Collection of plant biomass and faecal pellets
For the analysis of nutrients and stable isotopes, we selected 7 burrows with visible signs of recent marmot presence (fresh faeces) to collect plant biomass samples and faecal pellets: 4 burrows from the high cluster and 3 from the low cluster. To exclude the possibility of cumulative influence of burrows, we chose burrows that were further than 50 meters from the entrance of the closest burrow with fresh faeces. Around each burrow, we selected 2-4 dominant plant species/genera, and we collected about 10 samples of aboveground green biomass from each (Table 1). Samples were collected at different distances from the burrow entrance, up to 20 m (Fig. 1C). We collected 171 biomass samples from 8 plant species/genera in 20 combinations of burrow and plant. From each mound of the selected burrows, we collected 10 randomly selected fresh faecal pellets.