You are here:
CONVERTING ISOTOPE RATIOS TO DIET COMPOSITION - THE USE OF MIXING MODELS
Citation:
Phillips, D L. AND M. BenDavid. CONVERTING ISOTOPE RATIOS TO DIET COMPOSITION - THE USE OF MIXING MODELS. Presented at Wildlife Society annual meeting, Burlington, VT, September 6-10, 2003.
Description:
Investigations of wildlife foraging ecology with stable isotope analysis are increasing. Converting isotope values to proportions of different foods in a consumer's diet requires the use of mixing models. Simple mixing models based on mass balance equations have been used for dietary analyses for several decades. Several factors may complicate these analyses, including overlap in the isotopic composition of food sources and limitations on the number of sources that can be uniquely distinguished. Complexities of digestive physiology, such as concentration and digestibility differences among foods, consumer nutritional status, and differences in elemental routing to various tissues are additional factors to be considered. In this presentation, we first outline the basic isotopic mixing models and their assumptions. We then examine several extensions of mixing model analysis to deal with some of these complicating factors. These extensions include examination of experimental design and the uncertainty in dietary estimates, incorporation of elemental concentration differences among food sources, and increasing the number of food sources that can be examined. Compound-specific isotope analysis of essential amino and fatty acids offer promise for dealing with additional digestive physiology factors. Further development of mixing models for such data will enhance the utility of isotope analysis in wildlife studies.