Survey of Turtles Nesting on the Missouri River on the South Dakota–Nebraska Border

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Fall 2014

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We conducted surveys for nesting false map turtles (Graptemys pseudogeographica), spiny softshell turtles (Apalone spinifera), and smooth softshell turtles (A. mutica) along the lower Missouri River on the South Dakota–Nebraska border in 2006 and 2007. We found 62 active nests (45 softshell species and 17 false map turtles) and 190 predated nests over two field seasons. Of the combined intact and predated nests, there were 2.7 false map turtle nests per sandbar and 4.2 softshell species nests per sandbar on the three man-made sandbars. On natural sandbars, there were 1.4 false map turtle nests per sandbar and 16.3 softshell species nests per sandbar. The nest characteristics that we measured were similar to those in populations of these turtles in other areas of the United States. We found no difference in the straight-line distance from nest to water between softshell species and false map turtles (t55 = 0.601, p = 0.552). Also, we found no difference in distance from nests to water between the species (t55 = 0.601, p = 0.552). In general, the distance to water traveled by nesting turtles was farther than that in previously studied populations, with softshell species averaging 61.3 m from water and false map turtles averaging 54.2 m from water. For all species, the slope of the shore nearest the nests on man-made sandbars was less (2.8°) than that on natural sand bars (11.0°) (t55= 3.699, p = 0.003). We found no difference in nearest distance to water from the nest between man-made and natural sandbars. The predation rate of monitored nests was 36% (all on natural sandbars). Softshell species nested exclusively in bare sandy areas while false map turtles tolerated sparse vegetation around the nest site. The constructed sandbars seemed to provide quality nesting habitat and were being used by turtles for nesting. The 2012 flood removed or reduced several man-made sandbars, increased the size of others, and created new sandbars. These new sandbars should be monitored to assess turtle nesting success. If the new sandbars provide suitable habitat, it may not be necessary to simulate a natural flooding regime or build new sandbars for a few years. If more constructed sandbars are needed, they should include large areas of open sand to provide easy access to nesting females, minimal vegetation for predator habitat, and a sufficient number of high areas to prevent turtle nests from being flooded.

Publication Title

Great Plains Research





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University of Nebraska Press