Abstract
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.
Highlights
The analysis of stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) is a widely used approach in trophic studies at various ecological scales, from individuals to entire food webs (Boecklen, 2011; Navarro et al, 2011; Newsome et al, 2007)
Our study suggests that near-infrared reflectance spectroscopy (NIRS) can provide a time-and cost-efficient method to evaluate stable isotope ratios of carbon and nitrogen when substantial differences in δ13C or δ15N are expected, such as when discriminating among different trophic levels in diet
Our results show that NIRS can be a suitable tool to estimate stable isotopes in RBC samples from a free-living animal population
Summary
The analysis of stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) is a widely used approach in trophic studies at various ecological scales, from individuals to entire food webs (Boecklen, 2011; Navarro et al, 2011; Newsome et al, 2007). The time period represented depends directly on the turnover rate of the tissue sampled and the species. It typically ranges from a few days in blood plasma, to several weeks in red blood cells, and up to several years in metabolically inert tissues such as bone collagen, teeth, or baleen (Hanson et al, 2009; Trueman et al, 2019). Near-infrared reflectance spectroscopy (NIRS) can be used as a cost-and time-effective method to measure tissue properties in animals and plants (Chodak, 2008; Cozzolino et al, 2001; Windley et al, 2013). We used blood samples previously collected in a study on a pelagic seabird, the Antarctic petrel (Thalassoica antarctica), to assess the suitability of NIRS to estimate stable isotopes in a free-living animal species. Seabird ecology often relies on stable isotope analyses to estimate seabird diet or feeding habitat (Bond et al, 2016; Hovinen et al, 2019); a time and cost-efficient method for the estimation of δ13C and δ15N would facilitate ecological research on seabirds and on more wildlife in general
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