Populations of small prey species (< 92 kg) can be regulated by competition, habitat-mediated responses, climate change, disease and predation. Populations of small prey species have declined in the Addo Elephant National Park Main Camp Section since the reintroduction of apex predators (lion and spotted hyaena). One possible explanation is predation by lion and spotted hyaena. However, small prey species are not generally considered preferred prey items of these predators, hence their contribution to predator diets needs to be explored. Global Positioning System (GPS) cluster analysis has emerged as a viable approach to locate lion kills for lion diet estimation in AENP, however this technique is known to bias diet estimates to large prey species. Understanding the impact of lion predation on populations of small prey in Main Camp therefore requires better estimates of lion diets. This study investigated the potential underestimation of small prey species in lion diet estimates by combining the data from scat analysis and carcasses located at GPS clusters. The adjusted lion diets were then used to investigate if the impact of lion predation could explain declines in small prey, by relating lion prey preferences to prey population trends in Nyathi. Using the results from Nyathi, it could then be inferred whether lions could have been responsible for the declines observed in Main Camp. Six GPS-collared lions provided location data used to construct individual movement paths, along which spatio-temporal clusters of GPS locations (n = 4896) were identified for ground investigation. Carcasses (n = 643) were recorded at the GPS clusters and scats (n = 256) were collected at GPS clusters with or without carcasses. Data from the located carcasses and scat collections were then used to create a history of feeding events for each collared lion in Main Camp-Colchester and Nyathi from a) carcasses alone or b) a combination of scats and carcasses, based on an estimated short and long lion throughout period. Relative prey availability was estimated based on camera trapping in Nyathi in high lion, low lion and no lion use areas, as lions may encounter some prey species more than other prey species. Jacobs’ index prey preference was used to investigate the importance of prey species to lion diets at three landscape scales: 1) Nyathi, 2) lion UD and 3) core lion UD. Lastly, prey population trends were investigated in Nyathi to provide an indication of possible changes in prey populations. Large prey species dominated the adjusted diets of lions in Main Camp-Colchester and Nyathi. However, when comparing the GPS carcass-derived lion diet estimate to the combined lion diet estimate, small prey were underestimated more often than large prey in the GPS carcass-derived lion diet estimate. Missed feeding events were therefore a function of prey body size. In addition, missed feeding events were also representative of the lion diets based on carcasses, with the tendency for species more often consumed to be missed more often in the diet record. However, even though small prey species were underestimated, they represented the minority of species consumed by lions and were predominantly avoided by lions in Nyathi. Lion prey preferences thus did not correlate to the declines in small prey species in Naythi, suggesting other potential drivers are important for small population trends in Nyathi. Lion predation cannot be ruled out as a driver of the decline in small prey species in Main Camp, due to different ecological conditions (e.g. vegetation density) in Main Camp compared to Nyathi, during the observed small prey population declines. Lion prey preferences in Nyathi revealed fine-scale variations in species specific preferences by lions, as well as site-specific differences in prey preferences when compared to published lion prey preference meta-analyses. These findings suggest that metaanalysis studies should be used as a guideline from which hypotheses about local predatorprey interactions can be developed rather than as an absolute measure of prey preference.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nmmu/vital:27542 |
| Date | January 2017 |
| Creators | Gerber, Amarein Judith |
| Publisher | Nelson Mandela Metropolitan University, Faculty of Science |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis, Masters, MSc |
| Format | vi, 114 leaves, pdf |
| Rights | Nelson Mandela Metropolitan University |
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