Grazing is the way herbivores feed on grasses and other low-growing plants. Browsing, by contrast, is feeding on the leaves and shoots of shrubs and trees. Some herbivores, such as elephants and impalas, eat both grasses and woody plants, so grazing and browsing are not always distinct.
These different feeding habits are reflected in the physiological differences between the animals. Grazers, such as cattle, sheep, zebras and wildebeests, often have broader muzzles (the front part of the face around the nose and mouth) that help them gather grass efficiently. Browsers, such as deer and giraffes, usually have narrower muzzles that help them select specific leaves and shoots among branches.
Across grasslands, savannas, tundra and wetlands, grazing influences which plants grow, where they grow and how tall they become. Grazers, like browsers, also affect their habitats by trampling vegetation and soil, spreading seeds and returning nutrients to the soil in their dung and urine. Together, these effects can create a patchwork of short and tall vegetation, open ground and denser plant cover, providing habitats for a variety of plants and animals.
When grazers become scarce, the plants they eat may grow taller or become dominant. The specific effects depend heavily on local conditions. In the Serengeti in East Africa, for example, when wild wildebeest numbers plummeted in the mid-20th century due to a devastating viral disease called rinderpest (as well as to poaching), dry grass accumulated and fires became more frequent. As wildebeest numbers recovered following the disease's eradication, their heavy grazing reduced the fuel available for fires, allowing tree density to increase.
When grazing is too intense or lasts too long, whether by wild populations or excessive livestock numbers, plants may be eaten faster than they can recover. Palatable species can decline, while less palatable or heavily defended plants take over. Heavy grazing can also reduce plant cover and leave soil vulnerable to erosion, although its effects vary greatly based on climate, soil type and animal movement patterns. By contrast, moderate, well-managed grazing can help maintain healthy grasslands and preserve rich biodiversity.