Factors Affecting Nesting Times in the Painted Turtle Chrysemys picta in Nebraska

Abstract Although general descriptions of nesting in painted turtles (Chrysemys picta) are numerous, few studies have quantified the timing of the components of the nesting process, and no previous study has analyzed the factors influencing those times. The present study was conducted on the Crescent Lake National Wildlife Refuge in Garden County, Nebraska, in June 2012 and 2013 and focused on a single nesting population of female C. picta. We recorded times for the initiation of the nest foray, and the beginning and conclusion of nesting, and calculated search and construction times. Although highly variable, on average females left the marsh at 1709 hrs (n = 130), began nesting at 1745 hrs (n = 141), and finished nesting at 1915 hrs (n = 135). Search time averaged 26 min (n = 79) and nest construction time averaged 97 min (n = 104). We investigated the effects of female body size, air temperature, time of day, nest day, clutch number, substrate type, and reproductive output on these times. Smaller females nested earlier in the day, construction times were shorter in warmer temperatures, nests begun earlier in the day were completed more quickly, and nest times were longer earlier in the season and for first vs. second clutches. Soil type and measures of reproductive output had no effects on nesting times. These results suggest that temperature is a primary driver of nesting times, as these turtles exploit the afternoon–evening window of optimal temperatures, avoiding heat stress earlier in the afternoon and much colder evening temperatures as well as a presumed increase in predation risk after dark.