Testing the Effectiveness of Stable Isotopic Analysis to Combat Illegal Turtle Trade and Hunting

The illegal turtle trade and hunting have become rampant in Hong Kong, posing a significant threat to all species due to illegal hunting to meet the insatiable demand in the pet and food markets. Trade regulations vary for wild-caught and captive turtles for some species, with it being illegal for wild-caught individuals only. As such, a major obstacle in enforcement against illegal trade is to differentiate between wild-caught and captive individuals. While various tools have been suggested for this purpose, little validation has been conducted, and successful application in enforcement has been rare. In this study, we evaluated the effectiveness of stable isotopic analysis in distinguishing between wild-caught and captive freshwater turtles. Specifically, we compared bulk isotopic signals, including δ13C, δ15N, δ34S, δ2H, and δ18O, between wild-caught and captive individuals of four native species, including Cuora trifasciata, Mauremys reevesii, Platysternon megacephalum, and Sacalia bealei, in Hong Kong. Our findings reveal that wild individuals exhibited significantly lower δ13C and δ15N isotopes, without overlapping, compared to captive individuals for all species. δ34S signals differed significantly between wild and captive individuals of Cuora trifasciata and Sacalia bealei. Our results demonstrate the usefulness of bulk isotope analysis in wildlife forensics for distinguishing between wild-caught and captive turtles. This method aids in validating the sources of turtles and contributes to halting the laundering of wild-caught turtles in the trade.