406 P. Strampelli et al.


country based on a mean density of 0.10/km2 (10 leopards/ 100 km2). This estimate has been widely criticized because the model omitted important factors such as anthropogenic mortality and prey availability and assumed that leopards occur at maximum potential densities in all available habi- tats (Jackson, 1989; Balme et al., 2010). Nevertheless, it formed the basis of the most recent increase in the trophy hunting quota, mainly because alternative estimates of population densities are not available (CITES, 2007). A more accurate assessment of leopard populations in Mozambique is needed to determine the reliability of the methods currently employed to set the hunting quota, and to ensure that future changes are based on robust data. Here we use closed-population spatially explicit capture–


recapture methodology to estimate the density of leopards in Xonghile Game ReserveinsouthernMozambique. The aimof the study was to obtain the first empirical density esti- mate for a leopard population in southern Mozambique and present information to guidemanagement and provide a base- line for the assessment of conservation interventions, and to explore the implications of our findings for trophy hunting.


Study area


Xonghile Game Reserve (Fig. 1)isa 450 km2, unfenced, le- gally protected area in southern Mozambique. Its northern border is c. 13 km south of Limpopo National Park, the country’s largest national park. It borders South Africa’s Kruger National Park to the west and unprotected land to the north, east and south, and is part of the Greater Limpopo Transfrontier Conservation Area, a transbound- ary initiative linking protected parks and reserves in Mozambique, South Africa and Zimbabwe via non- protected areas. The predominant habitat in the Reserve consists of sand plains (sandveld) characterized by low woodlands and thickets on deep sandy soils, and short-grass pans (seasonally flooded depressions). Although popula- tions of large mammals in the region were severely depleted during the 1964–1992 armed conflicts (Hanks, 2000), the progressive removal of fencing along the border of Kruger National Park since 2005 has provided opportunities for wildlife to move into the area. No human population per- manently resides in the Reserve, with the main anthropo- genic impacts coming from relatively low levels of poaching for bushmeat, anti-poaching efforts, and lowlevels of tourism (LA & KTE, unpubl. data). Trophy hunting does not currently take place in the Reserve.


Methods


Camera trapping Twenty-nine digital motion-activated cameras of various models (HC500, Reconyx, Holmen, USA; Tiny W-2, Spy


Density estimation


Densitywasmodelled in a spatially explicit capture–recapture framework, using the package secr (Efford, 2015)in Rv. 3.2.3 (R Development Core Team, 2015). Amaximum-likelihood framework was chosen over a Bayesian one to make results comparable with other studies (Noss et al., 2013; Tobler & Powell, 2013) and because computation times are shorter (Efford, 2015). Leopards were identified from their pelage patterns and


sexed by visual inspection of external genitalia. We chose the flank with the greater number of captures (left) for iden- tification of individual leopards. Individual spatial capture and trap effort histories were developed following recom- mended procedures (Efford, 2015), with each day (24 hours) treated as a separate sampling occasion (Goldberg et al., 2015). Information on varying effort from different camera stations (the number of days each camera was ac- tive) was included to improve estimates of detection prob- ability. We increased the buffer width around the trapping grid until density estimates stabilized, ensuring that no indi- vidual outside the buffer area could be captured, and fitted a half-normal detection function to the distance between the centre of the home range and the camera station. This is the most commonly used function in spatial capture–recapture analyses (Efford, 2004; Boron et al., 2016) and describes the probability of capture (P) of an individual i at a trap j as a function of distance d from the activity centre of the individ- ual to the trap, as follows: Pij = g0 exp (-dij2/(2σ2), where g0 is the probability of capture at the exact centre of the home range, and σ is a spatial parameter related to home range size


Oryx, 2020, 54(3), 405–411 © 2018 Fauna & Flora International doi:10.1017/S0030605318000121


Point, Victoriaville, Canada; Trophy Cam, Bushnell, Overland Park, USA) were deployed at 26 stations over c. 300 km2 in the Xonghile Game Reserve (Fig. 1) during 24 August–23 November 2012. Twenty-three stations were equipped with a single camera and three stations with two cameras each. The majority of stations (23)were located 0.5–3km apart,


ensuring that multiple cameras were likely to be present in an individual leopard’s home range. Three stations were placed 5–6 km from the nearest station. There was therefore a possibility that an individual’s home range did not contain a station, but this is unlikely given the low prey densities in the study area (LA & KTE, unpubl. data), and spatially explicit capture–recapture models allow for the presence of such gaps in the trap array when estimating density (Borchers & Efford, 2008). Cameras were set on trees along roads and game trails at a height of 35 cm. The sur- vey duration was 92 days, which was considered adequate for assuming demographic closure and is consistent with previous studies of large felids (Karanth, 1995;Alexander et al., 2015; Boron et al., 2016).


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