Oryx dammah (Cretzschmar, 1826)

Don E. Wilson & Russell A. Mittermeier, 2011, Bovidae, Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona: Lynx Edicions, pp. 444-779 : 647

142.

Scimitar-horned Oryx

Oryx dammah

French: Oryx de Libye / German: Sabelantilope / Spanish: Oryx blanco

Taxonomy. Antilope dammah Cretzschmar, 1826 ,

Sudan, Northern Kordofan Prov.

This species is monotypic.

Distribution. Extinct in the wild. The Scimitar-horned Oryx originally occurred on the southern and northern edges of the Sahara Desert.

Descriptive notes. Head—body 159-175 cm, tail 37-44 cm, shoulder height 102-125 cm (males), ear 17-19. 5 cm, hindfoot 47-48 cm; weight 180-200 kg (males). Male Scimitar-horned Oryxes are generally larger than females. Both sexes have a mostly white face and head with an oxidized-red color on the bridge of the nose and over the eyes. The body is white, with the same reddish color on the neck and chest. Both sexes have long, slender (10-10. 8 cm thick at the base) horns, the longest of the oryxes (82-150 cm), that arch over the neck and shoulders and point to the hindquarters. Rings are present from the base through the lower one-third of the horn (about 35-40), more than on other oryx species. Being long and hollow, the horns can break easily. Preorbital glands are rudimentary, unlike other oryxes. The tail is white, like the rest of the body, and ends in a dark tuft of hair. Young Scimitar-horned Oryxes are mostly brown, with some white on the abdomen and black on their tails. Individuals greater than three months old can be identified by unique horn shapes and breaks, face markings, scars, and seasonal wear patches on shoulder pelage. Their coat changes to the adult coloration at about one year of age. Diploid chromosome number is 56-58; they are polymorphic for a centric fusion between chromosomes 2 and 15. The skull of the Scimitar-horned Oryx is comparable in size to that of most north-eastern African oryx species, but it has rather small teeth. Dental formula is 1 0/3, C0/1, P 3/3, M 3/3 (x2) = 32.

Habitat. Scimitar-horned Oryxes are aridland specialists. They formerly lived in the northern and southern sub-Saharan Desert, but did not inhabit the Sahara proper as does the Addax ( Addax nasomaculatus ). Limited rain falls for a short time during summer (150-500 mm/year in north and 250-500 mm/year in southern Sahel), and the oryx’s former range experiences long droughts; the most recent drought started in the 1960s and lasted through the early 1990s. Most of the former range has three seasons: a cold-dry season, a hot-dry season, and a rainy season. The rainy season in the northern parts of the former range begins in September, but it starts in June in the southern areas. Acacia raddiana, A. laeta and Commiphora africana are dominant plants, but sparsely distributed, on the northern edge of the Sahara, and Grewia bicolor, Adansonia digitata, Combretum micranthum, and C. glutinosum dominate in the south. These trees and shrubs were probably important to the Scimitar-horned Oryx for shade. In the wet season, herbaceous plants and annual grasses become plentiful—and were sought out as nutritious forage. Water is rare in the former range of the Scimitarhorned Oryx ; mesic areas exist, but are usually ephemeral. The southward spread of the Sahara Desert no doubt contributed to the demise of the Scimitar-horned Oryx .

Food and Feeding. Herbivorous. The Scimitar-horned Oryx is predominantly a grazer, but can be a facultative browser, depending on forage availability. When rainfall is sufficient, annual grasses and forbs are preferred. Favored plants at this time include Cenchrus biflorus, Panicum laetum, and Dactyloctenium aegyptium. In the wet season, Scimitar-horned Oryxes also eat Indigofera and Cordia sinensis. Precipitation occurs in different parts of their range throughout the year, and the oryxes seek foliage that grows with the rains. When the rains stop,its favored foods are usually still available until the hot-dry season. After the hot-dry season begins in March, these plants are less common, and the animals start to rely on perennial grasses and browse. Early in the hot-dry season, Scimitar-horned Oryxes will eat pods from Acacia raddiana. As the hot-dry season wears on, they will also eat Panicum turgidum and Aristida. They browse on Leptadenia, Cassia italica, and Cornulaca monacantha. When water is plentiful, they will drink long enough to impede their normal movement, but Scimitar-horned Oryxes can persist for months without drinking water, by eating plants with high moisture content, such as Citrullus colocynthis, a wild melon. The Scimitar-horned Oryx also obtains water by eating Boerhavia repens and Indigofera viscosa, ground-hugging plants covered in fine hairs that accumulate condensed moisture. Scimitar-horned Oryxes seek salt, and they will scrape away the upper layers of soil and consume salty layers below.

Breeding. Rut occurs during the cold season. Males test urine of females to detect estrus. Males fight by butting their heads; injuries may occur, but they are usually not fatal. In one case, a male Scimitar-horned Oryx shared an enclosure with Addaxes as part of a reintroduction effort. The male oryx courted an estrous female Addax and killed a male Addax that attempted to get near them. Gestation is 8-8-5 months. A pregnant female separates herself from the herd for up to a week. When she gives birth, a male may stand by and breed with her shortly after parturition. One offspring is usually born, but twins are possible (7% of captive births have been twins). Most births occur in a two-month window during the rainy season, thus assuring good forage for the lactating females. Neonates have horn stumps of 2-5 cm. They are able to walk a few hours after birth and run by five days of age, giving them the chance to escape from most predators. Young hide in sparse vegetation for two weeks postpartum and are able to run as fast as adults at about 20 days of age. Young are weaned at 2-10 months. Maternal attention is minimal. The young normally join a creche of similar-age individuals at about two weeks of age, presumably under minimal supervision. Females reach maturity at 11-30 months; males are sexually mature at 10-30 months. Scimitar-horned Oryxes in captivity can live up to 30 years of age; longevity in the wild is unknown but no doubt considerably less. One study of captive-born oryxes calculated a sex ratio of 1 male:0-84 female.

Activity patterns. Scimitar-horned Oryxes spend most of their time in search of food, primarily at night and in the early morning, when it is coolest. During the hottest part of the day, they seek shade to rest and ruminate. If shade is not available, they dig up a place next to vegetation to lie in. Long-distance movements mainly occur at night. Scimitar-horned Oryxes amble, nodding their heads when walking fast; they have a flowing trot.

Movements, Home range and Social organization. Scimitar-horned Oryxes once followed the rains in search of food, perhaps sensing changes in humidity; such movements may have been hundreds of kilometers. While on the move, they would go out of their way to avoid contact with humans. No data exist on their movement, activities, or ecology in the northern parts of their former range because they were extirpated before the start of the 20" century. In Chad, there were at least two populationsas late as the 1960s. The population that lived in the southern part of the country moved north during the hot season to meet the rain. The second population was located close to the northern range of the southern population, and it appeared to make long seasonal east-west movements. When sedentary, Scimitar-horned Oryxes formed herds of 10-30 animals. Larger herds of up to 100 individuals were not uncommon. During migration, groups of 1000 or more would aggregate. A dominant female appeared to lead the herd, but it may actually have been directed from the rear by the dominant male. Dominance followed a hereditary lineage. Based on a captive study, a four-year-old male normally was dominant. Older males were often forced out of the herd; bachelor herds formed occasionally, but they were not common.

Status and Conservation. CITES Appendix I. Classified as Extinct in the Wild on The IUCN Red List. The Scimitar-horned Oryx once ranged widely throughout the Sahara Desert, including extensive seasonal movements, except perhaps in the deep interior, and numbered about one million individuals. The southern part of the range ran through Mauritania (18° N-16° N), Mali (18° N-15° N), N Burkina Faso, Niger (17° N-15° N), Chad (17° N-14° N) and Sudan (18° N-15° N). The species also was found in Senegal and Morocco, near the Atlantic coast, and across Algeria, Tunisia, Libya, and Egypt. The main causes of extinction were human population growth, motorized access to the desert, and overexploitation. As human settlement increased, livestock took over fragile grasslands and other areas; desertification compounded these pressures. The last known wild individuals occurred in Chad and Niger in the mid-1980s. Because captive groups were established in zoos and in private collections throughout the world beginning in the 1960s, reintroduction is now possible. In the United Arab Emirates, more than 4000 occur in a private collection, and as many as 2000 occur on private ranches in Texas, USA. The Scimitar-horned Oryx has been returned to its native range, but only to six fenced locations of variable size: three in Tunisia (Bou-Hedma, Sidi Toui, and Oued Dekouk National Parks), with about 170 oryxes, one in Morocco (Souss-Massa National Park) with 240 animals, and two in Senegal (Ferlo and Guembuel reserves), with 30 animals. These groups receive different amounts of human attention. The eventual goal is reestablishment of free-ranging Scimitar-horned Oryxes in the wild.

Bibliography. Ansell (1972), Berg et al. (2008), Beudels-Jamar et al. (1998), El Algamy et al. (2008), Engel (2004), Estes (1991a, 1991b), Gilbert (2008), Gilbert & Woodfine (2004), Gillet (1966), Gordon (1993), IUCN/ SSC Antelope Specialist Group (2008am), lyengar et al. (2007), Molcanova & Wacher (2008), Morrow et al. (1999), Newby (1984), Wakefield et al. (2004).

Figures

138. Beisa Oryx (Oryx beisa), 139. Galla Oryx (Oryx gallarum), 140. Fringe-eared Oryx (Oryx callotis), 141. Gemsbok (Oryx gazella), 142. Scimitar-horned Oryx (Oryx dammah), 143. Arabian Oryx (Oryx leucoryx)

Distribution. Extinct in the wild. The Scimitar-horned Oryx originally occurred on the southern and northern edges of the Sahara Desert.