Tracking free-ranging sheep to evaluate interrelations between selective grazing, movement patterns and the botanical composition of alpine summer pastures in northern Italy

Abstract

Abstract Extensive sheep pasturing in alpine regions has a long tradition and fulfils numerous sociological, economic and ecological functions. The effects of sheep grazing on the floristic composition and vice versa depend on various factors. Knowledge of potential interrelations is crucial to developing adequate management systems to maintain pasture productivity and its unique biodiversity. The aim of the present study was to discuss the potential interrelations between movement and selective grazing behaviour of free-ranging unherded sheep and the botanical composition of high-altitude mountain pastures in northern Italy. General movement patterns were determined by using GPS tracking. The floristic composition of areas roamed by the sheep was analysed by collecting physical data during the summer of 2022. The energy content of ingested herbage biomass was determined based on faecal samples. Ranging between 2296 and 3015 m above sea level (a.s.l.), the average altitude used by the sheep was 2654 m a.s.l. Correlation analyses showed that the sheep used significantly higher altitudes with increasing temperature and sunshine duration and with decreasing air humidity and rainfall. A clear selective grazing behaviour was revealed, namely a preference for species with better nutritional attributes. Poa alpina was the most preferred species, while areas dominated by Nardus stricta were avoided. Furthermore, the sheep showed an uphill migration over the season, possibly caused by the delayed start of grassland growth at higher altitudes. Analyses of faecal samples revealed sufficient energy contents, presumably as a result of the targeted selection of nutritious plant species. Future studies should evaluate the feeding value of herbage on offer in order to validate the current results. The study highlights the opportunity of animal tracking in remote areas and provides indications for selective grazing of sheep under conditions of free choice.