Vegetation restoration measures: Increasing plant height suppresses population densities of plateau pikas

Abstract Plateau pikas ( Ochotona curzoniae ) are often regarded as pests when their population densities exceed a certain threshold. Vegetation restoration measures are commonly used for the ecological control of pikas. Nevertheless, it is not known how effective these measures are, and if effective, which factors are responsible for the decline in pika densities. Four commonly used grassland restoration measures: exclosure [E], exclosure/fertilized [EF], exclosure/overseeding [EO], exclosure/fertilization/over‐seeding [EOF], were implemented in grasslands degraded by high densities of pikas, and the pika density (PD) and vegetation traits in each treatment plot were monitored for 4 consecutive years. Neither the PD nor the vegetation composition was affected by any of the vegetation restoration measures within the first year. From the second year onwards, all the vegetation restoration measures had a significant effect on the vegetation composition and structure, such as an increase in the height, cover, and biomass. All the vegetation restoration measures, except E, had a significant suppressive effect on pika densities as time progressed, with the combination EOF measure having the largest effect. The stepwise regression analysis indicated that the vegetation height is the main factor that determines the PD. Similarly, structural equation modelling showed that vegetation restoration measures reduce PD primarily by increasing vegetation height. This may be because the height of the vegetation is closely correlated to the predation risk of pikas. Our results highlight the importance of vegetation height in pika management, suggesting that the key to successful pika management is to find a sustainable grazing system, which is beneficial to the growth of the dominant graminoids and maintains a high plant diversity for the sustainability of grassland ecosystems.