Zebras eat primarily grasses and sedges but may also consume bark, leaves, buds, fruits, and roots if their favoured foods are scarce. Compared to ruminants, zebras have a simpler and less efficient digestive system. Nevertheless, they can subsist on lower-quality vegetation. Zebras may spend 60–80% of their time feeding, depending on the availability and quality of vegetation. The plains zebra is a pioneer grazer, mowing down the upper, less nutritious grass canopy and preparing the way for more specialised grazers, which depend on shorter and more nutritious grasses below.