The impact of lion predation on the large ungulates of the Associated Private Nature Reserves, South Africa

Abstract

A predator-prey study was undertaken to determine the impact of lion Panthera leo predation on the declining populations of large ungulates in the Associated Private Nature Reserves, an open system with the Kruger National Park. The determination of prey population trends and their spatial distribution in relation to predator habitats are fundamental to studying predator-prey relationships. A combination of aerial counting and road strip censusing techniques were used to determine the prey population trends in the Associated Private Nature Reserves. The age and sex structure, habitat selection and seasonal abundance of the most abundant lion prey in the study area were compared with that of ungulate populations elsewhere in African savannas. The population dynamics of the lions in the Associated Private Nature Reserves were investigated by using the call-in counting technique. The total number of lions, mean pride size, lion density, and the age and sex structure of the lions in the study area was compared with that of lions in other African savanna woodland habitats. The range dynamics and habitat selection of four focal lion groups in the Associated Private Nature Reserves were studied. An adult lioness from each of the C, S and M prides, and an adult male from the N coalition were immobilized and then fitted with radio-collars. The range use and habitat selection of the lions in the present study were compared with that of their preferred prey, and with that of lions in other African savannas. In African savanna ecosystems, rainfall is regarded as the key component driving the system. Ecological modelling was therefore used to better understand the interrelationship between rainfall, prey population trends and lion predation in the Associated Private Nature Reserves. The overall conclusions of the ecological modelling were then compared with the results of the present study on lion predation in the Associated Private Nature Reserves. The predation rate and prey selection of the lions in the Associated Private Nature Reserves was determined by using a combination of short-term continual predation observations and historical lion kill data. The prey selection of the lions in the present study was compared with that of historical lion kill data to determine whether the predation pressure shifted from the preferred blue wildebeest and Burchell’s zebra to the more abundant impala, and the larger buffalo and giraffe. The killing and consumption rates of the focal lion groups in the present study were used to determine the impact of lion predation on the large ungulate populations in the Associated Private Nature Reserves. Lion predation data for the present study were compared with that of lions in other African savannas. The results of the present study were used to test the hypothesis that the apparent decrease in the large ungulate populations in the Associated Private Nature Reserves from 1980 to 2003 was due to a combination of lion predation, climatic fluctuation, the change in habitat over time, the removal of the boundary fences between the Associated Private Nature Reserves and the Kruger National Park, and the change in the aerial counting method from 1992 to 1996.