hartebeest to inspect its surroundings continuously even as it is grazing. The muzzle has evolved so as to derive maximum nutrition from even a frugal diet. The horns are also used during fights among males for dominance in the breeding season; the clash of the horns is loud enough that it can be heard from hundreds of metres away. The beginning of a fight is marked with a series of head movements and stances, as well as depositing droppings on dung piles. The opponents drop onto their knees and, after giving a hammer-like blow, begin wrestling, their horns interlocking. One attempts to fling the head of the other to one side to stab the neck and shoulders with his horns. Fights are rarely serious, but can be fatal if they are. Like the sassabies, hartebeest produce quiet quacking and grunting sounds. Juveniles tend to be more vocal than adults, and produce a quacking call when alarmed or pursued. The hartebeest uses defecation as an olfactory and visual display. Herds are generally sedentary, and tend to migrate only under adverse conditions such as natural calamities. The hartebeest is the least migratory in the tribe Alcelaphini (which also includes wildebeest and sassabies), and also consumes the least amount of water and has the lowest metabolic rate among the members of the tribe. Parasites and diseases Several parasites have been isolated from the hartebeest. These parasites regularly alternate between hartebeest and gazelles or wildebeest. Hartebeest can be infected with theileriosis due to Rhipicephalus evertsi and Theileria species. South of the Sahara, common parasites include Loewioestrus variolosus, Gedoelstia cristata and G. hassleri. The latter two species can cause serious diseases such as encephalitis. However, parasites are not always harmful – 252 larvae were found in the head of one Zambian individual without any pathogenicity. Nematodes, cestodes, paramphistomes; and the roundworm Setaria labiatopapillosa have also been isolated from the hartebeest. In 1931, a red hartebeest in Gobabis (southwestern Africa) was infected with long, thin worms. These were named Longistrongylus meyeri after their collector, T. Meyer. Diet Hartebeest are primarily grazers, and their diets consist mostly of grasses. A study in the Nazinga Game Ranch in Burkina Faso found that the hartebeest's skull structure eased the acquisition and chewing of highly fibrous foods. The hartebeest has much lower food intake than the other members of Alcelaphini. The long thin muzzle of the hartebeest assists in feeding