Dry season browsing by sable antelope in northern B otswana

The late dry season is a crucial period for grazing ungulates because the nutritional value of the remaining brown grass is lowest then and levels of crude protein and digestible organic matter may fall below the maintenance requirements of herbivores (Owen-Smith, 1982). During this adverse period, mixed feeders like impala (Aepyceros melampus) increase the proportion of browse in the form of the leaves of the woody plants they consume (Owen-Smith & Cooper, 1985). Crude protein levels are generally higher and seasonally more constant in foliage of woody plants than in grasses (Owen-Smith, 1982), but the foliage is commonly defended by tannins or spines that restrict consumption by grazers not adapted to cope with them (Cooper & Owen-Smith, 1985, 1986; Cooper, Owen-Smith & Bryant, 1988). Sable antelope (Hippotragus niger) are predominantly grazers and are distributed throughout southern African savannahs (Estes, 1991; Skinner & Chimimba, 2005) where the dry season is prolonged and ambient temperatures are high before the rains begin. Grass quality is especially poor on infertile, sandy soils (Bell, 1984). Sable typically depend on green grass persisting in drainage sump grasslands or in recently burned areas during the dry season (Estes & Estes, 1974; Parrini & Owen-Smith, 2009). However, contrary to previous reports, we observed a substantial amount of browsing by sable in our study area during the dry season. Here, we quantify the contribution made by browse to the diet of sable in our study area. Methods