Effects of global change on the diet of a mountain ungulatethe pyrenean chamois

Résumé

Herbivores play a fundamental role in maintaining the health and structure of ecosystems worldwide. However, recent evidence indicates that climatic and land-use changes are affecting biological systems across the globe at alarming rates, and more acutely in alpine ecosystems. Thus, predicting the impact of these changes on herbivores has become a key issue for the long-term conservation of ecosystems. Here, our main goal was to assess the impact of climate change and woody plant encroachment on the diet of a large alpine herbivore: the Pyrenean chamois (Rupicapra p. pyrenaica). We firstly compared and highlighted the limitations of two methodological approaches used in the determination of diet composition of herbivores (study 1). We then combined information from two monitored populations of Pyrenean chamois with multiple databases on seasonal phenology, climatic conditions, population abundance and models of habitat evolution to understand understand the effects of climate change and woody plant encroachment on the diet of this herbivore. Our results indicate that Pyrenean chamois is well adapted to the variations in the seasonal phenology of plants in alpine habitats (study 2), but that these patterns can be affected by environmental conditions. For instance, the seasonal presence of livestock may affect the diet of chamois during the co-habitation period (study 2). Concurrently, the variations in the vegetation onset and intra-specific competition are regulating factors of diet quality and composition during spring (study 3). Finally, we observed that woody plant expansion in unmanaged alpine grasslands will also affect wild and domestic herbivores during summer and autumn, but that the magnitudes and direction of these effects will vary depending of their dietary preferences (study 4). Overall, global changes are impacting the diet of alpine herbivores and could thus impact the performances of these species. We therefore reinforce the importance of integrating dietary studies when assessing species’ response to global changes. However, further studies would be necessary to assess the effect of these dietary adaptations on the species’ performance.