Climate change is a widely-hypothesized cause of decline in many wildlife species. For many species, there is a lack of the long-term data that are needed to assess population-level responses to climate change. Long-term growth chronologies may be obtained by monitoring a population for decades, but this is often not feasible. Age and growth patterns in the Eastern Box Turtle have often been roughly estimated by counting the number of growth rings on the carapace; however, counting the number of rings is inaccurate because these turtles may form two or more rings or no rings within a given year. Cross-dating techniques have been applied in tree-ring research to account for false and missing annual rings and ensures that individual tree rings are assigned to their correct year of growth. We applied cross-dating techniques to 50 Eastern Box Turtles in the South Carolina Piedmont. Here, we show that Eastern Box Turtles within the same geographical area demonstrate synchronous growth patterns that can be cross-dated to determine individual growth chronologies.
Results/Conclusions
First, we determined the characteristics distinguishing annual growth rings from sub-annual or ‘false’ rings in Eastern Box Turtles in the South Carolina Piedmont. Second, we determined the seasonal timing of annual ring formation. Finally, we demonstrated that the underlying assumptions of tree-ring cross dating also apply to box turtles, and we assigned tentative calendar years to each annual ring. Here, we show that cross-dating allows for long-term, exact-dated growth chronologies that can be obtained quickly and simultaneously from multiple populations. Survival and reproductive success are highly influenced by growth patterns, so these data are important in predicting population-level response to climate change. This method can be used to assess the response of Eastern Box Turtles to the changing climate and will provide valuable data to support their conservation.