Accuracy Assessment of Skeletochronology in the Arizona Tiger Salamander (Ambystoma Tigrinum Nebulosum)
Skeletochronology is the most commonly used tool for evaluating the age of amphibians and reptiles. However, the accuracy of skeletochronology is questionable because few studies have utilized individuals of known age to calibrate their results. In this study, the accuracy of skeletochronology was assessed using individual Arizona Tiger Salamanders (Ambystoma tigrinum nebulosum) that were of known ages that varied from 2–15 years. Cross-sections of salamander toes were analyzed to compare the number of LAG (lines of arrested growth) to the actual age of known cohorts. Our results suggest that skeletochronology was an inaccurate tool for estimating age in this population of A. tigrinum nebulosum because it grossly underestimated age. The high intensity of endosteal resorption coupled with rapprochement of the most peripheral LAG may have produced these results. Our research indicates that skeletochronological studies that do not use individuals of known age for calibration may underestimate age.Abstract

(A) The relationship between estimated age and actual age of Arizona Tiger Salamanders (Ambystoma tigrinum nebulosum). The dashed line represents predicted age estimates assuming a 1∶1 correspondence between LAG and age in years. The solid line represents age determined by skeletochronology. The numbers inside circles represent the number of individuals at each point. (B) The relationship between estimated age and change in body condition of 15-year-old individuals.

Cross-section of a 15-year-old individual exhibiting five LAG, indicated by black arrows. R = endosteal resorption of LAG.
Contributor Notes
Section editor: J. M. Quattro.