The gerenuk //, Litocranius walleri, also known as the Waller's gazelle, is a long-necked species of antelope found in dry thorn shrubland and desert in the Horn of Africa and the African Great Lakes region. The word gerenuk comes from the word in the Somali language, Garanuug, meaning "giraffe-necked". Gerenuk are sometimes also called the giraffe-necked antelope. It is the sole member of the genus Litocranius.
The gerenuk was first described by Anglo-Irish naturalist Victor Brooke in 1878. Its scientific name is Litocranius walleri. It is the sole member of the genus Litocranius, and is placed in the family Bovidae. In 1997, Colin Groves had proposed that Litocranius is a sister taxon of Ammodorcas, but reverted from this in 2000.
Two subspecies have been recognised:
- Litocranius walleri sclateri (Northern gerenuk) Neumsnn, 1899 : Its range extends from northwestern Somalia (Berbera District) and westward to just over the Egyptian border and Djibouti.
- Litocranius walleri walleri (Southern gerenuk) Brooke, 1878: Its range extends through northeastern Tanzania through Kenya to Galcaio in eastern-central Somalia, and lies north of the Shebelle River and near Juba River.
The gerenuk is a very tall gazelle-like antelope. Its long neck and long thin legs make it one of the most easily identifiable antelopes of the world. The head is long, flattened, narrow and wedge-shaped. It has large, skinny, rounded ears and white rings around its eyes. Females additionally have a dark patch on the crown. The tail terminates in a black tuft. Horns, found only on males, are curved backward and point forward, ending in hooked tips.  The reddish-brown to pale tawny coat is of short, fine, glossy hair spread evenly over the whole body. The underparts and the front of the neck are white. A dark band extends from the back partly down to the sides. On the dorsal midline of the neck are reversed hairs directed toward the neck.
Gerenuks seldom graze but browse on prickly bushes and trees, such as acacias. They can reach higher branches and twigs than other gazelles and antelope by standing erect on their rear legs and elongating their necks. They appear to favour the more tender leaves and shoots, but will also eat buds, flowers, fruit, and herbaceous plants. Gerenuks do not appear to drink water; they get enough water from the plants they eat. Because of this, they can survive in very dry habitats. Gerenuks are often prey for lions, cheetahs, jackals and leopards.
Gerenuk reproduce throughout the year. Females reach sexual maturity at around one year, and males reach sexual maturity at 1.5 years, although in the wild they may only be successful after acquiring a territory (perhaps 3.5 years). The gestation period is about seven months. They are born one at a time, weighing about 3 kg (6.6 lb) at birth. Offspring were produced through artificial insemination for the first time in 2010 at White Oak Conservation in Yulee, Florida. Four female calves were born, and one of the four was later inseminated successfully by White Oak and SEZARC (South-East Zoo Alliance for Reproduction & Conservation), creating a second generation of calves born from artificial insemination. Gerenuk can live 13 years or more in captivity, and at least eight years in the wild.
- IUCN SSC Antelope Specialist Group (2008). "Litocranius walleri". IUCN Red List of Threatened Species. Version 2012.1. International Union for Conservation of Nature. Retrieved 21 June 2012.
- Wilson, D.E.; Reeder, D.M., eds. (2005). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 682. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Groves, C.; Grubb, P. (2011). Ungulate Taxonomy. Baltimore, Maryland: Johns Hopkins University Press. p. 156. ISBN 9781421400938.
- Castelló, J.R. Bovids of the World: Antelopes, Gazelles, Cattle, Goats, Sheep, and Relatives. China: Princeton University Press. p. 156. ISBN 9780691167176.
- Leuthold, Walter (1978). "Ecology of the gerenuk Litocranius walleri". Journal of Animal Ecology 47 (2): 561–580. doi:10.2307/3801. JSTOR 3801.
- "One of our member institutions working with assisted reproductive techniques". Conservation Centers for Species Survival. Retrieved 3 June 2013.
- Media related to Litocranius walleri at Wikimedia Commons
- Gerenuk at Al Wabra Wildlife Preserve