Trophic Ecology of a Threatened Specialist: Implications of the Dependence on Pappostipa frigida for the Conservation of Chinchilla chinchilla

Understanding trophic ecology is fundamental for the conservation of threatened species with specialist trophic strategies, such as the short-tailed chinchilla (<i>Chinchilla chinchilla</i>), a critically endangered rodent whose diet in the wild is poorly understood. This study presents the first integrated annual characterization of the dietary habits, trophic niche, and resource selection patterns of a high-Andean population. Plant availability was assessed, and dietary composition was analyzed via seasonal microhistological analysis of fecal samples. Diversity (Shannon-Wiener, H'), overlap (Schoener, PS), and resource selection (Manly's selection index) metrics were calculated. The results indicate a diet of very low diversity (H' < 0.1), stable throughout the year (PS > 0.99), and dominated (>77%) by grass <i>Pappostipa frigida</i>, with significant positive selection in all seasons. Shrub species, such as <i>Adesmia frigida</i>, were consistently avoided. This high degree of specialization reflects low functional plasticity and highlights the high vulnerability of <i>C. chinchilla</i> to environmental changes and habitat loss, underscoring that the conservation and restoration of <i>P. frigida</i> grasslands are imperative for the species' survival. Microhistological methodology is confirmed as a key tool for identifying critical trophic relationships and supporting conservation plans based on essential resources.