Using near-infrared reflectance spectroscopy (NIRS) to estimate carbon and nitrogen stable isotope composition in animal tissues.

Stable isotopes analysis (SIA) of carbon and nitrogen provides valuable information about trophic interactions and animal feeding habits.We used near-infrared reflectance spectroscopy (NIRS) and support vector machines (SVM) to develop a model for screening isotopic ratios of carbon and nitrogen (δ 13C and δ 15N) in samples from living animals. We applied this method on dried blood samples from birds previously analyzed for δ 13C and δ 15N to test whether NIRS can be applied to accurately estimate isotopic ratios.Our results show a prediction accuracy of NIRS (R 2 > 0.65, RMSEP < 0.28) for both δ 13C and δ 15N, representing a 12% of the measurement range in this study.Our study suggests that NIRS can provide a time- and cost-efficient method to evaluate stable isotope ratios of carbon and nitrogen when substantial differences in δ 13C or δ 15N are expected, such as when discriminating among different trophic levels in diet.