Hartebeest & Gazelles

A herd of sunlit hartebeest. Laikipia county is at the intersection of two hartebeest subspecies (Alcelaphus buselaphus cokei) and (A. b. lelwel), one of only a few populations that constitute a hybrid zone whereby hartebeest initially diverged in allopatry and have come into secondary contact— in this case successfully interbreeding. See study here. Photographed after pursuit [3]

Hartebeest are an odd-looking antelope, with long faces and short-haired golden bodies. They are most closely related to the wildebeest and several other antelope I hadn’t heard of before (bontebok, tsessebe, & hirola), all three of which bear a somewhat similar appearance. Like much of the African megafauna, hartebeest populations all across its range are experiencing marked declines due to livestock and human encroachment on habitat. Additionally, efforts to restore predators such as lions have revealed an uneven predation pressure on herbivore prey, resulting in higher mortality of hartebeest. In what is termed apparent competition, co-occurring prey species indirectly affect each other through sharing a common predator. For example, one prey species may help maintain and increase the population of predators, which in turn has a disproportionate effect on a second prey species. This could result in the decline of that second prey species if it is preferentially preyed upon or if populations are unable to cope with a higher predation pressure afforded by first prey species.

Studies suggest apparent competition exists between hartebeest and other herbivores. In populations of hartebeest that spatially overlapped with plains zebra, lion predation on hartebeest greatly increased, while predation on zebra remained proportional to their population size. Hartebeest survival was greater when in tree cover away from glades, and yet hartebeest show a strong preference for glades and open grassland habitats. In Laikipia, woodland coverage has increased over time, providing another exacerbating factor for lion predation on hartebeest. Due to the great science that’s being done to reveal the effect of species interactions on hartebeest population dynamics, habitat preferences of hartebeest, and landscape change over time, conservation efforts to mitigate the hartebeest declines can be more informed and effective.

“Double hartebeest”, Ol Pejeta Conservancy, Kenya; photographed in situ [1]
Thomson’s gazelles, Ol Pejeta Conservancy, Kenya; photographed after slight disturbance [2]

Gazelles were generally much more skittish than the larger antelope, keeping a further distance away from humans. Pictured above is a herd of Thomson’s gazelles (Eudorcas thomsonii). They are often confused with Grant’s gazelles (Nanger granti) due to their similar appearance. Of the more notable differences, Thomson’s gazelles are smaller in body size, have facial black stripes that lie solely anterior to the eyes, and also more beige on the rear end in comparison to a mostly white rump in Grant’s gazelles.

Gerenuk (Litocranius walleri), Mpala, Laikipia, Kenya; photographed in situ [1]

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