THE RELATIONSHIP BETWEEN RAINFALL, LION PREDATION AND POPULATION TRENDS IN AFRICAN HERBIVORES

The relationship between rainfall, lion predation and population trends in African herbivores, with special emphasis on buffalo, wildebeest and zebra, was studied in the central district of the Kruger National Park between 1968 and 1992. The study commenced at the end of a dry cycle, and moved into a 10-year wet cycle that was followed by another 10-year dry cycle. Populations of the herbivores reacted differently to these cycles: those of wildebeest and zebra fluctuated inversely with rainfall, whereas those of buffalo and the other herbivores fluctuated directly with rainfall to a greater or lesser degree. The proportions in which some species were represented in lion kill samples followed a similar trend, with wildebeest and zebra being more vulnerable in the wet cycle and buffalo and waterbuck being more vulnerable in the dry cycle. Simulations of the buffalo, wildebeest and zebra populations suggest that buffalo are more heavily influenced by predation during population declines than are the other two species, followed by wildebeest, with zebra experiencing the smallest influence. The driving force in the ecosystem, however, appeared to be rainfall.