Fosas in Madagascar’s deciduous forests 831


confirmed by a local guide and categorized as Madagascar National Park trail, local (actively used by local people), disused-local (formerly used by local people), game (animal trail), logging (actively used by loggers), or disused-logging (formerly used by loggers). We used QGIS v. 2.12.1 (QGIS Development Team, 2015)


and FRAGSTATS v. 4.2 (McGarigal et al., 2002) to create 12 landscape-level covariates, to examine the effects of human settlement, landscape degradation, and ecological variables on fosa occupancy (Table 1). A 500-m buffer was created around each camera-trap station and the mean value of the raster cells was calculated for each covariate. Two metrics were used to measure forest cover: global


forest cover (GFC; Hansen et al., 2013) and mean vegetation continuous field (VCF; DiMiceli et al., 2011). The per cent of GFC (which is at 30 m resolution) that can be classified as forest may be specified. We chose 10, 20, 30 and 50% and compared these within univariate models to find the best predictor of fosa occupancy. VCF provides a forest cover per cent at 250 m map resolution. Maps of GFC for Andranomena Special Reserve were unavailable for the- survey year, and therefore the most recently available (2014) maps were used. Four measures of fragmentation (Table 1; Gerber et al., 2012a; Farris et al., 2015b) were calculated with FRAGSTATS. Two measures of water proximity were calculated using


a waterway raster containing Madagascar’s major water sources (Mapcruzin, 2016) and a digital elevation model (Jarvis et al., 2008), facilitating the mapping of low-elevation areas that may represent drainage points and potential sea- sonal streams. The covariate mean elevation was created from the Shuttle Radar Topography Mission’s 90 m raster (Carroll et al., 2009). We used the Rv. 3.3.3 (R Core Team, 2017) package unmarked v. 0.11–0 (Fiske & Chandler, 2011) to run single- species, single-season occupancy modelling of the fosa, cat, and dog. Prior to modelling, a Pearson’s correlation test was used to eliminate multicollinearity. We removed correlated continuous predictors (r.0.6; i.e. the predictor that performed worst in the univariate model) and normal- ized the remaining covariates. A stepwise approach was taken to reduce the total number of competing covariates to be included in each final occupancy model for fosa, cat and dog. Firstly, the detection probability was modelled, with the most significant combination of detection covari- ates (Site and Effort) selected. Secondly, potential occupancy covariates were modelled independently with selected detec- tion covariates, with the best-performing uncorrelated co- variates retained (Table 1).We used the Akaike information criterion (AIC) and model selection to rank competing models, and reported those with AIC,2.0. Covariates that attained a summed model weight .0.50 were consid- ered to be important predictors of occupancy (Barbieri & Berger, 2004).


FIG. 2 Estimated site occupancy for the fosa Cryptoprocta ferox, cat Felis sp. and dog Canis lupus familiaris in Ankarafantsika National Park (ANP) and Andranomena Special Reserve (ASR) in Madagascar (Fig. 1). The boxes represent median site occupancy with upper and lower quartiles (25% greater and 25% lesser than the median); whiskers represent maximum/minimum values, black dots naïve occupancy, and white dots outliers.


We ran a goodness-of-fit test to examine the model’s


likelihood of being correct (P.0.05) and determine how well it fitted the data (measuring overdispersion as ĉ). Species occupancy was predicted across both sites, account- ing for the important covariate predictors.


Results


Landscape features and site detections With a sampling effort of 8,730 nights across both sites, we recorded the presence of three native and three exotic carni- vores (Table 1). The survey in Andranomena Special Reserve was shortened as a result of camera-trap theft (35 days vs 80 days in Ankarafantsika National Park). Overall, the land- scape of the Park was more degraded (GFC 75.32%) than that of the Reserve (GFC 97.16%). The mean distance from camera stations to the nearest village and to the forest edge was considerably less in the Park than in the Reserve (Table 1). In total, 311 independent detections of fosaswere recorded


(226 in the Park, 85 in the Reserve). In the Park, E. major was detected once, and in the Reserve M. decemlineata was de- tected twice. Small Indian civets were absent from the Reserve; in the Park they were detected almost exclusively in savannah and degraded land. These low detection rates prohibited occupancy modelling for these three species. Trap success was higher for dogs, zebu and humans in the Park, and for cats and birds in the Reserve (Table 1).


Oryx, 2020, 54(6), 828–836 © 2019 Fauna & Flora International doi:10.1017/S003060531800100X


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