The hirola (Beatragus hunteri), also called Hunter's hartebeest or Hunter's antelope, is a critically endangered antelope species found as of now, only in Kenya along the border of Somalia. It was first described by the big game hunter and zoologist H.C.V. Hunter in 1888. It is the only living member of the genus Beatragus, though other species are known from the fossil record. The global hirola population is estimated at 300–500 animals and there are none in captivity. According to a document produced by the International Union for Conservation of Nature "the loss of the hirola would be the first extinction of a mammalian genus on mainland Africa in modern human history".
Description The hirola is a medium-sized antelope, tan to rufous-tawny in colour with slightly lighter under parts, predominantly white inner ears and a white tail which extends down to the hocks. It has very sharp, lyrate horns which lack a basal pedicle and are ridged along three quarters of their length. As hirola age their coat darkens towards a slate grey and the number of ridges along their horns increases. Hirola have large, dark sub-orbital glands used for marking their territories and give them the name "four-eyed antelope". They have white spectacles around their eyes and an inverted white chevron running between the eyes. The horns, hooves, udders, nostrils, lips and ear tips are black. Males and females look similar although males are slightly larger with thicker horns and darker coats. Several sources have recorded precise measurements from both captive and wild hirola. The following are maximum and minimum values taken from all sources: height at the shoulder: 99–125 cm (39–49 in; 3.25–4.10 ft), body weight: 73–118 kg (161–260 lb), head and body length: 1.2–2 m (3 ft 11 in – 6 ft 7 in), horn length: 44–72 cm (17–28 in; 1.44–2.36 ft), horn spread (greatest outside width): 15–32 cm (5.9–12.6 in), tail length: 30–45 cm (12–18 in), ear length: 19 cm (7.5 in). It is not stated whether horn length was measured direct from base to tip or along the curve of the horn. There is no data on how long hirola live in the wild but in captivity they have been known to live for 15 years.
Taxonomy Authorities agree that the hirola belongs in the subfamily Alcelaphinae within the family Bovidae but there has been debate about the genus in which it should be placed. The Alcelaphinae contains hartebeest, wildebeest and topi, korrigum, bontebok, blesbok, tiang and tsessebe. When it was first described the hirola was given the common name Hunter's hartebeest. Despite this it was placed in the genus Damaliscus with the topi and given the scientific name Damaliscus hunteri. Newer theories have classified it as a subspecies of the topi (Damaliscus lunatus hunteri) or placed it within its own genus as Beatragus hunteri. Recent genetic analyses on karyotypic and mitochondrial DNA support the theory that the hirola is distinct from the topi and should be placed in its own genus. They also indicate that the hirola is in fact more closely related to Alcelaphus than to Damaliscus. Placing the hirola in its own genus is further supported by behavioural observations. Neither Alcelaphus nor Damaliscus engage in flehmen, where the male tastes the urine of the female to determine oestrus. They are the only genera of bovids to have lost this behaviour. Hirola still engage in flehmen although it is less obvious than in other species. The genus Beatragus originated around 3.1 million years ago and was once widespread with fossils found in Ethiopia, Djibouti, Tanzania and South Africa.
Ecology The hirola is adapted to arid environments with annual rainfall averaging 300 to 600 millimetres (12 to 24 in). Their habitats range from open grassland with light bush to wooded savannahs with low shrubs and scattered trees, most often on sandy soils. Despite the arid environments they inhabit, hirola appear to be able to survive independently of surface water. Andanje observed hirola drinking on only 10 occasions in 674 observations (1.5%) and all 10 observations of drinking occurred at the height of the dry season. Hirola do however favour short green grass and in 392 of 674 observations (58%) hirola were grazing on growths of short green grass around waterholes. This association with waterholes may have led to reports that hirola are dependent on surface water. Hirola are primarily grazers but browse may be important in the dry season. They favour grasses with a high leaf to stem ratio and Chloris and Digitaria species are believed to be important in their diet. Kingdon does not consider the ecological requirements of the hirola unusual and in fact considers them to be more generalist than either Connochaetes spp. or Damaliscus. A vet who examined the digestive tract of several hirola concluded that they were well adapted to eating dry region grasses and roughage. They feed on the dominant grasses of the region and Kingdon (1982) believes that quantity is more important than quality in the hirola's diet. Hirola are often found in association with other species, particularly oryx, Grant's gazelle, Burchell's zebra and topi. They avoid Coke's hartebeest, African buffalo, and elephant. Whilst hirola avoid direct association with livestock, they reportedly prefer the short grass in areas where livestock have grazed.
Social structure and reproduction Female hirola give birth alone and may remain separate from the herd for up to two months, making them vulnerable to predation. Eventually the female will rejoin a nursery herd consisting of females and their young. Nursery herds number from 5 to 40, although the mean herd size is 7–9. They are usually accompanied by an adult male.
Young hirola leave the nursery herd at around nine months of age and form various temporary associations. They may gather together in mixed or single sex herds of up to three individuals; sub-adult or subordinate adult males may form bachelor herds of 2-38 individuals; female sub-adults may join an adult male, and if no other hirola are present, young hirola may attach themselves to a herd of Grant's gazelles or simply spend most of their time alone.
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