ORIGINAL PAPER Charlene Bissett & Ric T. F. Bernard & Daniel M. Parker Received: 25 August 2011 / Accepted: 18 December 2011 / Published online: 15 January 2012 # Mammal Research Institute, Polish Academy of Sciences, Białowieża, Poland 2012 Abstract Large mammalian carnivores place significant pressure on their prey populations and this is exacerbated within the fenced reserves of Africa. However, foraging theory predicts that diet switching by predators may mitigate this pressure. In this study, we use data collected between 2003 and 2007 from an enclosed system in the Eastern Cape Province of South Africa to examine the response of lions Panthera leo to changes in the abundance of two important prey species — kudu Tragelaphus strepsiceros and warthog Phacochoerus africanus. As the relative abundance of war- thogs increased, the number of kudu kills decreased signif- icantly, whereas warthog kills became significantly more frequent. A similar pattern was observed for lion prey pref- erence and the switch from kudu to warthog was also reflected in a significant decrease in the mean prey mass. Our results suggest that a diet shift occurs in lions and that the change in diet is primarily in response to an increase in warthog numbers. Prey switching may promote the persis- tence of predator–prey systems, which is particularly impor- tant for fenced systems where natural immigration of prey is not possible. However, continued collection and analysis of long-term observational data from the multipredator, multi- prey systems of Africa is required to facilitate a full under- standing of predator–prey dynamics. Keywords Diet switching . Large predators . Predator–prey interaction . Prey preferences Introduction The diet of predators in multiple prey species systems is affected by a range of factors including abundance of different prey species and their vulnerability, anti-predator behavior and defence, age and sex, and the presence of and interference from other predators (Perry and Pianka 1997; Garrott et al. 2007). Vulnerability is not solely a species-specific character- istic and will vary with body condition and therefore with age, reproductive status and environmental factors such as drought (Owen-Smith and Mills 2008). Thus diet can vary in space and time. The optimal foraging theory (MacArthur and Pianka 1966) provides a theoretical framework against which feeding behavior can be understood and predicts that the diet of predators, such as lions Panthera leo, will vary as the relative abundance of one or more of a range of alternative prey species varies (Pyke et al. 1977). This dietary variation may be sea- sonal as in some mustelids (Carss et al. 1998; Begg et al. 2003) and Geoffroy’ s cat Leopardus geoffroyi (Canepuccia et al. 2007), where seasonal climate variation drives seasonal changes in food abundance. Alternatively, it may coincide with longer population cycles such as that of the snowshoe hare Lepus americanus where lynx Lynx canadensis switch to preying on red squirrels Tamiasciurus hudsonicus during peri- ods of least hare abundance (O’Donoghue et al. 1998). Finally, it may be driven by longer cycles of climate change, such as drought, where one species may be more susceptible to drought than others and that species then becomes more vul- nerable (Owen-Smith and Mills 2008). The influence of generalist mammalian predators on prey population dynamics has been well studied (Korpimäki and Communicated by: Dries Kuiper C. Bissett : R. T. F. Bernard : D. M. Parker Wildlife and Reserve Management Research Group, Department of Zoology and Entomology, Rhodes University, Grahamstown 6139, South Africa C. Bissett (*) Kwandwe Private Game Reserve, Grahamstown 6139, South Africa e-mail: c.bissett@ru.ac.za Acta Theriol (2012) 57:225–231 DOI 10.1007/s13364-011-0071-8 The response of lions (Panthera leo) to changes in prey abundance on an enclosed reserve in South Africa