Estimating Age of Turtles from Growth Rings: A Critical Evaluation of the Technique

Wilson, Dawn; Tracy, Christropher; Tracy, C

In this study, the authors conducted a review of 145 scientific papers where the counting of growth rings was utilized to estimate turtle age. Of the 145 papers, 44 papers representing 49 case studies presented data testing the use of growth ring counts for a population of turtles. Of the 49 case studies, 6 reported the technique reliable for aging turtles past sexual maturity; 15 reported the technique reliable for aging turtles to young adult (i.e. sexual maturity); 8 reported the technique reliable for aging juvenile turtles; 2 found the technique reliable with no age limit and 8 reported use of the technique unreliable as a method for aging turtles. The remainder of case studies presented data difficult to interpret as reliable or unreliable. Twenty-two papers addressed the pattern of growth ring deposition but only four case studies had sufficient data to indicate that a consistent number of rings were added each year. The authors state that the widespread use of the technique ultimately has led to its acceptance without rigorous testing of its validity or accuracy and conclude that aging turtles from counts of growth rings might be feasible in some types of studies for some species at some locations but only after calibrating the relationship between ring counts and age in each circumstance. The paper includes a table summarizing the papers that presented data testing the relationship between growth rings and age.

Estimating Age of Turtles from Growth Rings: A Critical Evaluation of the Technique

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