Browsing is the feeding on the leaves, soft shoots and twigs of shrubs, trees and other woody plants by herbivores. Grazing, by contrast, is feeding on grasses and other low-growing plants. Some herbivores, such as elephants and impalas, eat both woody plants and grasses, so browsing and grazing are not always distinct.
These different feeding habits are reflected in the physiological differences between the animals. Browsers, such as deer, goats and giraffes, usually have narrower muzzles (the front part of the face around the nose and mouth) or flexible lips that help them select specific leaves and shoots among branches. Grazers, such as cows and zebras, often have broader muzzles that help them gather grass efficiently.
Browsing directly affects forests, woodlands, shrublands and savannas by influencing which species grow, where they grow and how tall they become, thus playing an important role in the overall health of these ecosystems as well as in their carbon storage capacity.
As with grazers, browsers also alter their environments by trampling vegetation and soil, spreading seeds and returning nutrients via dung and urine. Together, these physical effects and feeding habits create open understories (the lower layer of vegetation beneath the trees), a mix of plant heights and varied microhabitats that support a wide range of wildlife.
When browsing is too intense or lasts too long, whether by wild herbivores or by domestic farm animals, woody plants may be stripped of leaves and shoots faster than they can recover. Preferred plant species can decline, while less preferred or heavily defended species, such as those with sharp thorns or toxic compounds, can become dominant.
Heavy browsing can also reduce the amount of vegetation growing at or near ground level and leave soil vulnerable to erosion, although its effects vary greatly based on climate, soil type and animal movement patterns. In parts of North America and Europe, for example, when large predator populations, such as wolves, declined and deer numbers surged, heavy browsing suppressed young tree growth and drastically altered lower forest layers, ultimately transforming entire forest ecosystems.
Conversely, when browser numbers decline, the woody plants they eat may grow unchecked or become dominant, with dense thickets and dead brush taking over where open spaces once existed. This can likewise greatly alter local ecosystems and can also increase the risk of high-severity wildfires in some environments.