Nest predation is an important source of mortality in turtles. We have been studying nest predation on ornate box turtles (Terrapene ornata) for several years at Hawkeye Wildlife Area, Johnson County. Iowa. In the summer of 2008, we conducted an experiment to determine what features predators use to identify turtle nests. The experiment consisted of a series of 1m x 1m square grids with an experimental nest at each corner. Replicate grids were placed at increasing distances (5, 20, or 35m) from shrub or tree cover to determine if predation increased or decreased with distance into the open prairie. This experiment was conducted simultaneously at three sites, including two where there are concentrations of turtle nests and one located in between these at which we know of no nesting. Each grid contained four treatments, which differed from one another by a single aspect of either their contents (a chicken egg or no egg), construction (we either dug a nest hole or did not disturb the soil), or marking (locations were either marked with a wire surveying flag or not). Survival analysis indicated that soil disturbed by digging a nest is the primary feature predators use to identify nests. They appear not to be able to specifically detect underground eggs, nor do they use flags as cues. Overall, nests farthest from cover experienced significantly lower predation than those closer to cover. Predation began latest at the site with no history of nesting, suggesting that predators search more where turtles regularly nest.
Pierce Sweeny, ’09 Peoria, AZ
Amanda Brodin, ’09 Parker, CO
Major: Biochemistry and Molecular Biology, History
Brock Nelson, ’11 Blue Grass, IA
Amanda Gilbert, ’10 Bettendorf, IA
Sponsors: Robert Black and S. Andrew McCollum