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

Abstract

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 (Pseudocheirus peregrinus). The concentrations of total nitrogen, neutral detergent fiber, condensed tannins and total phenolics could be predicted accurately by partial least squares regression models relating the near-infrared reflectance spectra of foliage samples to analyses performed using standard laboratory procedures. Coefficients of determination (r ) for all four constituents ranged between 0.88 and 0.98, and standard errors of prediction between 0.80 mg gdry matter (DM) for total nitrogen and 5.14 quebracho equivalents gDM for condensed tannins. Near-infrared spectral-based models of food intake had r values of 0.90 and 0.95 with a standard error of prediction of 3.4 and 8.3 g DM kg day for greater gliders and common ringtail possums respectively. We used the predictive model of food intake 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 documented food preferences of greater gliders in the wild. We conclude that NIRS provides a powerful tool to predict foraging behaviour of herbivores where forage choices are determined by compositional attributes of food.

Rapid Assessment of the Nutritional Value of Foods Eaten by Mountain Gorillas: Applying Near-Infrared Reflectance Spectroscopy to Primatology

“…Ecological studies used NIRS to predict biological response to dietary properties, such as food intake, feeding rates (McIlwee et al 2001), and tannin-binding ability (DeGabriel et al 2008). Studies in the animal science industry have developed NIRS to predict botanical composition of the diets using the spectra of feces (Glasser et al 2008;Parveen et al 2008), which could be particularly useful for determining the diet contents of elusive primates, and others have used NIRS to examine measures of digestibility (Steen et al 1998).…”

“…This offers a powerful alternative method to address better many questions of interest to primate nutritional ecologists. Researchers have widely used near-infrared spectroscopy to estimate the nutritional composition of foodstuffs in agriculture and food science since the 1970s (Norris et al 1976;Shenk et al 1979), but its value has only recently been realized for ecological studies McIlwee et al 2001;Moore and Foley 2005). Excellent reviews of NIRS, which include ecological applications, are provided in Foley et al (1998) and Batten (1998).…”

Palatability mapping: a koala's eye view of spatial variation in habitat quality

“…In NIRS, statistical calibrations are established between nearinfrared spectra and qualitative or quantitative attributes of organic samples such as tree leaves. Because it is correlative, NIRS is ideal for predicting emergent properties of plant material, such as palatability or digestibility of foods (McIlwee et al 2001, DeGabriel et al 2008 or rates of decomposition (Stolter et al 2006), and it does not require a priori knowledge of the underlying chemistry. In this study, we used NIRS to develop an empirical calibration for palatability of foliage to koalas (i.e., voluntary dry matter intake of Eucalyptus foliage).…”

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

“…This would include an examination of the important wavelengths in the calibration equations, relating them to independent information on the chemistry of each source of material (e.g. McIlwee et al 2001). At this point there is not sufficient information to do that in this case, but it does not preclude the application of the method.…”

“…At this point there is not sufficient information to do that in this case, but it does not preclude the application of the method. Provided sufficient care is taken in calibration, and ensuring that samples to be predicted come from the same spectral population, then an understanding of the underlying mechanism, while desirable, is not essential (Foley et al 1998, McIlwee et al 2001.…”