Weather--associated Triggers of Nesting Activity of Blanding’s Turtles (Emydoidea blandingii) in Northeastern Illinois

Environmental triggers of nesting activities in turtles are poorly known, but important for guiding species protection efforts. Blanding’s Turtle (Emydoidea blandingii) is a species of concern throughout much of its range and is thought to prefer to nest on wet warm nights. Weather conditions during the nesting season were analyzed from 2013-2017 of a Blanding’s Turtle population located within the Lake Plain of northeastern Illinois and southeastern Wisconsin to identity climate conditions most associated with nesting activity. Peak nesting dates each year were associated with warmer mean temperature in the preceding months of March, April, and May such that on warmer years the majority of turtles nested earlier. Within a given nesting season, nights in which nesting activity occurred had higher maximum (x̅=27.6 C), mean (x̅=21.9 C), and minimum temperatures (x̅=15.9 C) than nights without nesting behavior. No pattern between nesting activity and precipitation was evident. Average barometric pressure was lower on nights with nesting activity (p=0.03). When the moon was in its brightest stages (Waxing Gibbous to Last Quarter), nesting behavior was more likely (p=0.0016). Nights when nesting occurred tended to have winds from the south (p=\u3c0.001), which are generally associated with warmer temperatures and lower average air pressure in the study region. In conclusion, warmer nights with lower barometric pressure, brighter moon phase, and winds from the south appear to be drivers of nesting activity in Blanding’s Turtles. These readily measured environmental triggers provide a useful guide to biologists to increase efficiency in finding and protecting nests and nesting females