关键词: 高寒草甸, 高原鼠兔, 营养生态位, 稳定同位素, 贝叶斯椭圆

Abstract: Understanding the nutritional niche relationships of plateau pikas (Ochotona curzoniae) at different population densities is crucial for comprehending their impact on grassland ecosystems and defining their ecological significance. This study investigates the nutritional niche characteristics of plateau pikas in the Qinghai-Tibet Plateau’s alpine meadow using stable isotope (¹³C and ¹⁵N) techniques. Results showed that ¹⁵N and ¹³C stable isotopes enrich the fastest in liver and muscle tissues and the slowest in fur and bones. High-density pika populations have significantly higher δ¹³C and δ¹⁵N values than medium and low density populations. In the low, medium and high density populations, the trophic level (δ¹⁵N range, NR), dietary diversity (δ¹³C range, CR), convex polygon area (total area, TA), and corrected standard ellipse area (SEA_C) reflected in the bone and fur tissues of the plateau pika were all higher than those in muscle and liver tissues. In the medium density population, the NR, CR, TA, and SEA_C in liver, muscle, and fur tissues of the plateau pika were the largest, while in the low density population, the above four nutritional niche indicators reflected in the bone tissue of the plateau pika were the largest. Stable isotope niche widths in liver, muscle, and fur tissues are much broader in medium-density populations than in high- and low-density populations, with niche overlap across three population densities of plateau pika. Bone and fur tissues exhibit higher niche overlap than muscle and liver tissues. We speculate that medium-density pika populations benefit from moderate disturbance effect, resulting in higher dietary diversity, nutritional niche width and area, thus better habitat suitability. It is recommended that local forestry and grassland authorities monitor medium-density pika populations (relative population density: 24. 94% - 37. 21%) and implement appropriate control measures to prevent irreversible damage to grasslands from overly high densities.

Key words: Alpine meadow, Plateau pika (Ochotona curzoniae), Trophic niche, Stable isotope, Bayesian ellipse