Big cats at large: Density, structure, and spatio‐temporal patterns of a leopard population free of anthropogenic mortality

Abstract

Human impact is near pervasive across the planet and studies of wildlife populations free of anthropogenic mortality are increasingly scarce. This is particularly true for large carnivores that often compete with and, in turn, are killed by humans. Accordingly, the densities at which carnivore populations occur naturally, and their role in shaping and/or being shaped by natural processes, are frequently unknown. We undertook a camera-trap survey in the Sabi Sand Game Reserve (SSGR), South Africa, to examine the density, structure and spatio-temporal patterns of a leopard Panthera pardus population largely unaffected by anthropogenic mortality. Estimated population density based on spatial capture-recapture models was 11.8 ± 2.6 leopards/100 km 2 . This is likely close to the upper density limit attainable by leopards, and can be attributed to high levels of protection (particularly, an absence of detrimental edge effects) and optimal habitat (in terms of prey availability and cover for hunting) within the SSGR. Although our spatio-temporal analyses indicated that leopard space use was modulated primarily by "bottom-up" forces, the population appeared to be self-regulating and at a threshold that is unlikely to change, irrespective of increases in prey abundance. Our study provides unique insight into a naturally-functioning carnivore population at its ecological carrying capacity. Such insight can potentially be used to assess the health of other leopard populations, inform conservation targets, and anticipate the outcomes of population recovery attempts. K E Y W O R D Scarnivore ecology, carrying capacity, Panthera pardus, population regulation, spatial capture-recapture

Ecological opportunity drives individual dietary specialization in leopards

“…Although our results suggested that prey density and vulnerability at the home range scale (i.e. per capita resource availability) did not affect the magnitude of dietary specialization exhibited by individuals, intraspecific competition, possibly for space and mates more than food (Balme, Rogan, et al, ), still likely contributed to some individuals specializing. The high density of leopards in the SSGR is unusual; most leopard populations, even those in comparable savanna habitats, are depressed by anthropogenic perturbation (Balme, Rogan, et al, ).…”

“…Most extant indigenous mammal species are present on the reserve, including the entire large carnivore guild, as well as their primary prey base (Radloff & Du Toit, ). Estimated leopard population density, based on spatial capture–recapture modelling, is 11.8 ± 2.6 leopards/100 km 2 and close to capacity (Balme, Rogan, et al, ).…”

“…per capita resource availability) did not affect the magnitude of dietary specialization exhibited by individuals, intraspecific competition, possibly for space and mates more than food (Balme, Rogan, et al, ), still likely contributed to some individuals specializing. The high density of leopards in the SSGR is unusual; most leopard populations, even those in comparable savanna habitats, are depressed by anthropogenic perturbation (Balme, Rogan, et al, ). An interesting next step would be to evaluate levels of niche variation along a gradient of leopard population density to further examine how intraspecific competition shapes patterns of individual specialization.…”

“…in arid or montane habitats) are likely to display less niche variation than those occupying heterogeneous savanna habitats, such as found in the SSGR. Another factor predisposing individual specialization in our focal population was the fact that it was at or near to its ecological carrying capacity (Balme, Rogan, et al, ). Newsome et al () found a higher prevalence of dietary specialization in sea otter populations that were close to capacity compared to those well below capacity, likely due to increased competition for resources in high‐density populations.…”

“…Clients are taken on two ‘game drives’ daily (ca. 06:00–09:30 and 15:30–19:00, including after dark with a spotlight), which are led by an experienced guide and coincide with leopard activity peaks (Balme, Rogan, et al, ). On average, 98 ± 2 vehicles are active throughout the SSGR per game drive, resulting in a mean density of 1 vehicle per 6 km 2 .…”