408 P. Strampelli et al.
TABLE 1 Model selection parameters for spatially explicit capture–recapture models in R package secr. Model
Description secr.0
secr.sex.σ
secr.sex.g0
secr.sex
No variation between sexes σ4 varies between sexes g05 varies between sexes g0 and σ vary between sexes
1Akaike Information Criterion, adjusted for small sample size. 2Difference from best ranking (lowest AIC) model. 3Number of model parameters. 4Spatial parameter related to home range size. 5Probability of capture at the home range centre.
frequencieswere 9, 3, 2, 2 and 1 for the five males; 6 and 4 for the two females; and 3 and 1 for the two unsexed individuals.
Density estimation
The bestmodel (AICc = 360.36) did not allow g0 or σ to vary with sex (secr.0),andreceivedsignificantlymore support than the next best alternative (
secr.sex.σ, ΔAICc = 10.47; Table 1). The leopard density estimate of the best-fitted model
(secr.0)was 2.60 ± SE 0.96 adults/100 km2. Capture prob- ability at the centre of the home range (g0) was estimated to be 0.043 ± SE 0.013, and the spatial parameter (σ)to be 1,936 ± SE 279 m(Table 2). Buffer width stabilized at 10,000 m, as reported by similar leopard density studies (Gray & Prum, 2012; Borah et al., 2013).
Discussion
Leopard density Our study provides a baseline leopard density estimate for a relatively well-protected area and the first empirical estimate for a leopard population in Mozambique. Usingspatially explicit capture–recapturemodelswe estimated leopard density in the Xonghile Game Reserve to be 2.60 ± SE 0.96 adults/100 km2. Although this is low com- pared to studies elsewhere in sub-Saharan Africa, it is higher than estimates from other protected areas in southern Africa: 0.60 leopards/100 km2 in the dry savannahs of the Kalahari Gemsbok National Park (South Africa; Bothma & Le Riche, 1984), 0.62/100 km2 in the savannah/woodland Cederberg Wilderness Area (South Africa; Martins & Harris, 2013) and 1.50/100 km2 in the savannah habitat of the Kaudom Game Reserve, Namibia (Stander et al., 1997). In South Africa’s Kruger National Park, contiguous
with the Reserve’s western border, high leopard densities of 30.3/100km2were reported for the Sabie riverine area (Bailey, 1993), and 12.7/100km2 in theN’wantesi concession (Maputla et al., 2013).We believe the observed differences are probably a reflection of different habitats, and consequently prey avail- ability, between sites.Whereas density estimates fromKruger
TABLE 2 Parameters and density estimated by the best model (secr.0).
Parameter1 g0
σ (m) Leopards/100 km2 Mean ± SE
0.043 ± 0.013 1963 ± 279
2.599 ± 0.957 95% CI
0.024–0.078 1464–2562 1.292–5.231
1g0, probability of capture at the home range centre; σ, spatial parameter related to home range size.
National Park came from highly productive riverine forests (Bailey, 1993) and savannah woodlands (Maputla et al., 2013), Xonghile Game Reserve predominantly comprises nutrient-poor, lower-productivity sandveld,which sustains lower animal densities (Redfern et al., 2003; Scholes et al., 2003). The relatively high level of protection in the Reserve (LA&KTE, unpubl. data) suggests that the lowprey densities are not a result of human hunting activities. Nonetheless, the Reserve could be acting as a population
sink for leopards dispersing from Kruger National Park, through anthropogenic mortalities occurring in the adjacent non-protected areas. Estimates for anthropogenic leopard mortalities in the area are not available, but it is possible that individuals venturing into the non-protected areas adjoining the Reserve could be suffering relatively high anthropogenic mortality rates,whichcouldlower populationdensities and at- tract leopards from surrounding areas (e.g. Kruger National Park). This vacuumeffect has been documented for large car- nivores and leopards in particular, and it may cause edge ef- fects that affect the interior of even large protected areas (Loveridge et al., 2007). Longer term camera trapping or track- ing using collars equipped with global positioning system units, combined with social surveys targeting the communities outside the Reserve, are necessary to ascertain whether this af- fects leopards in and around Xonghile Game Reserve.
Methodological considerations and sex-specific parameters
The majority of our stations had only one camera trap, ra- ther than the recommended two-camera set-up (one for
Oryx, 2020, 54(3), 405–411 © 2018 Fauna & Flora International doi:10.1017/S0030605318000121 AICc1
360.364 370.835 371.280 394.663
ΔAICc2 0.000
10.471 10.916 34.299
AIC model weights
1 0 0 0
Model
K3 4
5 5 6
deviances 324.364
322.663 323.281 322.835
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