The roan antelope (Hippotragus equinus, Desmarest 1804), its ecology in the Waterberg Plateau Park

Erb, Karl Peter (1993-01)

Thesis (M. Sc.) -- University of Stellenbosch, 1993.

Thesis

ENGLISH ABSTRACT: This study was undertaken in the Waterberg Plateau Park in northern Namibia. Field work took place between January 1988 and September 1989; however relevant information collected since, has been included. The roan antelope population in the reserve stems from re introduced animals. A total of 93 were brought in between 1975 and 1981. By 1984 the population peaked at 275 individuals. 186 roan have since been captured and, sold. The main objective of the study was to develop a better understanding of the management requirements for this population of rare antelope. Approximately one-fifth (32 individuals) of the population was marked with eartags or plastic collars or both. Five animals were radio-collared. This is the first detailed study of. roan ante lope in such a large study area (40 000 ha), with such a large population and so many marked individuals. Chapter 3 deals with population dynamics. It is believed that the entire population was accurately counted, aged and sexed. The adult sex ratio was skewed in favour of females, despite the absence of predators large enough to kill adults. The majority of calves were born during the wet season, from the end of August to March. A positive relationship between early season rainfall and the calf crop in the subsequent year was found. The ratio of juveniles per 100 adult females averaged 4.1 over seven years. Recorded mortality was too small to identify significant factors. Two deterministic population models were developed for exploratory simulations and are presented in Chapter 4. Both simulations were fairly successful, giving good correlations with the actual counts. Nutrition is covered in Chapter 5. Simple nutrient budgets revealed that protein and phosphate requirements were probably not met in the dry season. Calculations based on hand selected forage samples and nutrient requirements of cattle, show that adult roan obtained 15-28% of their crude protein requirements and approximately 10% of the phosphate in the dry season. The social system of the roan is described in Chapter 6. Four different clans were recognized, each with a distinct home range. The breeding groups in each clan were unstable, splitting up and rejoining at random. Adult males exhibited territoriality during the breeding season, which is in contrast to most other studies where harem groups were observed. Outside the breeding season, dominant males rejoined bachelor groups or remained solitary. Home range size and configuration were described using different methods. Home ranges averaged 4800 ha for two clans _'0.-_. and the territory size of one male was estimated to be 1200 ha within a much bigger home range. Distinct wet - and_dry - season ranges could be distinguished. Habitat selection is discussed, and was determined primarily by feeding requirements. Forage quality was identified as the major limiting factor and thus the primary determinant of habitat use. In Chapter 7 management recommendations and research proposals are made to ensure sustainable utilisation, by both live capture and game viewing.

AFRIKAANSE OPSOMMING: Hierdie studie is in die Waterberg Platopark, in noordelike Namibie, uitgevoer. Veldwerk het tussen Januarie 1988 en September 1989 plaasgevind, maar relevante informasie wat daarna versamel is, is ingesluit. Die bastergemsbokpopulasie in die reserwe is afstarnmeling van diere wat hervestig is. n Totaal van 93 is tussen 1975 en 1981 ingebring. Teen 1984 het die populasie sy maksimum vlak van 275 bereik. 186 bastergemsbokke is sedertdien gevang en verkoop. Die hoofdoelwit van die studie was om 'n better begrip van die bestuursbenodighede van hierdie bevolking van 'n skaars boksoort te ontwikkel. Ongeveer 'n vyfde (32 individue) van die populasie is met oorplaatjies of plastiese nekbande of albei gemerk. Vyf diere is van radionekbande voorsien. Dit is die eerste keer dat 'n gedetaileerde studie van bastergemsbokke gemaak is in so 'n groot studiegebied (40 000 ha), met so 'n groot studiepopulasie en so baie gemerkte diere. Hoofstuk 3 handel oor populasie dinamika. Dit word aanvaar dat die hele populasie akkuraat getel en volgens ouderdom en geslag ingedeel is. Die volwasse geslagsverhouding was ten gunste van koeie , alhoewel groot roofdiere wat in staat is om volwasse bokke te vang, afwesig is. Die meerderheid kalwers word in die nat seisoen gebore, vanaf die einde van Augustus tot Maart. 'n Positiewe verhouding is gevind tussen vroee seisoen reenval en die kalweroes in die daaropvolgende jaar. Die verhouding van kalwers per 100 volwasse koeie was gemiddeld 41.1 oor sewe jaar. Die getal dooie diere wat gevind is, was te klein om wesenlike mortaliteitsfaktore te kon identifiseer. Twee deterministiese populasiemodelle is ontwikkel en word in Hoofstuk 4 voorgestel. Simulasie wat daarmee uitgevoer is, het goeie korrelasies getoon met werklike tellings. Voeding word in Hoofstuk 5 behandel. Eenvoudige begrotings van voedingsstowwe het getoon dat proteien- en fosfaatbehoeftes heelwaarskynlik nie altyd gedek word nie. Berekenings gebaseer op grasmonsters wat, met die hand versammelde is en behoeftes van beeste, dui aan dat volwasse bastergemsbokke in die droeseisoen slegs 15-28% van hulle ruproteien-en 10% van hulle fosfaatbehoefte kan dek. Die sosiale sisteem van bastergemsbokke word in Hoofstuk 6 beskryf. Vier verskiI lende stamme (clans) is uitgeken, elkeen met 'n eie tuisgebied. Die teelgroepe in elke stam was onstabiel en het sonder vaste patroon ontbind en weer gevorm. Volwasse bulle het hulle territorialiteit slegs gedurende die paringstydperk getoon. Dit is in teenstelling met die meeste ander studies waar haremgroepe waargeneem is. Buite die paringstydperk het dominante bulle weer by die vrygeselgroepe aangesluit of alleen gebly. Verski llende metodes is gebruik om die. grootte en konfigurasievan tuisgebiede te beskryf. Die tuisgebiede van twee stamme het gemiddeld 4800 ha beslaan. Die territorium van een bul is op 1200 ha beraam en het binne 'n baie groter tuisgebied gele. Afsonderlike nat- en droeseisoen tuisgebiede is geidentifiseer. Habitaatseleksie word hoofsaaklik deur voedingsbehoeftes bepaal. Voerkwaliteit is as die belangrikste beperkende faktor uitgeken en bepaal dus primer die keuse van habitaat. In Hoofstuk 7 word bestuurs- en navorsingsvoorstelle gemaak wat gemik is op die volgehoue benutting deur die vangs van lewende diere en besigtiging deur toueriste.

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