Passage: The blue wildebeest is a herbivore, feeding primarily on the short grasses which commonly grow on light, and alkaline soils that are found in savanna grasslands and on plains. The animal's broad mouth is adapted for eating large quantities of short grass and it feeds both during the day and night. When grass is scarce, it will also eat the foliage of shrubs and trees. Wildebeest commonly associate with plains zebras as the latter eat the upper, less nutritious grass canopy, exposing the lower, greener material which the wildebeest prefer. Whenever possible, the wildebeest likes to drink twice daily and due to its regular requirement for water, it usually inhabits moist grasslands and areas with available water sources. The blue wildebeest drinks 9 to 12 litres of water every one to two days. Despite this, it can also survive in the arid Kalahari desert, where it obtains sufficient water from melons and water-storing roots and tubers.In a study of the dietary habits of the wildebeest, the animals were found to be feeding on the three dominant grasses of the area, namely : Themeda triandra, Digitaria macroblephara and Pennisetum mezianum. The time spent grazing increased by about 100% during the dry season. Though the choice of diet remained the same in both the dry and the wet season, the animals were more selective during the latter.

Question: What does a wildebeest primarily feed on?
short grasses