Context Habitat loss and alteration affect wildlife populations worldwide. Bush encroachment alters landscapes and threatens arid and semi-arid grasslands, but its effects on predator–prey relationships and carnivore community ecology are not well understood. Predation strategies of large predators, for example high-speed pursuits versus ambush from short distances, are likely to be affected differently by bush encroachment. Objectives We assessed how bush encroachment affects overall predation success of cheetahs (Acinonyx jubatus) and leopards (Panthera pardus) in a savanna landscape under variable fractional woody cover (FWC). We tested if predation success remained relatively unchanged for leopards across a gradient of FWC, and whether cheetah predation was most successful at low to intermediate cover and varied seasonally. Methods Belly scores of predators were measured from camera-trap images collected over 7 years in north-central Namibia and used to index predation success. We derived predicted belly score probabilities as a function of FWC, which was measured using a Synthetic Aperture Radar (SAR)-derived satellite data layer. Results Predicted leopard predation success was highest at 0.27–0.34 FWC in the dry season, potentially due to lower prey density in highly covered areas and decreased prey catchability in low cover. Predicted cheetah predation success was highest at 0.24–0.28 FWC in the wet season, potentially due to increased landscape openness, high availability of habitat margins for visualising and stalking prey, and decreased kleptoparasitism by leopards. These results highlight optimal habitat cover thresholds that favour lower FWC for cheetah than for leopard. Conclusions The findings indicate that landscape heterogeneity is important for predation success of cheetahs and leopards, suggesting that habitat management should focus on bush control efforts to maintain intermediate levels of bush cover.
Bush encroachment is a habitat change phenomenon that threatens savanna and grassland ecosystems worldwide. In Africa, large carnivores in bush encroached landscapes must adjust to increasing woody plant cover and biomass, which could affect predation success at multiple stages through complex and context-dependent pathways. We highlight, interpret, and compare studies that assessed how bush encroachment or related habitat parameters affect the predation stages of large African carnivores. Bush encroachment may directly or indirectly affect predation success in various ways, including by: (1) altering habitat structure, which may affect hunting efficiency and prey accessibility; (2) changing prey abundance/distribution, with smaller species and browsers being potentially favoured; (3) influencing interference competition within the carnivore guild. For habitat or dietary specialists, and subordinate predators that are vulnerable to both top-down and bottom-up ecosystem effects, these alterations may be detrimental and eventually incur population fitness costs. As the threat of bush encroachment continues, future studies are required to assess indirect effects on competitive interactions within the large African carnivore guild to ensure that conservation efforts are focused. Additionally, to better understand the effects of bush encroachment across Africa, further research is necessary in affected areas as overall little attention has been devoted to the topic.
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