|The gerenuk is endemic to Africa and is also known as the “giraffe gazelle” because of its distinctive, long neck and legs. It uses these lengthy appendages to forage tall herbaceous and succulent plants that most other antelopes can’t reach and is thus one of the most exclusive browsers.|
The gerenuk is one of the world’s most easily recognized antelopes due to its defining features, its long neck and long, thin legs.
The head is long and narrow with medium-sized ears, and the cheek teeth and masseter muscle are reduced.
The gerenuk’s coat is of a short, fine, glossy hair that is evenly distributed over the whole body.
The pelage is a pale tawny brown with white along the breast, underbelly, and inner legs. There are small, dark patches of fur on the knees of the forelegs and at the end of the tail. On the head there is a dark patch around the eyes that pales as it goes outward until it forms a white rim.
Both sexes of gerenuk are of similar size, but the males are more muscular than females causing them to outweigh them.
Mass ranges from 29 to 58 kilograms, total body length from 140 to 160 centimeters, and tail length from 220 to 350 millimeters.
Only male gerenuks have head ornamentation in the form of scimitar shaped horns ranging from 25 to 44 centimeters in length.
Giraffe Gazelle, Sclater’s Gazelle, Waller’s Gazelle
L. w. sclateri (Northern Gerenuk/Sclater’s gazelle)
L. w. walleri (Southern Gerenuk/Waller’s gazelle)
The gerenuk’s common name derives from the Somali name for the animal, gáránúug. The first recorded use of the name dates back to 1895.
The gerenuk is also known as the giraffe gazelle due to its similarity to the giraffe (Giraffa camelopardalis).
The gerenuk was first described by Victor Brooke in 1879 on the basis of three male specimens procured on the mainland of Africa, north of the island of Zanzibar. Brooke used the scientific name Gazella walleri, on the request of Gerald Waller who had provided the specimens and requested to name the species after his deceased brother.
The type locality was later corrected by John Kirk, who originally obtained the specimens on the coast near the River Juba in southern Somaliland before giving them to Waller.
In 1886, Franz Friedrich Kohl proposed a new genus for the gerenuk, Litocranius.
In 1997, Colin Groves proposed that Litocranius is a sister taxon of the similarly long-necked dibatag (Ammodorcas clarkei), but withdrew from this in 2000.
A 1999 phylogenetic study based on cytochrome b and cytochrome c oxidase subunit III analysis showed that the tribe Antilopini, to which the gerenuk belongs, is monophyletic.
In 2013, Eva Verena Bärmann and colleagues of the University of Cambridge revised the phylogeny of tribe on the basis of nuclear and mitochondrial gene analysis. The cladogram prepared by them showed that the springbok (Antidorcas marsupialis) forms a clade with the gerenuk. This clade is sister to the saiga (Saiga tatarica, tribe Saigini) and the blackbuck (Antilope cervicapra, genera Antilope,) Eudorcas, Gazella and Nanger (of Antilopini).
Two subspecies have been proposed for the gerenuk, but some authors considered these to be independent species. The boundary between the two named forms is not clearly defined.
The southern gerenuk (Litocranius walleri walleri) (Brooke, 1879) is also known as the Waller’s gazelle. Its range extends from northwestern Somalia (Berbera District) westward to touch the Ethiopian border and Djibouti.
The larger, northern gerenuk (Litocranius walleri sclateri) (Neumann, 1899), is also known as the Scalter’s gazelle. Its range extends through northeastern Tanzania through Kenya to Galcaio (Somalia). The range lies north of the Shebelle River and near Juba River.
The gerenuk formerly occurred widely in the semi-arid bushland of north-east Africa, from southern Djibouti to north-east Tanzania. The species was once found in eastern Egypt and northeastern Sudan, as well.
The gerenuk still occupies large parts of its historical range and inhabits the dry, brushy region of east Africa from the Serengeti plain of Tanzania north along the coast through Kenya, Ethiopia, Eritrea, and into southern Somalia. The northern limit of the range is about 11o30’N in Djibouti and the southern limit around Tarangire National Park (NP) in Tanzania.
It was described as the most common and most widespread antelope species across Somalia, but little recent information is available on its current distribution there and it was expected to have been severely reduced. The species remains widely but thinly spread in Somaliland, northern Somalia.
Gerenuk have never been an abundant species. At Tsavo National Park in Kenya, where the gerenuk is protected and enjoys good habitat, researchers have concluded that the species makes up less then 0.5% of the total biomass of hoofed mammals in the park.
The gerenuk population has been estimated at 24,000, based on aerial counts. That figure has been revised to 95,000 to account for under-counting bias in aerial surveys.
The species is difficult to census both from the ground and especially from the air, due to its often dense bush habitats, small group size and cryptic coloration.
Density estimates range from a maximum of 0.2/km² on aerial surveys to 1.0/km² from road counts and up to 8.0/km² in particularly favorable habitats, such as Samburu G.R. in Kenya. The largest surviving populations occur in south-western Ethiopia and the northern and eastern rangelands of Kenya.
Population trend may be generally stable in protected areas, with a few exceptions such as the declining population of Tsavo National Park, and slowly decreasing elsewhere. It’s been suggested a 50% decline in Kenya since 1970. In Tanzania, Gerenuks remain common in the Lake Natron area and fairly common in West Kilimanjaro, but have declined in the Makame depression in recent years because of over-hunting.
The gerenuk inhabits dry savanna and subtropical/tropical dry shrubland habitats including bushland, thickets, and semi-arid and arid thornush below 1,600 meters.
The habitat that the gerenuk occupies varies from the treeless plains of Tanzania in the southern reaches of its range to the dry high deserts of Kenya. They are adaptable and do well in a variety of habitats, provided there is a good supply of succulent plants.
The gerenuk avoids dense woodlands and very open, grass-dominated habitats.
The gerenuk is diurnal and primarily active during the day.
Because they do not form large populations and their food is of limited supply, gerenuk exhibit strange social interactions.
Males are solitary and very territorial. They only associate with females during the mating season or when they are young. Dominant males establish territories by marking trees and shrubs with their preorbital gland. Other dominant males will enter another’s territory without any aggression or defensiveness being displayed, but a young male without its own territory will be run off if he enters a dominant male’s territory. The size of a males territory can range from 300 to 850 acres and can support several individuals.
Females form small bands of up to about 10 individuals, usually related adults with young. These groups of females and young roam freely throughout male territories.
Young males that have just been weaned often form bachelor herds that roam nomadically until they become mature enough to establish their own territories and breed.
The gerenuk is herbivorous and an efficient browser of herbaceous and succulent plants.
The gerenuk is well adapted for obtaining forage from its arid habitats. Its long neck, long legs, and the ability to stand on its hind legs allows it to obtain tree leaves that are out of reach for most other antelope species. This permits gerenuks to be selective in the foods they eat and to be efficient browsers of herbaceous plants. As such, the gerenuk is one of the most exclusive browsers.
Over 80 different species of plants have been found in a single individual’s stomach.
One of the most exclusive browsers, gerenuk are largely independent of water. The gerenuk does not drink free-standing water and instead relies on water taken in when eating succulent plants.
The mating ritual of the gerenuk is complex.
When a male encounters a potential mate, the female will raise her nose into the air and pull her ears close to the head as a sign of defensiveness. Meanwhile, the male displays his horns and neck in a sideways pose. If the female is receptive, then the male will mark the female on the thigh with the contents of his preorbital gland and continue to follow her around, a form of mate guarding. As the male follows the female he continually uses his forelegs to kick the female in her thigh region.
When the female attempts to urinate, the male performs the flehmen test, or lip curl test, in which he samples her urine. Once the female comes into estrous, the male will notice the difference in the female’s urine and mating will begin.
Gerenuk reproduction and births occur throughout the year and may depend on the quality of available nutrition. Gerenuk females breed every one to two years, depending on the sex of their previous year’s offspring as male gerenuks are dependent on their mothers for longer than females. Females usually give birth to one offspring, rarely two, after a gestation period of about 165 days.
Gerenuks have maternal parental investment. Gerenuk mothers continue to look after their young until their weaned.
Young females get weaned when they reach one year of age, but male offspring are not weaned until they reach at least one and a half years old and stay with their mothers until after they are two.
Gerenuk young are precocial and begin to walk within minutes of birth.
Although rare, gerenuk contribute to nutrient cycling in the ecosystems in which they live through their foraging activity.
Gerenuk also act as prey species for large predators. Gerenuk are preyed on by a diverse set of large predators found throughout their range, such as cheetahs (Acinonyx jubatus), leopards (Panthera pardus), lions (Panthera leo), African wild dogs (Lycaon pictus), hyaenas, servals (Leptailurus serval), honey badgers (Mellivora capensis), caracals (Caracal caracal), and large eagles.
Gerenuk have evolved several anti-predator adaptations for survival as juveniles and as adults. Young gerenuk remain motionless while hiding in the bushes and tall grasses not far from their mothers during the day when the mother is feeding. As adults, they show an adaptation that is more common to forest dwelling antelopes than to desert-adapted ones, they freeze at the approach of danger.
There are no adverse effects of gerenuk on humans.
The gerenuk has been a game animal in Africa for over 200 years, though it’s not very common. Although they are limited in supply for hunters and have a limited range, they continue to be hunted for trophies and for bush meat, but levels of offtake are unknown.
Gerenuk have become a regular subject in the expanding world of photo-safaris and parks in Africa and help promote ecotourism.
Unfortunately, the gerenuk doesn’t do well in captivity and has rarely been bred in zoos.
The gerenuk is estimated to be close to meeting the threshold for Vulnerable on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species under criterion A2cd, based on a decline of at least 25% over the last 14 years, or three generations, calculated from 2002-2016. This decline is continuing due to hunting and habitat degradation caused by livestock grazing and cutting of trees.
The species is currently evaluated as Near Threatened.
The gerenuk can withstand hunting pressures to some degree which has enabled it to survive widely in regions such as the Ogaden in the complete absence of protection.
The gerenuk’s habitat is subject to encroachment by increasing numbers of pastoralists and cutting of trees for firewood and charcoal. Civil conflicts, wars, and unrest have affected much of the range in Somalia and the Ogaden over recent decades.
If current trends continue, the gerenuk may eventually disappear from large parts of its present distribution until it is largely restricted to effectively protected and managed areas of suitable habitat. Such areas currently comprise only a small part of its remaining range. The largest protected population, in Tsavo National Park, has been reduced by rinderpest and drought. Agricultural expansion, for example in the southern Masai steppe is encroaching on their habitat, but most of Gerenuk’s range is too arid to support agriculture.
As a game animal, the gerenuk is protected in most of its range in the form of tags or permits. About 10% of the gerenuk population occurs in protected areas.
There are many parks offering sanctuary for gerenuk within their range and many biologists and game managers studying them so they are not considered to be at significant risk currently. Important protected area populations occur in Mago NP and Awash NP (Ethiopia), Sibiloi, Tsavo and Meru National Parks and Samburu Game Reserve (Kenya) and Mkomazi Game Reserve and Tarangire NP (Tanzania). It can be favored by the spread of thickets following overgrazing by grasslands by livestock or removal of elephants by poaching.