Coping with chemical complexity in mammal-plant interactions: near-infrared spectroscopy as a predictor of Eucalyptus foliar nutrients and of the feeding rates of folivorous marsupials

We investigated the utility of near-infrared reflectance spectroscopy (NIRS ) as a means of rapidly assaying chemical constituents of Eucalyptus leaves and of directly predicting the intake of foliage from individual trees by greater gliders (Petauroides volans) and common ringtail possums (Pseudoche irus peregrinus). The concentrations of total nitrogen, neutral detergent f iber, condensed tannins and total phenolics could be predicted accurately b y partial least squares regression models relating the near-infrared reflec tance spectra of foliage samples to analyses performed using standard labor atory procedures. Coefficients of determination (r(2)) for all four constit uents ranged between 0.88 and 0.98, and standard errors of prediction betwe en 0.80 mg g(-1) dry matter (DM) for total nitrogen and 5.14 quebracho equi valents g-1 DM for condensed tannins. Near-infrared spectral-based models o f food intake had r(2) values of 0.90 and 0.95 with a standard error of pre diction of 3.4 and 8.3 g DM kg(-0.75) day(-1) for greater gliders and commo n ringtail possums respectively. We used the predictive model of food intak e for greater gliders to examine the relationship between leaf palatability and documented food preferences of animals in the wild. Ranked differences in leaf palatability across four Eucalyptus species were consistent with d ocumented food preferences of greater gliders in the wild. We conclude that NIRS provides a powerful tool to predict foraging, behaviour of C. herbivo res where forage choices are determined by compositional attributes of food .