Factors Affecting Roan and Sable Antelope Populations on Nature Reserves in Transvaal with particular reference to ecophysiological aspects

Abstract

This study was carried out on four nature reserves in the Transvaal, South Africa, and the Matetsi area of northwestern Rhodesia, with information obtained from other areas. A high rate of mortality occurred amongst juveniles and, to a lesser extent, amongst adult sab 1 e. and roan an tel ope on Transvaal nature reserves. Four protozoal parasites were implicated in the mortalities. A high incidence of reservoir Cytauxzoon parasitaemia was observed in sampled sable and roan of various ages whilst Babesia infection occurred to a lesser extent with chlamydiosis and pneumocystosis being observed in one animal. It was determined that Cytauxzoon infection was transmitted via the placenta from dam to offspring. Post-mortem and histopathological examination of tissues from dead animals indicated that infectious diseases were secondary considerations in the mortality patterns, and that poor nutritional status was the prime factor involved. The incidence of parasitaemia of Rhodesian sable was of the same order as Transvaal sable, however, body condition of the former was considerably better than that of Transvaal sable. The nutritional status of sable and roan antelope was investigated in some depth. Data were o·btained from soil, water, forage and animal tissues (liver, blood and milk) collected from preferred dry-season feeding areas. The study adopted a screening approach to the aspect of nutrition and comparisons were made between areas to derive conclu$ions regarding the relationship of nutrition to disease and mortalities. The basic deficiencies on Transvaal reserves relate to protein, phosphorus and selenium. Sodium, calcium, magnesium, potassion, iron and copper are linked to the deficiency syndrome. Habitat quality, availability and utilization by sable and roan on Transvaal nature reserves was investigated. Preferred dry season feeding areas were measured ~ritically for various physical characteristics to elucidate the relationship between habitat use and nutritional deficiencies. Microscopic identification of plant fragments taken from rumens and caecums provided information that interspecific feeding competion existed in varying degrees between sable antelope and waterbuck, zebra and impala on Percy Fyfe Nature Reserve. Reproductive factors were investigated and it was determined that calving rate was of the order of 100 percent. Sable are seasonable breeders with a gestation period of only 8 months, while roan breed throughout the year and have a gestation period of approximately 275 days. Electro-ejaculation techniques were applied to sable males and it was determined that mature bulls are sexually capable of breeding throughout the year and subadult males reach physiological and psychological sexual capability as early as 16-19 months of age. Management considerations such as nutritional supplementation via salt blocks, range fertilization with super-phosphates and annnonium phosphates, range burning and control of competing species are discussed.