Forensic Application of Stable Isotopes to Distinguish between Wild and Captive Turtles

John B Hopkins 3rd; Cheryl A Frederick; Derek Yorks; Erik Pollock; Matthew W H Chatfield

doi:10.3390/biology11121728

Forensic Application of Stable Isotopes to Distinguish between Wild and Captive Turtles

Biology (Basel). 2022 Nov 29;11(12):1728. doi: 10.3390/biology11121728.

Authors

John B Hopkins 3rd¹, Cheryl A Frederick¹, Derek Yorks², Erik Pollock³, Matthew W H Chatfield⁴

Affiliations

¹ Center for Wildlife Studies, 36A High St., Camden, ME 04843, USA.
² Maine Department of Inland Fisheries and Wildlife, Bangor, ME 04441, USA.
³ Stable Isotope Laboratory, University of Arkansas, Fayetteville, AR 72701, USA.
⁴ School of Biology and Ecology, University of Maine, Orono, ME 04469, USA.

Abstract

Wildlife traffickers often claim that confiscated animals were captive-bred rather than wild-caught to launder wild animals and escape prosecution. We used stable isotopes (δ¹³C and δ¹⁵N) derived from the claw tips of wild wood turtles from Maine and captive wood turtles throughout the eastern U.S. to develop a predictive model used to classify confiscated wood turtles as wild or captive. We found that the claw tips of wild and captive wood turtles (Glyptemys insculpta) were isotopically distinct. Captive turtles had significantly higher δ¹³C and δ¹⁵N values than wild turtles. Our model correctly classified all wild turtles as wild (100%) and nearly all captive turtles as captive (94%). All but two of the 71 turtles tested were successfully predicted as wild or captive (97.2% accuracy), yielding a misclassification rate of 2.8%. In addition to our model being useful to law enforcement in Maine, we aim to develop a multi-species model to assist conservation law enforcement efforts to curb illegal turtle trafficking from locations across the eastern United States and Canada.

Keywords: carbon; forensics; nitrogen; stable isotopes; wood turtles; δ13C; δ15N.

Grants and funding

This research was funded by the Maine Department of Inland Fisheries and Wildlife, the Dorr Foundation, the William P. Wharton Trust, The Lawrence E. White Family Foundation, and the USDA National Institute of Food and Agriculture, McIntire-Stennis Project Number ME0-42301 through the Maine Agricultural and Forest Experiment Station.