Abstract: The number of wild large herbivores, including Equus kiang, Procapra picticaudata and Pseudois nayaur was investigated using remote sensing technology or an unmanned aerial vehicle (UAV). The balance of grassland-livestock, including wild and domestic herbivores, was estimated from data (30 m resolution) in Maduo County in 2016 and the effects of wild herbivore population on the balance of grassland-livestock analyzed. The population of large herbivores was estimated from animal density from sample flights, and the results compared with data from summer monitoring. The estimated number of E. kiang, P. picticaudata and P. nayaur were 1.71, 1.60 and 0.93 million respectively, while the number of yak, Tibetan sheep and horses were 7.08, 10.22 and 0.12 million respectively. The number of large wild herbivores present was equivalent to 47.5 million sheep stock units. The ratio of sheep stock units from wild herbivores to the number of domestic herbivores was 1∶4.5. The carrying capacity index of domestic livestock was 1.13, indicating that the grassland was slightly overstocked; the carrying capacity index for wild herbivores was 0.25 and the combined carrying capacity index (1.38) indicated that the grassland was overstocked. Not including wild herbivores in the grassland-livestock balance accounting system resulted in the carrying capacity index being underestimated by 22%. Overstocking is one of the main drivers of grassland degradation in Maduo County; feeding of 79000 tons of hay or reducing livestock numbers by 30% would be required to achieve balance.

Key words: remote sensing of UAV, large-scale wild herbivores, population number, grassland-livestock balance, the source Region of the Yellow River