Predicting seasonal and spatial variations in diet quality of Pyrenean chamois (Rupicapra pyrenaica pyrenaica) using near infrared reflectance spectroscopy

Monitoring nutritional status of wildlife is key to understanding the population response to changes in food availability. Several direct and indirect methods have been proposed for such purposes, but faecal nitrogen (FN) is by far the most commonly used indirect non-invasive indicator of free-ranging ruminant diet quality. In this work, two methods were used to estimate the FN content in 291 pellet samples of Pyrenean chamois (Rupicapra pyrenaica pyrenaica) collected during a 2-year period (May 2009 to May 2011) in two chamois populations from the Catalan Pyrenees, Spain: the Dumas LECO analyzer and near-infrared reflectance spectroscopy (NIRS). In order to optimize further FN estimations we performed three different NIRS calibrations: (1) general, across year, season and populations; (2) population-specific; and (3) season-specific, i.e., different periods of vegetation growth. FN ranged from 1.66 % to 2.85 % (dry matter basis) and was higher in the main vegetation growing season than in winter. Concerning NIRS calibration, our study confirmed that FN of Pyrenean chamois can be accurately determined by NIRS, since the general calibration was accurate enough to predict FN. It is concluded that NIRS represents a non-destructive, emission-free and low-cost analytical technique which may reduce the use of conventional laborious methods for estimating FN in long-term wildlife monitoring.