Volume 32, Issue 1, April 2002

The status and population structure of the marula in the Kruger National Park
Jacobs, O.S.Biggs, R. 1-12

Abstract: The South African National Parks identified the need for autecological studies on specific rare indicator keystone plant species. The marula is one of the preferred tree species particularly selected for by elephant and whose current damaged condition and disappearance in a mature state in the Kruger National Park is causing serious concern. The density of marula trees and the current population structure of this tree species were examined in four major landscapes of the Kruger National Park. Results indicate that the marula population in the Colophospermum mopane shrubveld has become virtually extinct, while the Colophospermum mopane /Acacia nigrescens savanna has a markedly unstable population with a lack of immature trees. The marula populations in the southern landscapes (mixed Combretum/Terminalia sericea woodland and Sclerocarya birrea/Acacia nigrescens savanna) appear to be healthy. The population structures on the different substrata (granite and basalt) differed significantly. Results of this study further indicate that diversity of vegetation plays an important role in determining herbivory pressure, and consequently in influencing the marula population structure

The impact of the African elephant on marula trees in the Kruger National Park
Jacobs, O.S.Biggs, R. 13-22

Abstract: Previous vegetation studies in the Kruger National Park have shown a dramatic decline in the density of large trees in four major vegetation units of the Park. An assessment of the damage status of Sclerocarya birrea (marula), identified as one of the most important tree species in the Kruger National Park, was conducted across three major landscapes of the Park. Previous studies indicated that marula were most utilized by elephants, resulting in weak regeneration and recruitment, with consequent changes to the population structure of the species. Furthermore, results indicated that the marula populations in two major landscapes of the Kruger National Park were threatened. The objective of this study was to generate a data set, which can be used in conjunction with future monitoring, to quantify the elephant damage to the marula population in the Kruger National Park. Results indicated that almost half the surveyed population suffered from damage due to elephant activity, predominantly in the form of bark stripping and felling. Felling resulted in a large proportion of marula trees being reduced to a height of less than five metres. Main stem breakage by elephant was the main cause of the 7% mortality observed in the marula population.

Estimating impact of reintroduced elephant on trees in a small reserve
Duffy, K.J.Van Os, R.Vos, S.Van Aarde, J.Ellish, G.Stretch, A-M.B. .23-29

Abstract: The reintroduction of elephant (Loxodonta africana) to small game farms and reserves is a growing trend in southern Africa. Issues over elephant conservation in general are controversial. Where poaching is less prolific and elephant are restricted to relatively small regions, the main concern is that elephant could drastically alter their environment by destroying trees with the possibility of decreasing biological diversity. In this paper we show how the analysis of transect data can help assess the impact of newly introduced elephant. Trees utilized by elephant are highlighted. It is found that for the region considered, only Sclerocarya birrea (marula) is being removed at a rate higher than 0.04 per annum (upper limit of annual regeneration). This tree is relatively rare and urgent work is needed to assess its status. Other rare trees should also be studied. The geographical characteristics of the region are fairly homogeneous, but the elephant impact on trees varies from one area to the next. This discrepancy indicates that these differences are due to the overall behavioural characteristics of the elephant. For example, elephant were introduced to the region recently and are still nervous with the effect that they congregate in areas of high tree density for protection. Other possible factors that could contribute to a non-homogeneous pattern of elephant impact on trees are also discussed.

Comparative use of burnt grassland by rare antelope species in a lowveld game ranch, South Africa
Gureja, N.Owen-Smith, N. .31-38

Abstract: The habitat selection and grazing preferences of ungulates before and after management burning in savanna grassland was investigated at Madrid Game Ranch near Klaserie. The antelope species observed included roan antelope (Hippotragus equinus), tsessebe (Damaliscus lunatus), Lichtenstein's hartebeest (Alcelaphus lichtensteini), and sable antelope (Hippotragus niger), with comparative observations made on zebra (Equus burchelli). Roan, tsessebe and zebra concentrated their grazing significantly within the burnt areas. Roan consistently cropped grasses at a higher level, favoured taller grass species and selected feeding sites with a denser canopy cover than the other ungulate species. Roan and hartebeest favoured bottomlands, while tsessebe, sable and zebra were relatively more commonly found in the midslope or upland region of the landscape. Accordingly there was some degree of ecological separation among these antelope species in terms of landscape regions favoured and grass species used, even within the burnt areas.

Diet of three courser species in an open grassland habitat, central South Africa
Kok, O.B.Kok, A.C. 39-42

Abstract: Analyses of the stomach contents of 76 double-banded coursers (Smutsornis africanus), 28 Burchell's coursers Cursorius rufus) and five Temminck's coursers (C. temminckii) collected at the Bloemfontein airport over a period of 13 years (1985–1997) showed the dietary composition of these closely related species to be remarkably similar. In all cases the coursers were found to be predominantly insectivorous. Isoptera, almost exclusively Hodotermes mossambicus workers, made up the bulk of the insect material. With regard to the double-banded courser, harvester termites were utilized throughout the year with little seasonal variation. Interspecific competition for food is probably limited by the nomadic way of life of these birds.

Avian pox in Swainson's francolin in South Africa
Van Niekerk, J.H.Verwoerd, D.J. 43-48

Abstract: Field trips were undertaken in South Africa from 1997–2001 to determine the prevalence of poxvirus infection in Swainson's francolin, Francolinus swainsonii. In total, 200 specimens were trapped or shot and examined for external lesions. Selected tissues from three dead specimens were removed for histopathological examination. Eighty-eight (44%) of 200 specimens revealed lesions, the highest compared to other wild bird populations. Other species such as ducks, doves, pigeons, helmeted guinea fowl (Numida meleagris) and other francolin species were also examined for similar lesions. Only one specimen (Coqui francolin, F. coqui) of 673 showed similar signs. This absence in other species suggests that Swainson's francolin can serve as an indicator species for certain poxviruses in a local or regional context. Swainson's francolin on the highveld showed a much higher prevalence of poxvirus infection than those in the bushveld. It is suggested that extreme cold conditions and lack of adequate food and cover during winter cause a stressful bottleneck. Swainson's francolin are dispersed in summer but converge in winter into groups, facilitating the spread of the virus between individuals.

Bird presence at Oribi Airport and recommendations to avoid bird strikes
Byron, J.Downs, C.T. 49-58

Abstract: Birds have been responsible for damage to aircraft and the subsequent loss of human life ever since the development of aviation. At Oribi Airport (Pietermaritzburg, KwaZulu-Natal), there is a higher incidence of bird strikes relative to other South African airports. Hadeda ibis (Bostrychia hagedash) and crowned plovers (Vanellus coronatus) are responsible for most bird strikes at Oribi Airport. During winter, the hadeda ibis was the most frequently seen bird (per hour) and used a predictable daily flight route beginning with movement to feeding grounds (SE–NW) around sunrise and returning (NW–SE) to a roosting site around sunset. Time of movement, with respect to season, varied according to sunrise or sunset flight time, i.e. in summer they moved earlier and returned later and vice versa. These bird flight patterns increased the probability of a strike with departing or arriving aircraft. During summer, there was a decrease in presence and use of Oribi Airport as a feeding ground for the hadeda ibis. Although the number of birds at the airport, particularly raptors, increased during the summer, few were present at any time. Recommendations for the prevention of bird strikes at Oribi Airport are presented.

Implications of the winter haulout for future survival and resighting probability of southern elephant seals at Marion Island
Pistorius, P.A.Kirkman, S.P.Bester, M.N.Taylor, F.E. 59-63

Abstract: Southern elephant seals haul out on land twice a year to moult and breed and the socio-ecological aspects of this behaviour have been well documented. A third haulout, which is referred to as the winter haulout, has received minimal attention and reasons for this haulout remain obscure. Here we estimated future survival and capture (resighting) probabilities of southern elephant seals that wintered at Marion Island during their first three years and compared these values to similar estimates from individuals that were not observed to winter over the same periods. We used longitudinal recapture data from the population and applied the program MARK to obtain these estimates. We found no significant differences in survival between wintering and non-wintering elephant seals. This suggests that survival is not a fitness correlate of this behaviour. However, seals of both sexes wintering at Marion Island in their first, and females wintering in their third year had significantly higher future capture probabilities relative to non-wintering seals. We thereby provide unique evidence of differential site fidelity within age- and sex classes, which has implications for population modelling.

A review of the successful eradication of feral cats from sub-Antarctic Marion Island, Southern Indian Ocean
Bester, M.N.Bloomer, J.P.Van Aarde, R.J.Erasmus, B.H.Van Rensburg, P.J.J.Skinner, J.D.Howell, P.G.Naude, T.W. 65-73

Abstract: This paper reviews the history of the feral cat eradication programme on sub-Antarctic Marion Island based on unpublished minutes of meetings, reports, letters, theses and published scientific papers; and reflects on the outcome of the eradication campaign. The 19-year programme comprised seven phases, commencing with a description of the effect of the cats on the Marion Island ecosystem, the characteristics of the cat population and the formulation of a management policy (phase 1: 1974–1976). Methods for control were selected and preparations were made for the implementation of the primary control measure, biological control with the feline panleucopaenia virus (phase 2: 1976/77). The virus was released in 1977 (phase 3: 1977), followed by the determination of its effects (phase 4:1977–1980). Monitoring of the effects of the virus continued, and the secondary control measure of hunting at night was tested (phase 5: 1981–1983). Full-scale implementation of hunting and continued monitoring of the effects of both the disease and hunting followed (phase 6: 1986–1989). The inclusion of intensive trapping and poisoning as tertiary control measures culminated in the final eradication of cats from Marion Island in 1991 (phase 7:1989–1993).

Seed dispersal by chacma baboons and syntopic ungulates in southern African savannas
Slater, K.Du Toit, J.T. 75-79

Abstract: The potential contributions made to seed dispersal by chacma baboons (Papio ursinus) and syntopic ungulates in the savanna biome of southern Africa were examined and compared. Simultaneous faecal collections were made from baboons and eland (Taurotragus oryx) in a rocky upland habitat and baboon and impala (Aepyceros melampus) in a bushveld lowland habitat in South Africa. At both sites the seed density was highest in baboon scats, although a significant difference was found only between eland and baboons. A difference in size-classes of seeds dispersed in faeces by baboons, eland and impala was also found. No significant differences were found in the number of germinated grasses, forbs or woody plant species between baboon and ungulate samples from either site. Although they may not be more important seed dispersers than syntopic ungulates (in quantitative terms), baboons potentially disperse different species of seeds and are also better able to disperse seeds across fence lines.

Space use by a reintroduced serval in Mount Currie Nature Reserve
Perrin, M.R. 79-86

Abstract: There are few quantified observations of carnivores reintroduced into the wild. However, such observations are important in order to develop a better understanding of the feasibility of reintroductions. In this study radiotelemetry was used to study the movements of young servals reintroduced into a nature reserve in the midlands of KwaZulu-Natal, South Africa. Of the two introduced servals, a female left the reserve, which contained a high prey density of rodents, to establish the core of her home range in intensively used farmland. The servals (a male and a female) showed significantly more locomotory activity at night than during the day, and preferred riverine and vlei habitats to grassland. Estimates of home range size varied from 2.99 km² (minimum convex polygon), to 6.27 km² (bivariate ellipse), to 9.35 km² (harmonic mean), according to the method of data analysis. After a second relocation, the female returned to an area of rural human settlement, which suggested some degree of habituation. It was able to survive natural environmental conditions, forage for food, and establish regular activity and space use patterns. The consequences for future reintroduction attempts are discussed.

Distribution, movement, and estimated population size of killer whales at Marion Island, December 2000
Pistorius, P.A.Taylor, F.E.Louw, C.Hanise, B.Bester, M.N.De Wet, C.Du Plooy, A.Green, N.Klasen, S.Podile, S.Schoeman, J. 86-92

Abstract: We report here on some shore-based killer whale observations that were collected at several localities around Marion Island (46º54'S; 37º45'E) in a single day during their peak activity period around the island. Using island wide observational data we mapped the movement patterns of killer whales, which were restricted to the east coast and may be related to breeding and moulting aggregations of southern elephant seals found there. We estimated the killer whale population at Marion Island to be in the range of 25–30 individuals. Movement of individually identified pods between adjacent observation points suggested estimated swimming speeds of between 11.9 km/h and 14.44 km/h while patrolling along the Marion Island beaches. No diel activity pattern was evident. We stress the need for more data similar to that obtained in the present study in order to render observations and monitoring of killer whales from a single point on the island meaningful.