The ant-fungus mutualism is a symbiosis seen between certain ant and fungal species, in which ants actively cultivate fungus much like humans farm crops as a food source. Leafcutter ants use leaves as fertilizer to grow their crop — fungus. They cultivate their fungal gardens by providing freshly cut leaves, protecting them from pests and molds, and clearing decayed material. In return, the fungus acts as a food source for the ant larvae.