Food for folivores: nutritional explanations linking diets to population density

Wallis, Ian R., Edwards, Melanie J., Windley, Hannah, Krockenberger, Andrew K., Felton, Annika, Quenzer, Megan, Ganzhorn, Joerg U., and Foley, William J. (2012) Food for folivores: nutritional explanations linking diets to population density. Oecologia, 169 (2). pp. 281-291.

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Ecologists want to explain why populations of animals are not evenly distributed across landscapes and often turn to nutritional explanations. In seeking to link population attributes with food quality, they often contrast nutritionally positive traits, such as the concentration of nitrogen, against negative ones, such as fibre concentration, by using a ratio of these traits. This specific ratio has attracted attention because it sometimes correlates with the biomass of colobine primates across sites in Asia and Africa. Although empirically successful, we have identified problems with the ratio that may explain why it fails under some conditions to predict colobine biomass. First, available nitrogen, rather than total nitrogen, is nutritionally important, while the presence of tannins is the major factor reducing the availability of nitrogen in browse plant species. Second, tannin complexes inflate measures of fibre. Finally, simple ratios may be unsound statistically because they implicitly assume isometric relationships between variables. We used data on the chemical composition of plants from three continents to examine the relationships between the concentrations of nitrogen, available nitrogen, fibre and tannins in foliage and to evaluate the nitrogen to fibre ratio. Our results suggest that the ratio of the concentration of nitrogen to fibre in leaves does sometimes closely correlate with the concentration of available nitrogen. However, the ratio may give misleading results when leaves contain high concentrations of tannins. The concentration of available nitrogen, which incorporates measures of total nitrogen, dry matter digestibility and tannins, should give a better indication of the nutritional value of leaves for herbivorous mammals that can readily be extrapolated to habitats.

Item ID: 22709
Item Type: Article (Research - C1)
ISSN: 1432-1939
Keywords: herbivory, nitrogen, tannin, polyethylene glycol, folivore
Funders: Australian Research Council (ARC), Marine and Tropical Science Research Facility
Date Deposited: 01 Aug 2012 09:52
FoR Codes: 06 BIOLOGICAL SCIENCES > 0608 Zoology > 060899 Zoology not elsewhere classified @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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