Plastral Patterns Serve an Anti-Predator Function in Freshwater Turtle Hatchlings

Color and pattern serve as a range of anti-predator defense mechanisms across taxa, from crypsis to warning coloration, and these phenomena are well described across invertebrate and vertebrate systems. Coloration is often assumed to have a consistent anti-predator function across life stages, but research conducted at a single life stage can yield valuable insight into the ecological and evolutionary significance of coloration across shifts in stage-specific selection pressures. Painted turtles (Chrysemys picta) are so named for their striking coloration and patterning. In this study, we use simulated hatchling painted turtles to test the anti-predator function of shell coloration on land. Using resin models, we demonstrate, for the first time, that plastral patterns have an anti-predatory function in painted turtle hatchlings in conditions ecologically relevant to nest dispersal. Specifically, turtle models with simple patterns were predated significantly more than their complex-patterned counterparts. This suggests that plastral pattern may serve as an anti-predator strategy through background matching or disruptive coloration. These results provide evidence for the poorly understood functional importance of color and pattern variation in this species and demonstrate the need to test the roles of defensive coloration and patterning across life stages to better understand their ecological and evolutionary significance.