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North Freedom, WI, United States

Geller G.A.,E7503 County Highway C
Chelonian Conservation and Biology | Year: 2012

Incidental observations on nest predation dynamics at 2 map turtle (Graptemys spp.) nesting sites along the Wisconsin River, Iowa County, Wisconsin, were obtained during primary research on the use of electric fencing to decrease turtle nest predation. Sites were continuously monitored by digital trail cameras during the 2008-2011 reproductive seasons. Raccoons (Procyon lotor) displayed temporally focused turtle nest foraging efforts across both sites and years and were the only confirmed nest predators. Striped skunks (Mephitis mephitis), Virginia opossums (Didelphis virginiana), coyotes (Canis latrans), and American crows (Corvus brachyrhynchos) were less frequent on site but also displayed recurring seasonal chronologies. Nest predation levels exceeded 90%, with short nest survival timelines suggesting relatively high predation pressures on these sites. Available data provided only limited evidence that post-nest construction rainfall reduced nest predation rates. © 2012 Chelonian Research Foundation. Source


Incidental observations on the nesting ecology of Ouachita map turtles (Graptemys ouachitensis) were made at 2 sites on the Wisconsin River, Iowa County, Wisconsin, during research on the use of electric fencing to decrease turtle nest predation. Sites were continuously monitored by digital trail cameras during the 2008-2011 reproductive seasons. Turtles nested in a bimodal diel pattern overall, the result of a reduction of midday nesting activity on relatively warm days. Nesting duration was relatively short compared to most emydids and was inversely correlated with ambient air temperatures. Precipitation within 24 hrs prior to nesting was not associated with levels of nesting activity. Younger nests appeared to have greater survival during short-term flooding events than did older nests. © 2012 Chelonian Research Foundation. Source


Visible sign produced by nesting turtles has been suggested to be a cue used by foraging raccoons (Procyon lotor) to locate nests. Experiments investigating the potential for reducing turtle nest predation by eliminating these surface markings by broom sweeping nesting areas were conducted at 2 Graptemys nesting sites along the lower Wisconsin River in Iowa County, Wisconsin, during 2013 and 2014. Ninety-five percent of the natural nests in unswept control areas (n = 20) and all of the nests in swept treatment areas (n = 16) were depredated by raccoons within 24 hrs. Supplemental artificial nests with refilled manufactured cavities but lacking potential olfactory turtle- or egg-related cues were also excavated by raccoons within similar time lines (97% within 24 hrs) and at high rates both when unswept (100%, n = 20) and when swept (95%, n = 19). However, artificial facsimiles of the surface markings left by nesting turtles, lacking cavities, were disturbed less frequently (26%, n = 19). Findings suggest that broom sweeping was ineffective because the location cues used by raccoons to find newly constructed nests are not primarily visual but olfactory and related to soil profile disturbance, possibly via the microbial metabolite geosmin. © 2015 Chelonian Research Foundation. Source

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