Nesting Habitat of the Softshell Turtle, Trionyx Mutica, below Lock and Dam 19, Upper Mississippi River

ABSTRACT Characteristics of the nesting habitat of Trionyx mutica were studied below Lock and Dam 19, upper Mississippi River. A1/2 km section of sandy shoreline where T. mutica had previously been found to be abundant was examined for nests. Nest construction occurred between mid June and mid July. Active nests, those containing eggs, were found in sandy soils within a narrow range of surface temperatures (36—37°C). The preferred sites were exposed to direct sunlight with little or no vegetation present. Over 90% of the active nests were found at sites with these characteristics. False nests were found in areas with much higher or lower soil surface temperatures, which indicated that turtles may select for optimum temperatures.