Specialized Feeding Behavior of an Endangered Primate Enhances Forest Health in China

A study on the long-term ecological impacts of specialized behavior can provide valuable insights for biodiversity conservation and ecosystem management, particularly in the context of climate change. The endangered primate Rhinopithecus bieti in temperate forest ecosystems relies primarily on the lichen Usnea longissima as its fallback food source. To investigate whether this specialized diet sustains forest health through trophic interactions, our study employed a three-tiered approach: (1) We first examined the impact of U. longissima on trees by comparing the health of branches covered with and without lichen. Findings reveal U. longissima exhibits harm to host trees, as lichen-covered branches displayed significantly higher rates of dieback. (2) Using habitats with varying extinction timelines of R. bieti, we quantified how the presence of R. bieti contributes to reducing U. longissima biomass. Results showed lichen biomass tripled in habitats where the species vanished 40 years ago compared to occupied habitats. (3) We finally used controlled artificial experiments that demonstrated that R. bieti's feeding activities may enhance U. longissima dispersal and growth. Our findings suggest that R. bieti may function as a natural regulator of lichen biomass, potentially helping to prevent overgrowth that could destabilize forest health. Notably, the monkeys' foraging behavior may not only control lichen proliferation but also help to promote its regeneration. This study underscores that restoring R. bieti populations would synergistically benefit both U. longissima viability and forest resilience, advocating for integrated conservation strategies that preserve specialized ecological interactions. Due to the fact that specialized diet species face severe survival challenges in the context of climate and environmental changes, future efforts should be focused on their ecological adaptation mechanisms and improving sustainable management strategies.