Species Zebra Research Articles

Predation, sex ratios, and male competition in equids (Mammalia: Perissodactyla)

Existing data indicate that a greater preponderance of adult females rather than adult males occurs in most species of mammals. The hypothesis that such differences arise as a result of intermale reproductive competition for females (and not predation) was examined in the Equidae by comparing populations of horses (Equus caballus), asses (E. asinus), and two species of zebras (E. zebra and E. burchelli) in predator‐free, predator‐rich and insular ecosystems.Evidence is presented that: (1) sex differences in adult mortality occur; (2) they relate to the type and intensity of natural predation; and (3) asymmetries in sex ratios are most often explicable in terms of intermale reproductive competition. Exceptions are discussed and they are complicated by numerous proximate factors.

A unity underlying the different zebra striping patterns

To elucidate the relationship between the complex striping patterns of the different species of zebras, a simple conceptual experiment has been performed. Using data from horse embryos, the normal growth of the zebra from early foetus to adult has been reversed to see what happens both to the spacing and to the orientation of the stripes. It turns out that for each species, there is a point in time when all the body stripes would have been perpendicular to the dorsal line and equally spaced. Moreover the spacing is roughly the same (0·4 mm) for the three main species of zebra at this time. This point is during the third week of development for E. burchelli, fourth week for E. zebra and fifth week for E. grevyi. As striping only appears at about the eighth month of foetal development, it seems that the pattern is determined a long time before the cells actually lay down pigment. Further analysis of the pattern so laid down on a rapidly‐growing foetus shows how shadow and gridiron stripes can arise. The reason why leg stripes are orthogonal to body stripes cannot however be derived from this phenomenological approach. These results suggest that a single mechanism generating equi‐spaced stripes of separation 0·4 mm could lay down the body stripes of zebras and that species differences arise from pattern formation occurring at different times in embryogenesis.

Rangi: A Late Stone Age Site in Karamoja District, Uganda

Summary The Rangi site is situated on a hill slope below a cave on Kadam Mountain in north-eastern Uganda. Excavations yielded a microlithic industry with ‘Wilton’ affinities. Some iron implements and ostrich eggshell beads were also found. Ceramics are similar to Akira (‘TIP’) ware but also include middle to late Iron Age material. The non-domestic fauna includes a variety of bovids, zebra, warthog and other species. Three radiocarbon dates are anomalous, but when considered together suggest a post-fifteenth century date for the occupation of the site.

The buhen horse

The Buhen horse is well known to archaeologists. Its discovery was described by the late Professor W. B. Emery (1959, 1960) and the position it holds as the earliest horse to be found so far on an Ancient Egyptian site has been much quoted ( Drower, 1969; Epstein, 1971; Powell, 1971). A description of the skeleton, however, has never been published, although a short note was prepared by Speed (1963). The skeleton is the property of the Khartoum Museum from where it was kindly loaned to the Department of Egyptology, University College, London. The site was excavated by the Egypt Exploration Society under the direction of Emery in 1958 and 1959. The fortress of Buhen is near the second cataract of the Nile in the northern Sudan. It was built during the early part of the Middle Kingdom (2052-1786 BC) and was one of a series of trading posts and strongholds erected by the kings of the Twelfth Dynasty for strategic purposes. It was stormed and burnt down in about 1675 BC. A hundred years later the fortress was rebuilt for the New Kingdom army and it resisted further attacks until the Twentieth Dynasty (1085 BC) when it was finally destroyed. It was during the first sacking of the fortress in 1675 BC that a horse, that had perhaps been stalled between two bastions of the main fortress wall, was killed and fell to the ground, where its body lay on a brick pavement. It was covered with rubble and later the remains of the horse were sealed into this deposit by the brickwork of the New Kingdom reconstruction of the fortress. There can, therefore, be no dispute about its date. The first fact to establish was that it did represent a horse and not an ass or a zebra. The true horse was not an indigenous animal in Ancient Egypt, whereas the ass was common, both as a wild and as a domestic animal, and it is likely that Grevy's zebra (Equus grevyi) was also available. Of the several species of zebra, Grevy's has the most northerly distribution at the present day and it is also the largest; it would be quite plausible for its bones to be confused with those of a horse. The skeleton was therefore general structures as those which were introduced into India, Iran, northern Mesopotamia, Syria, Egypt and Greece during the same period.

Interrelationships of Two Zebra Species in an Overlap Zone

The distinctive Somali Arid and the East African grassland faunas approach each other to the north of the Kenya Highlands and along the Tana River. Both have unique endemics and many counterparts at the species and race level. Mostly these latter remain isolated but there are instances of intergradation and range overlap without interbreeding. An interesting case of the latter, that of the zebras Equus grevyi and E. burchelli, is analyzed here. The unusual feature of the zebra overlap is that mixed herds are formed. These maintain a level of constancy from day to day, and are not disrupted during flight. Mutual tolerance is marked. While mixed herds occur all year, the composition varies from season to season and district to district. Migrations may take place conjointly. Outside of the overlap zone habitat differences are marked. The mixed zebra herds of Kenya are contrasted with the zebra-wildebeest asso- ciations of the Kruger Park, South Africa, and it is shown that the former have greater cohesion and constancy.

Northern Rhodesia

Progress in the development of the Park is very satisfactory. The quantity and tameness of the animals in the southern section justifies the decision to open this section to the public, with limited facilities, for the 1953 Rhodes Centenary Exhibition. Numbers of all the local species of antelope, with buffalo and zebra, were seen without difficulty from July onwards till the rains broke. The game is definitely responding to the care taken for its preservation.

Procryptic Coloration a Protection against Lions.

THERE has been some interesting correspondence in recent numbers of The Field on the question of the procryptic coloration of big game, some writers taking one side and some another in the controversy. Now although there is a certain amount of evidence, scattered through sporting literature, showing that some species of African antelopes and zebras are hard for human beings to detect in particular surroundings, there is, so far as I am aware, scarcely any testimony, based upon observation in the jungle, to prove that the sight of predatory carnivora is baffled in the same way by colour assimilation.