522 M. A. Vinks et al. Survival rates and detection probabilities
Three Cormack–Jolly–Seber models were identified as the best-supported models of leopard survival (Table 2), and these models suggested that both detection (P) and apparent survival (w) varied by sex. However, the model-averaged es- timate of apparent survival for females (0.73, 95%CI 0.56– 0.85) was similar to that of males (0.74, 95%CI 0.56–0.87). The probability of detection was relatively low, with model- averaged estimates of 0.35 (95%CI 0.24–0.48) for females and 0.33 (95%CI 0.22–0.47) for males.
Population density
FIG. 3 Total number of (a) unique leopards captured, and (b) all leopard detections at each camera-trap site overlain on the gradient of space use (kernel utilization distribution, KUD) for two locally resident (and closely monitored) African lion Panthera leo prides (data from Vinks et al., 2021). Lion kernel utilization distribution values of 1–5 represent low–high space use and the 60% isopleth was derived from this gradient. Leopard space use appeared to overlap lion space use, suggesting that leopards are not strongly limited by interspecific competition.
densities for our camera-trap grid were then compared with leopard detections.
Results
Leopard population structure From 4,200 camera-trap days we recorded 101 leopard detec- tions and identified 29 individuals (17 females, 9 males and 3 unknown) during 2013–2019. The number of leopard detec- tions at each sitewas 1–24 (mean 6.7,median 4)and leopards were detected at all 15 sites (Figs 2&3). Each site detected 1–9 (mean 3.3) individuals, with the majority of individuals at the northern-most site (Figs 2&3). Throughout the course of the studywe detected a mean of 9 (range 7–12) leopards annually (Table 1). The sex ratio for 26 individuals incorporated in the survival analysis was 1 male:1.89 females.
We detected 12 individual leopards in 20 total detections in 2016, nine of which (69%) were known previous to the study. In addition, we detected one dependent cub, which we excluded from the abundance estimate. The estimat- ed population size in 2016 was 18 (95%CI 12–33). The HMMDM and MMDM between detections for 11 leopards recaptured atmultiple sites (2013–2019) were 2.69 km(range: 1.2–5.7 km) and 5.38 (range: 2.4–11.4 km),
respectively.Apply- ing these buffers to the camera-trap locations yields a sam- pling area of 228 km2 and 538 km2 centred along the Lufupa river (Fig. 1). These estimates of population size and sampling area yield a density of 7.89 leopards per 100km2 (95%CI 6.14– 14.47 leopards per 100 km2)and 3.34 leopards per 100 km2 (95%CI 2.23–6.13 leopards per 100 km2), respectively.
Discussion
Leopard population density or demography are rarely eval- uated in large African protected areas of high conservation concern (Balme et al., 2014). Improving our understanding of the effects of anthropogenic pressures on leopard popula- tions is a critical first step for leopard conservation. In the Greater Kafue Ecosystem, recent research has shown that ungulate prey density is considerably lower than expected for an ecosystem with its vegetation type and rainfall (Vinks et al., 2020), and low prey density leads to a logical expectation of low carnivore density, and, if severe, lower adult survival (Van Orsdol et al., 1985; Stander et al., 1997; Eberhardt, 2002). Moreover, reductions in density have been particularly great for large prey species that were pre- viously preferred by lions, squeezing the entire carnivore guild into a narrow dietary niche centred on the species preferred by leopards (Creel et al., 2018). Consequently, we would expect that increased interspecific competition with- in the carnivore guild could exacerbate the effects of prey depletion. On the other hand, the densities of dominant competitors within this guild (lions and spotted hyenas Crocuta crocuta) correlate with the density of prey, both within and between ecosystems (Schaller, 1972;Van Orsdol et al., 1985; Hofer&East, 1995). Thus, the direct effect
Oryx, 2022, 56(4), 518–527 © The Author(s), 2021. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605321000223
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