Dibatag

The dibatag (Ammodorcas clarkei), or Clarke's gazelle, is a medium-sized slender antelope native to Ethiopia and Somalia. Though not a true gazelle, it is similarly marked, with long legs and neck. It is often confused with the gerenuk due to their striking resemblance. The typical head-and-body length is about 103 to 117 cm (41 to 46 in). They stand up to about 80 to 90 cm (31 to 35 in). Male dibatag weigh between 20 and 35 kg (44 and 77 lb), whereas females range from 22 and 29 kg (49 and 64 lb). The length of the curved horns, present only on males, is typically between 10 and 25 cm (3.9 and 9.8 in). The upper parts are gray to fawn, while the dorsal and lateral areas are cinnamon to rufous (reddish brown). The underparts, rump and the insides of the legs are all white. While markings are visible on the face, there are none on the flanks or the buttocks.

Dibatag are alert and secretive, and their brown coat provides an excellent camouflage, making the dibatag one of the antelopes most difficult to hunt. They are diurnal animals, and navigate in very small herds. Both sexes attain sexual maturity at 12 to 18 months. The species is polygynous. After a gestational period of six to seven months, a single offspring is born. Parturition usually occurs from September to November. The lifespan typically averages 10 to 12 years. Dibatag may maintain temporary territories demarcated by preorbital gland secretions, urine or feces. Primarily browsers, the dibatag feed on foliage and young shoots and shrubs. Dibatag are well adapted to semi-arid habitats, with the capability of surviving on very little or no water.

Several factors including human settlement, habitat degradation, large numbers of livestock, political unrest and armed conflicts in the areas covering its range and lack of conservation measures for two to three decades in the late 20th century have now reduced the population to only a few thousand. Significant populations still occur in southern Ogaden (Ethiopia). The dibatag is listed by the IUCN as "Vulnerable".

The dibatag was first described in 1891 by British zoologist Oldfield Thomas, who gave it the scientific name Ammodorcas clarkei. It is the sole member of the genus Ammodorcas, and is placed in the family Bovidae. Some authors such as Rod East of the IUCN SSC Antelope specialist group have classified it under a separate tribe Ammodorcadini. When Thomas first studied specimens from Somalia in 1891, he observed that the animal seemed to combine the horns of a reedbuck with the characteristic features of a gazelle (muzzle, facial markings, and anteorbital glands). At first, he considered it to be a reedbuck, though it appeared unnatural that a reedbuck should occur in the dry sandy plateau of Somalia. Thomas originally considered it a relative of the genus Redunca due to similarities in the morphology of horns, and placed it under the genus Cervicapra. However, after considering further specimens, he placed it under the separate genus Ammodorcas. No subspecies have been identified.

The dibatag, which holds its black tail straight up when it is fleeing, gets its common name from the Somali words for 'tail' and 'erect': dabu and tag. The dibatag is also known as Clarke's gazelle, after T. W. H. Clarke, an Australian big game hunter who collected the type specimen.

The dibatag is a medium-sized antelope with a slim body and long neck and legs. The typical head-and-body length is about 103 to 117 cm (41 to 46 in). It stands up to about 80 to 90 cm (31 to 35 in) at the shoulder. The male weighs between 20 and 35 kg (44 and 77 lb), whereas the female ranges from 22 and 29 kg (49 and 64 lb). The long dark tail ends in a rounded but indistinct tassel. The tail is nearly 30 to 36 cm (12 to 14 in) long. The curved horns, resembling those of reedbuck, are present only on males, with the pointing tips facing forward. The length of horns is typically between 10 and 25 cm (3.9 and 9.8 in), though Rowland Ward recorded a length of 33 cm (13 in) from Somalia. This antelope is sexually dimorphic, because females tend to be smaller than males and lack horns.

The species has a small, flat, pointed, wedge-shaped head with large eyes and medium-sized ears. A similarity to the gazelles is the black, branched structure in the interior of the ears. The mouth is very small and the upper lip slightly elongated. There are strong facial markings resembling those of a gazelle. A chestnut brown streak runs from the crown up to the nostrils along the nose, flanked on both sides by parallel white stripes that circle the eyes. A white spot marks the throat. The soft and smooth coat is gray to fawn in the upper parts. The ventral side, rump and the insides of the legs are completely white, and the flanks and the buttocks are unmarked.

The dibatag closely resembles the gerenuk, with which it is sympatric in eastern and central Somalia and southeastern Ethiopia. Both are brachyodonts and share several facial and cranial features, along with a two-tone coloration of the pelage and strong thick horns (only in males). However, there are also some features distinguishing it from the gerenuk, including major morphological differences in horns, horn cores, tail, postorbital area and basioccipital processes. The gerenuk has a longer, heavier neck and a shorter tail. A finer point of difference is the absence of an inward-curving lobe in the lower edge of the ear (near its tip) in the gerenuk.