Kobus leucotis (Lichtenstein & Peters, 1854)
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publication ID |
https://doi.org/ 10.5281/zenodo.6512484 |
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DOI |
https://doi.org/10.5281/zenodo.6636828 |
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persistent identifier |
https://treatment.plazi.org/id/03F50713-990B-FFB0-0341-FE8AF610FADA |
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Conny |
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scientific name |
Kobus leucotis |
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White-eared Kob
French: Cobe a oreilles blanches / German: Weiltohr-Moorantilope / Spanish: Kob orejiblanco
Taxonomy. Antilope leucotis Lichtenstein & Peters, 1854 ,
Swamps of the White Nile.
The White-eared Kob is sometimes given as a subspecies of K. kob , although it is elevated to species level here. Monotypic.
Distribution. SE Sudan and W Ethiopia; occasional groups are seen in N Uganda. The divisions between the ranges of the White-eared Kob, Loder’s Kob ( K. loderi ), and the Uganda Kob ( K. thomasi ) in Sudan are poorly understood. View Figure
Descriptive notes. Head-body c.160-180 cm, tail c.10-15 cm, shoulder height c.82-100 cm; weight 55 kg (males) and 40 kg (females). White-eared Kob males are significantly heavier than females; both sexes weigh less than the neighboring Uganda Kob , but body measurements are believed to be similar. Coloration shows extreme sexual dimorphism in this species. Juveniles and adult females are a golden brown to reddish color with white undersides. Dark markings are generally present on the front of the forelimbs. The face has paler markings around the eyes and ears. In contrast, mature males are rich black, sometimes with dark brown overtones. This dark pelage juxtaposes with the bright white underparts, meeting in a sharp line along the lower flanks. The inside surfaces of the legs are white and the outer surfaces are black, except for a white band just above the hooves. The face is prominently marked with white circles around each eye and ear. The White-eared Kob is aptly named; the backs of the ears of adult males are white. The lower face, including the lips, jaw line, and underside of the jaw, as well as a large patch on the upper throat, are white. Males begin the transition to this adult coloration at approximately three years of age; intermediate color phases are seen as they mature. In addition to their distinctive coloration, males can be identified by the presence of lyre-shaped horns. The horns emerge almost vertically from the forehead, curving backward then upward at the tips. Horn length in mature males is approximately 55 cm. Dental formulais 10/3, C0/1,P 3/3, M 3/3 (x2) = 32.
Habitat. Open grassland with scattered wooded areas. The White-eared Kob is found farther from permanent swamps than the similar sympatric Nile Lechwe ( K. megaceros ), but is rarely found more than 10 km from surface water. Dry season habitats (January— March) are typified by swampy Echinochloa pyramidalis meadows. During the wet season, White-eared Kobs migrate to Hyparrhenia rufa savannas interspersed with woodlands dominated by tree species such as Acacia sieberiana, Combretum fragrans, Balanites aegyptiaca, and Ziziphus mauritiana. Across its annual distribution, population densities are 5-20 ind/km?*. However, localized densities in excess of 1000 ind/km* may be found in areas near water during the dry season.
Food and Feeding. The White-eared Kob feeds primarily on grass. The leaves and stems of short stoloniferous grasses, such as Echinochloa pyramidalis and E. stagnina, are consumed year-round. Such grasses are especially important in the dry season as they continue to produce green shoots. Tall grasses like Hyparrhenia sp. are avoided if other options are available; when they are consumed, only the leaves are selected. A Whiteeared Kob will consume approximately 1 kg of vegetation per day (estimated during dry season). Their frequent grazing, especially in restricted dry season habitats, keeps grasses evenly mowed—Ieaves and stems are consistently cropped around 2-5 cm from the ground.
Breeding. The White-eared Kob reproduces in a broadly seasonal pattern; breeding is spread between January and April, with births coinciding with the late wet season (September—December). Throughout the mating season, males cluster together on small territories within traditional breeding grounds (leks). Estrous females show a distinct preference for central territories; these regions attract three times as many females as would be predicted based on a random distribution. Males tend to court individual females (rarely up to seven females may be present in a territory simultaneously) and actively try to prevent them from dispersing to neighboring males. Gestation is thought to be approximately eight months, based on that for the closely related Uganda Kob . A single young is typical, and neonates are tucked away in tall grass and thickets for several weeks. Weaning typically occurs by May orJune,just over six monthsafter birth. Females reach sexual maturity after their first year. Timing of male sexual maturity has not been measured, but social maturity (measured as the ability to hold a territory within a lek) does not occur until full mature coloration is achieved. Maximum life span in captivity is 16 years; individuals up to 13 years old have been noted in the wild.
Activity patterns. Active both day and night, usually with a rest during the hottest parts of the day. During the dry season, this activity pattern becomes particularly pronounced; individuals will feed in swampy meadows at night and move into wooded areas during midday. Females are significantly more active (walking and foraging) than males,likely due to the increased energy requirements associated with pregnancy and lactation.
Movements, Home range and Social organization. The migrations of the White-eared Kob represent the second largest migratory ungulate population in Africa after the Serengeti White-bearded Wildebeest ( Connochaetes mearnsi). Migratory movements are driven by the availability of water. Very large herds, containing at least 700,000 animals of both sexes and all ages, travel 150-200 km between dry and wet season ranges. During the dry season (beginning in January), White-eared Kobs concentrate along river systems in the northern parts of the species’ distribution; water and green vegetation are rare elsewhere. Typically confined to swampy meadows, unexpected rain (and subsequent vegetation growth) may cause temporary dispersal into surrounding areas. Territoriality among males is only observed during the dry season, when lek territories are occupied. Twenty to sixty-five males each defend a small territory within a lek; all are usually found within a rough circle only 100-250 m in diameter. Leks are usually located near prime feeding areas so as to attract females; their location may remain constant between years or shift with changing movement patterns. On the lek, levels of aggression are very high, particularly at the start of the breeding season. This 1s especially true on the central territories that achieve the highest breeding success: aggression may serve to disrupt adjacent males from successfully copulating or to attract mates from neighboring territories. Heavy rains, beginning in May and continuing into July, trigger the southward migration to drier wooded savannas; migration 1s thought to be a strategy to avoid areas with surface flooding. The northward migration back to the swamp meadows usually begins in October; infants are born during this migration, which may increase neonatal survival by reducing the impacts of predation.
Status and Conservation. Classified as Least Concern on The IUCN Red List (as K. kob leucotis ). Despite having the smallest range of the four kob species, the White-eared Kob is the most numerous. The current population in southern Sudan is estimated to be at least 753,000 animals, most occurring around Boma National Park. This is a slight decline from estimates made in 1985, when the Boma population exceeded 800,000. The preferred habitats and transient nature of the White-eared Kob offer much protection because large areas are relatively inaccessible to humans. This species is heavily hunted in some regions, but the harvest appears to be less significant to population numbers than the limitations imposed by food resources during the dry season. The most notable decline in numbers has been in the eastern periphery of the species’ range in Ethiopia.
Bibliography. East (1999), Fay et al. (2007), Fryxell (1985, 1987), Green & El-Moghraby (2009), IUCN/SSC Antelope Specialist Group (2008z), Kingdon (1982), Leslie, Bowyer & Jenks (2008), Lydekker (1914), Weigl (2005).
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