Differentiation of population age groups of captive alpine musk deer (Moschus chrysogaster) based on the visible-near infrared reflectance spectra of their feces
Abstract:A new method was developed to analyze the population age groups of the captive Alpine musk deer (Moschus chrysogaster) based on the visible-near infrared reflectance spectra of their feces. A total of 145 feces samples including 50, 50 and 45 from fawns, subadults and adults, respectively, were collected at Xinglongshan Musk Deer Farm, Gansu Province. The spectral scanning on the samples was carried out in a darkroom (18-22℃, 22%-25% humidity and a special halogen lamp as the sole light source) with an ASD FieldSpec3 spectrometer. The spectral data were assigned randomly to two sets for calibration (100 data) and validation (45 data) each. The data were pretreated by the methods of S. Golay smoothing and the first derivative. The pretreated spectra were analyzed by principal component analysis (PCA), and the resultant top 6 principal components, which accounted for 95.00% of the variation among original spectral data, were used as the inputs for modeling. Individual calibration models were developed for differentiation of the population age groups of Alpine musk deer by Fisher linear discriminant (FLD), Bayes stepwise discriminant (BSD) or Back-propagation artificial neural network (BP-ANN). The predicted outcomes from the validation models of the 45 sample spectral data indicated that the accuracy rates of prediction were 84.44%, 82.22% and 80.00% for BP-ANN, BSD and FLD, respectively. The highest differentiation accuracy of 93.33% was achieved in the fawns among the three age groups. The differences in the fecal spectra among the three age groups revealed the component diversity of the feces, which corresponded with the ontogenetic development of the digestive system of Alpine musk deer. The fecal samples of subadults were of transitional attributes, but those of fawns or adults were readily differentiated by the models. The results suggested that visible-near infrared reflectance spectra of feces was a rapid and non-invasive method for distinguishing the population age groups of Alpine musk deer, and the PCA combined with BP-ANN was a preferred method.