Mammals
Gerenuk
Litocranius walleri · also called gerenuk, giraffe gazelle
The gerenuk solved a problem other antelopes could not — how to reach the leaves growing just out of everyone else’s range. It stands fully upright on its hind legs, steadies itself against a branch with a front hoof, and stretches a giraffe-like neck into foliage over two metres up. It barely ever drinks.
Overview
Gerenuks live in dry thornbush and semi-desert across the Horn of Africa and East Africa. About 80–105 cm at the shoulder, with a tiny head on a very long neck and long thin legs, they browse leaves and shoots from acacias and other thorny plants.
Browsing on two legs
It rises onto its hind legs, hooks a front hoof over a branch for balance, and feeds at 2 to 2.5 metres up — a layer no other gazelle-sized antelope can reach.
No water needed
It gets nearly all its moisture from leaves and metabolic water, and can live year-round where there is no standing water at all.
Status
The gerenuk is Near Threatened and decreasing, from overgrazing, land conversion, and drought across parts of its range.
Gerenuk: common questions
Why does the gerenuk stand on its hind legs to eat?
Standing upright on its hind legs lets the gerenuk reach a band of foliage, roughly 2 to 2.5 metres above the ground, that is above the reach of most other gazelle-sized antelopes but below the height that giraffes typically browse, effectively giving it near-exclusive access to that layer of leaves in its dry-bush habitat. It braces itself by hooking a front hoof over a branch or resting its forelegs lightly against the plant, and its body is specially adapted for this posture, with elongated legs, a long neck, and modified vertebrae and pelvis that allow it to balance and feed in the bipedal position for long periods without strain.
How does the gerenuk survive without drinking water?
The gerenuk is one of a number of desert-adapted antelopes that can meet essentially all of their water needs without ever drinking, by extracting moisture from the leaves, shoots, and buds they eat, which retain a useful water content even in dry country, and by producing metabolic water as a byproduct of digesting that food. It further conserves water through physiological adaptations such as concentrating its urine and producing dry faecal pellets, and by behavioural means like feeding in the cooler parts of the day and seeking shade. As a result, gerenuks can live year-round in areas where there is no surface water at all.
Do female gerenuks have horns?
No. Only male gerenuks carry horns, which are relatively short for the animal's size, thick at the base, and curve backward and then slightly forward at the tips. Females are hornless, which is common among gazelles and their relatives, where horns are primarily used by males in competition for mates and in defending small territories. Female gerenuks can still be readily identified by the same distinctive body shape, the very long neck, small head, large ears, and long slender legs, that makes the species unmistakable regardless of sex.
Is the gerenuk closely related to the giraffe?
No, despite the nickname giraffe gazelle and the shared feature of an unusually long neck used to browse high foliage, the gerenuk is a true antelope in the gazelle group, family Bovidae, while the giraffe belongs to a separate family, Giraffidae. The gerenuk's long neck is a case of convergent evolution, an independent solution to the same ecological problem of reaching leaves that shorter-necked browsers cannot, rather than evidence of a close relationship. The gerenuk's closest relatives are other gazelles and the dibatag, another long-necked antelope of the Horn of Africa.