Near infrared spectroscopy as a rapid and inexpensive means of dietary analysis for a marine herbivore, dugong Dugong dugon

The objective of this study was to evaluate the potential of near infrared reflectance spectroscopy (NIRS) to estimate the botanical composition of seagrass mixtures in the stomach contents of dugongs more rapidly and cost-effectively than by conventional means. NIRS estimation of dietary composition is achieved by developing calibration equations that relate NIR spectra of samples to laboratory derived values for botanical composition. Once calibration equations have been developed, these characteristics can be estimated for further samples from their spectra alone. We developed calibration equations using samples from the stomachs of 26 dugongs (from a total data set of 128 dugongs) and validated them against a further set of 14 stomach samples. Nine dietary components were identified, 5 of which made up less than 5% of the total diet. Acceptable calibrations were obtained for the major components of dugong diets: seagrass rhizomes (pooled across all species) and the leaves of the seagrasses Thalassia hemprichii, Syringodium isoetifolium and Cymodocea species. We did not attain satisfactory calibrations for minor (<10%) dietary components. NIRS is a valid method for obtaining rapid information on the main components of the dugong diet. With larger calibration sets and fresh samples it should also be able to provide information on minor dietary components. NIRS is applicable to dietary studies of marine herbivores and should thus be of value to marine ecologists generally.