Supplementary Material for: A Short Cut to Mushrooms – Red Langur (Presbytis rubicunda) Consumption of Terrestrial Fungus

We report the first in-depth evidence of targeted mushroom foraging in an Asian colobine. Using direct observations (2010–2018) and camera traps (2008–2018) in the Sebangau Forest, Central Kalimantan, Indonesian Borneo, we show how adult female red langurs (Presbytis rubicunda) are regularly descending to the ground to consume mushrooms. We recorded 82 counts (0.36% of all focal observations, n = 25,502) of the focal adult langur on the ground from direct observations of habituated groups, and 80 independent images/videos of red langurs on the ground were obtained from the camera traps representing 1.12% of total images (n = 7,145). Mushroom consumption took place in 4 families, representing 0.04% of total focal behaviour observations and 24.3% of total time feeding on the ground. From the camera trap photos, red langurs are spending 20% of time on the ground feeding. We speculate that mushrooms could be a supplementary food for adult female langurs as there is an increase in consumption in April and November.