An Examination of the Accuracy of Using Plastral Scute Rings to Age Spotted Turtles (Clemmys guttata)

Abstract

Abstract The use of plastral scute rings to age turtles is a widely practiced technique, but a lack of rigorous field testing of this method has led to critiques of its usefulness and accuracy. We tested the method's effectiveness for aging spotted turtles (Clemmys guttata) by calculating an Age-Increase Ratio and by recording changes in the number of scutes within a year. We found no correlation between the change in the number of scute rings and the number of years between captures, which likely stems from the observer error associated with the difficulty of accurately counting scutes on older turtles; however, we did record a significant correlation between the number of scute rings and body size.