The gerenuk (Litocranius walleri) is an unusually looking long-necked antelope found in the Horn of Africa and the drier parts of East Africa. The gerenuk was first described by the naturalist Victor Brooke in 1879. The common name derives from the Somali name for the animal (gáránúug). It is also known as the "giraffe gazelle" due to its similarity to the giraffe.
The gerenuk is a notably tall, slender antelope that resembles gazelles. It is characterized by its long, slender neck and limbs, the flat, wedge-like head, and the large, round eyes. Two types of coloration are clearly visible on the smooth coat: the reddish brown dorsal parts (the back or the "saddle"), and the lighter flanks, fawn to buff. The underbelly and insides of the legs are cream in colour. The eyes and the mouth are surrounded by white fur. Females have a dark patch on the crown. The horns, present only on males, are lyre-like ("S"-shaped). Curving backward then slightly forward, these measure 25-44 cm (10-17.5 in).
The natural range of gerenuk covers the Horn of Africa, stretching from southern Djibouti, Somalia, and Ethiopia to as far south as Kenya and the north-eastern portions of Tanzania. Within this territory, these antelope inhabit thickets, thornbush and tend to avoid dense woodlands and very open, grassy areas.
Gerenuk are highly social creatures, forming small, single-sex herds of 2-6 individuals, although all-female herds may sometimes contain juveniles. Meanwhile, males occasionally prefer living solitarily. Gerenuk are generally peaceful and rarely fight. They are sedentary and don't tend to travel, apparently in order to conserve enough energy for foraging. They become even less mobile as they age. Each herd has its own territory, typically 3-6 square km (1.2-2.3 square miles) in size. Home ranges of various herds often overlap. Males defend their territories by scent marking with special secretions, produced by their preorbital glands. Gerenuk lead a diurnal lifestyle, which means that they are active by day. However, they spend the midday hours standing or resting in shelters. The greater part of their active time is spent looking for food and eating. Meanwhile, female gerenuks appear to spend more time in these activities than males. In order to cool off, they often expose themselves to rain.
Gerenuk have a polygynous mating system, where each male mates with a number of females. They may breed at any time of year, although each female breeds once every 1-2 years. Intervals between breeding are related to the gender of the previous year's young. The gestation period lasts for 165 days, yielding 1-2 calves, which are born fully developed. During the first few minutes after birth, they are able to walk. The young are cared for and fed by their mother until weaning, which occurs at 1 year old in females and at least 1.5 years old in males. The latter don't leave their mother until 2 years old. The age of reproductive maturity is 1-2 years old in females and 1.5 years old in males. Males in the wild typically start mating only at 3.5 years old, when they are dominant enough to occupy a maintain of their own.
Gerenuk are primarily threatened by loss and fragmentation of their natural habitat, associated with growth of local human populations, leading to the development of settlements, roads and agriculture. As a result, some isolated populations cannot find suitable food and shelter. Some are unable to find mates as well as escape predators. Further, this species has served as a game animal in Africa for a long period of more than 200 years. In spite of having limited supply and very small natural range, gerenuks heavily suffer from hunting as trophies and for consumption.
According to the IUCN Red List, the total population of the gerenuk is around 95,000 individuals. Currently, this species is classified as Near Threatened (NT) and its numbers are decreasing.
Despite the small overall population, gerenuk play an important role in the local ecosystems. Thus, due to foraging, gerenuks enhance nutrient cycling. Then, they are key prey species for numerous predators of their range (leopards, lions, hyenas, and others).