5.9-9.8 in.) in length. Its most diagnostic characteristics are its domed upper shell (carapace) and its bright yellow chin and throat. The dark carapace typically has numerous, scattered yellow flecks. Adult males have a slightly concave lower shell (plastron) and a longer and thicker tail than females, with the vent extending beyond the rear edge of the carapace. Blanding's turtles are often referred to as semi-box turtles because their plastron is hinged across the front third. This hinge enables the turtle to pull the front edge of the plastron firmly against the carapace to provide additional protection when threatened.
Wetland complexes and adjacent sandy uplands are necessary to support viable populations of Blanding's turtles. Calm, shallow waters, including wetlands associated with rivers and streams, with rich, aquatic vegetation are especially preferred. In Minnesota, this species appears fairly adaptable, utilizing a wide variety of wetland types and riverine habitats in different regions of the state. In central Minnesota, shrub wetlands are utilized throughout the summer and also serve as over-wintering sites (Piepgras and Lang 2000). In southeastern Minnesota, open marshes and bottomland wetlands provide summer and winter habitat. Ephemeral wetlands are utilized in spring and early summer, while deeper marshes and backwater pools are utilized in both the summer and winter (Hamernick 2000; Pappas et al. 2000). In southwestern Minnesota, meandering streams and rivers, fens, prairie marshes, backwaters, and oxbows are important aquatic habitats, and upland habitats include adjacent agricultural lands (Lang 2003). Female Blanding's turtles often nest in agricultural fields. This may be hazardous to both adult females and nests in the form of chemicals, disking, machinery usage, increased nest predation, and shade produced by growing crops.
Biology / Life History
Blanding's turtles typically overwinter in muddy bottoms of deep marshes, backwater pools, ponds, and streams. They emerge from overwintering sites in late March to early April. Small, temporary wetlands are frequently used by Blanding's turtles in spring and early summer, when these habitats provide basking sites and mating opportunities (Sajwaj and Lang 2000). Shallow pools provide ideal amphibian and invertebrate breeding habitat, that in-turn provide an important food source for turtles. Aquatic vegetation, macro-invertebrates, and small fish may also be eaten (Oldfield and Moriarty 1994). Blanding's turtles have delayed maturation, reaching sexual maturity at approximately 12 years of age (Ernst et al. 1994), and females lay only 1 clutch of eggs each year. Clutch size varies widely, ranging from 10-26 eggs, with older, larger females often laying larger clutch sizes (Ernst et al. 1994; M. Linck, Three Rivers Park District, pers. comm.).
Conservation / Management
Efforts to delineate, protect, and restore the habitat of this species, particularly in areas that support large turtle populations, should be continued. Most of the areas with large concentrations of Blanding's turtles include some public land. Certain management activities on these lands, such as wetland drawdowns undertaken after fall, benefit other species but may negatively impact Blanding's turtles (Hall and Cuthbert 2000). In light of this, land managers should consider impacts on Blanding's turtles when managing habitat for other species. General prescribed burning guidelines have been developed for amphibians and reptiles in the Midwest, although land managers conducting burns in areas with known rare reptile or amphibian species or high concentrations of reptiles and/or amphibians may wish to contact their Regional Nongame Wildlife Specialist for input on burn planning, including timing of burns, so as to minimize impacts on these species. The use of native species should be encouraged in all habitat restoration and revegetation projects, particularly in buffer areas along rivers and streams.
Conservation Efforts in Minnesota
In the late 1980s, the Minnesota DNR requested reports of Blanding's turtles from the public. Responses were mapped to define areas of turtle concentrations, which aided in the development of conservation priorities. The Nongame Wildlife Program subsequently delineated Priority Protection Areas for Blanding's turtles so that important areas could be incorporated into environmental review and land use planning efforts. Nongame staff are currently soliciting reports of Blanding's turtles in southern Minnesota (see flyer). Please report any sightings to the Nongame Program in New Ulm.