Differential grassland use by livestock in Inner mongolian pastures: cattle seek biomass, sheep favor nutritional quality

Grazing is a major land use in natural grasslands; however, spatial use differences among livestock types and the underlying mechanisms in mixed grazing systems remain unclear. In this study, we used global positioning system-accelerometer collars, unmanned aerial vehicle-based multispectral remote sensing, and ground vegetation quadrats to quantify the spatial foraging patterns of cattle and sheep and identify their driving factors in a typical family ranch in Xilingol, Inner Mongolia. We found that the foraging behavior of cattle was significantly influenced by the aboveground biomass. They clearly tended to choose areas with high normalized vegetation index (NDVI) values, which are characterized by high vegetation coverage and productivity. In contrast, sheep exhibited a more uniform foraging distribution, favoring plant species with higher nutrient contents, particularly total nitrogen. Structural equation modeling revealed that grassland resources influenced livestock foraging not only directly as suggested by indicators such as the NDVI, but also indirectly by regulating plant nitrogen and phosphorus concentrations. Overall, cattle had a quantity-oriented foraging strategy, whereas sheep showed a quality-oriented preference. Our findings suggest that the NDVI and plant total nitrogen can serve as complementary indicators for grassland monitoring and degradation assessment in mixed grazing systems, providing a scientific basis for spatially explicit livestock allocation, overgrazing mitigation, and grassland restoration management.