During the periods of full moon from May to October 1980, black rhinoceroses were censused at all the important waterholes in the Etosha National Park. The results indicate an increase in the rhinoceros population which was substantially higher than expected. However, the high population in the west, where in some areas apparent over-utilization of the available food resource was evident. has since been affected by drought, anthrax and in particular poaching. From 1981 to June 1983, 17 mortalities relating mainly to unnatural causes were recorded, including 7 confirmed cases of poaching. As a consequence, in certain areas, many rhinoceroses have left traditional home ranges and a number of unrecorded mortalities are suspected. Control measures include the sucessful translocation of 29 rhinoceroses to the east of Etosha and in 1981, the vaccination of 36 rhinoceros against anthrax. With anti-poaching measures presently being inadequate, poaching poses the greatest threat to the black rhinoceros population. The implementation of effective anti-poaching measures has become a matter of urgency and is presently receiving attention.
Marking techniques of individuals. Colour-coded reflector discs 20 mm in diameter and 3.5 mm thick, were in- serted at the base of the anterior aspect of the front and the lateral sides of back horns of adult and sub-adult rhinoceroses, to facilitate the positive identification of translocated animals. Disc components comprised reflective tape, with printing plate at the back and transparent polycarbonate on the surface. Three colours, red, green and yellow, were used. With the aid of a torch, spotlight and binoculars, marked rhinoceroses were identified at night when they came to waterholes to drink. Because of horn wear, reflectors are temporary and function for approximately 6 months when affixed with epoxy resin 0.5 - 1.0 cm below the horn surface. Ear tags were unsatisfactory and mostly tore out, but are nevertheless recommended, particularly for marking calves and juveniles. Using reflectors, it was possible to plot the resettlement of 9 out of 10 rhinoceroses introduced to new surroundings in the Etosha National Park. The technique is recommended when monitoring and resettling rhinoceroses in arid and semi-arid environments, where they are required to drink at established water-points.
