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Archives of The Cold Blooded NewsThe Newsletter of the Colorado Herpetological SocietyVolume 31, Number 2; February, 2004 |
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Monitors and Play Behavior .01% A Turtle hurdle: 100 years Judge, Can You Spare a Lizard Close Encounter Gator mailed to Colo. greets postal workers Chinese Water Dragon Florida Scientists Seek to Trap Giant Lizards Man-Made Form of Lizard Hormone Use Of Growth Rings For Aging Turtles Female Salamanders Punish Wayward Mates PREVIOUS ISSUES 2004 index 2003 Index 2002 Index Earlier Issues About the Cold Blooded News CHS Home Page |
Use Of Growth Rings For Aging TurtlesReprinted from the Bulletin of the Chicago Herpetological Society, Vol.38, No.8, August 2003.D. S. Wilson et al. [2003, Herpetologica 59(2):178-194] note that the technique of counting growth rings to estimate age of turtles is widespread in the scientific literature. Review arti.cles to date have provided lists of authors who have found the technique useful or not, but have failed to evaluate properly how well the technique actually works. To examine how well the published literature supports a biologically meaningful rela.tionship between age and number of growth rings, the authors surveyed 145 scientific papers that have used counts of rings on scutes to estimate age of individual turtles. Of the 145 papers surveyed, the authors of 44 papers, which comprised 49 case studies, presented data testing the use of growth ring counts for a population of turtles. Of these 49 case studies, 6 reported that the use of the technique was reliable for aging their turtle species past sexual maturity, 15 reported its use to be reliable for aging turtles to young adult (i.e., sexual matu.rity), 8 reported its use to be reliable for aging juvenile turtles, 2 found it to be reliable with no age limit given, and 8 reported its use unreliable as a method for aging their turtles. Although 22 papers addressed the pattern of growth ring deposition, only four case studies had sufficient data to indicate that a consistent number of rings was added each year. This paper illustrates how the widespread use of this technique ultimately has led to its acceptance without tests of its validity or accuracy. The authors conclude that (a) studies attempting to calibrate the relationship between growth rings and age are few, (b) a majority of the papers surveyed referenced other papers that did not themselves include a test justifying growth ring counts as an estimate of turtle age, (c) 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 for each circumstance, and (d) there is currently no justification for generalizing the use of growth rings to estimate turtle age for many species. Copyright © 1998 - 2006, Colorado Herpetological Society. All rights reserved. | ||
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