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The diets and environments that individuals experience can vary greatly within and among wildlife populations. These individual experiences can be compared using the chemical signatures of animal tissues, which can differentiate animals into groups, including those raised in the wild versus those held in captive facilities. In this study, we compared different combinations of four stable isotope ratios and 15 trace elements derived from the claw tips of captive wood turtles throughout the eastern U.S. and wild wood turtles (Glyptemys insculpta) from Maine to develop predictive models used to determine their origins. The purpose of this work is to develop an objective statistical tool that law enforcement can use to help prosecute poachers. We found that the chemical signatures of 14 (12 trace elements and 2 stable isotope ratios) of the 19 markers we explored were different between wild and captive wood turtles, thus reflecting the differences in their diets and environments. We found that our stable isotope ratio model had nearly perfect predictive accuracy in classifying wild wood turtles as wild and captive wood turtles as captive, whereas our trace element and combined model were 100% accurate, thus validating this statistical approach for determining the origins of confiscated wood turtles from Maine. [ABSTRACT FROM AUTHOR]

Simple Summary: Wildlife trafficking is a major contributor to global biodiversity loss, especially reptiles, which are confiscated by law enforcement more than any other vertebrate class. Wildlife forensic experts can use chemicals from animal tissues to determine the origin of confiscated animals. Such physical evidence can help law enforcement prosecute wildlife traffickers in court and hold poachers accountable. In this study, we developed a statistical tool that can be used to determine if a confiscated wood turtle (Glyptemys insculpta) from Maine came from the wild or captivity. We used carbon and nitrogen stable isotopes from wood turtle claw tips to construct a statistical model that correctly classified all wild turtles as wild and nearly all captive turtles as captive (predictive accuracy 97.2%). Results from our study can be used to assist law enforcement in Maine and to develop a forensics tool used to help combat the illegal turtle trade. 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. [ABSTRACT FROM AUTHOR]

In human-dominated landscapes throughout the world, wildlife seek out anthropogenic foods because they are high in nutritional value and are consistently available. To investigate this mode of foraging, some researchers use stable isotope analysis to detect these animals in populations and estimate their individual diets. In this study, we develop an integrative approach to measure the proportion of corn, a C4 plant, in the diets of free-ranging mammalian omnivores in C3-dominated ecosystems. We fed captive mice corn, C3 plants, and meat until carbon stable isotopes (δ 13C) from each diet equilibrated in their hair. We then used carbon discrimination factors (Δ 13C; offsets between stable isotope values of consumer tissues and their foods) for mice from these feeding trials and a simple carbon stable isotope mixing model to estimate the corn-based diets of free-ranging American black bears in Wisconsin and brown bears in Slovenia. We used Δ 13C factors for mice to estimate the diets of bears because mouse models are used commonly to study mammalian diet and health, including humans and bears, and body mass has no effect on carbon discrimination factors in monogastric mammalian omnivores. In this study, we found that mice grew fastest, largest, and δ 13C values equilibrated quickest in the hair of mice fed meat versus plant-based diets, suggesting protein quantity (quality was the same) has an effect on Δ 13C. Evidence also suggests that Δ 13C did not increase with animal growth rate as all mice grew throughout the 109-day feeding trials, but isotopic equilibration occurred early while mice still were subadults and was maintained throughout their adult lives. We also found that Δ 13C was highest and most variable in the hair, serum, and liver, of mice fed a mixed diet of C3 plants, supporting our mixed diet hypothesis that states that Δ 13C varies more among tissues of animals fed mixed diets than animals fed nonmixed diets because the former are composed of multiple foods, each with different macromolecular and isotopic compositions. Lastly, we found that corn may have been a more important component of bear diets in Wisconsin than previously thought (adults: x ¯ = 29%; x ¯ = 33%; subadults: x ¯ = 22%; x ¯ = 28%), and male brown bears may have fed on 50% more corn (⁠ x ¯ = 47% versus 31%) in autumn during a year when beechnut availability was low. In a world that is rapidly changing, it is more important than ever to develop the appropriate quantitative tools to measure the impact people have on wildlife. Here, we provide such a tool for monogastric mammalian omnivores and encourage other researchers to do the same for other taxa of interest. [ABSTRACT FROM AUTHOR]