No abstract

South Africa's National Parks Board has opted to control African elephants (Loxodonta africana) through culling in the Kruger National Park (KNP). Killing elephants is highly controversial. The Board must balance this controversy against the probable destruction of vegetation and the consequent depletion of biological diversity that high elephant densities cause. Annual aerial counts provided the population estimates on which the culling quotas were based. For management purposes, the elephant population of the Park is divided into four sub-populations. From 1984 to 1994, the annual quota was usually taken from only one of these sub-populations during a given year. This resulted in 3 to 5 years elapsing between culls in each sub-population. We investigated the year-toyear changes in densities after culling. These changes were density dependent. Density dependence implies that immediate culls following estimated high densities may be premature. If left alone, the densities would decline naturally. Indeed, culling becomes self-reinforcing as it moves population densities towards the level where reproduction is greatest. Data confirm this intuition: at densities greater than 0.37 elephants/km 2 elephant numbers generally declined without culling. Many culls were unnecessary. Culling, as implemented in the past, may have had consequences for elephants and their habitat that were different to those expected from a mere reduction in their numbers. Densities in the year immediately after a cull tended to decline -not increase as would be expected from density dependence alone. Undoubtedly, this unexpected decline was the consequence of disturbance and subsequent emigration. In following years, the densities rose as animals moved back into the sub-population. A management programme where culling will be instituted only when densities exceed 0.37 elephants/km 2 in selected regions in the park for at least 1 year, may be more acceptable than the programme used up to 1995. However, we do not know if the vegetation of KNP can withstand the resulting episodic high densities. With densities presently exceeding the cut-off values calculated for both the south and the northern management regions vegetation changes there need to be monitored.

Large herbivores such as elephants (Loxodonta africana) apparently have a negative impact on woody vegetation at moderate to high population densities. The confounding effects that fire, drought, and management history have may complicate assignment of such impacts to herbivory. We reviewed 238 studies published over 45 years and conducted a meta‐analysis based on 21 studies that provided sufficient information on response of woody vegetation to elephants. We considered size and duration of studies, elephant densities, rainfall, fences, and study outcomes in our analysis. We detected a disproportionate citation of 20 published studies in our database, 15 of which concluded that woody vegetation responded negatively to elephants. Our analysis showed that high elephant densities had a negative effect on woody vegetation but that rainfall and presence of fences influenced these effects. In arid savannas, woody vegetation always responded negatively to elephants. In transitional savannas, an increase in elephant densities did not influence woody vegetation response. In mesic savannas, negative responses of woody vegetation increased when elephants occurred at higher densities, whereas elephants confined by fences also had more negative effects on woody plants than elephants that were not confined. Our analysis suggested that rainfall and fences influenced elephant density related impact and that research results were often site‐specific. Local environmental conditions and site‐specific objectives should be considered when developing management actions to curb elephant impacts on woody vegetation.

Landscape heterogeneity may influence ranging behaviour of mammals. Here we relate the home range size of elephants living in the Kruger National Park to the number of patches, proportion of each patch, spatial arrangement of patches, patch shape, and contrast between neighbouring patches. Home range sizes decreased exponentially with an increase in the number of patches per 100 km 2 and the home range sizes of bulls were in general more strongly related to measures of heterogeneity. This may reflect differences in perception of heterogeneity between the sexes.Key words: FRAGSTATS, home range, landscape heterogeneity RésuméIl se peut que la hétérogénéité du paysage agisse sur le comportement des mammifères au pâturage. Dans cette étude nous associons la taille des domaines vitaux des éléphants résidant dans le Parc National de Kruger au nombre de parcelles et leurs dimensions, disposition spatiale et forme, ainsi que le contraste entre des parcelles avoisinantes. La taille des domaines vitaux diminua exponentiellement avec l'augmentation dans le nombre de parcelles par 100 km 2 alors que les domaines vitaux des mâles furent plus fortement associés aux mesures d'hét-érogénéité en général. Cela est peut être dû aux différences au niveau de la perception d'hétérogénéité entre les sexes.

Translocations are increasingly important tools for endangered species conservation, but their success is often uncertain. We analyzed 125 time series of grazing mammal translocations in South African protected areas. Some 94% of translocations succeeded (66% unambiguously) even though most populations began with <15 individuals and most of the species involved are of conservation concern. Adding new individuals to existing small populations increases per capita growth rates and seems to prevent translocations from failing. Growth of the translocated populations is both greater and less variable than wild mammal populations and appears less affected by the typically important ecological factors (e.g., initial propagule size, precipitation, reserve size, or presence within historical range). One-third of the populations showed robust signs of density dependence but we detect few examples of Allee effects. Our results, from empirical time series of small populations, offer new insights into achieving success for translocation programs limited to releasing few individuals.