832 S. D. Merson et al.


TABLE 2 Species covariate occupancy models for fosa, cat and dog, with Akaike information criterion corrected for a small sample size (AICc), relative change in Akaike information criterion from top model (ΔAICc), Akaike weight (AICc weight), number of parameters (K), and −2 log likelihood.


Species Fosa


Occupancy model1


Cat + Dog + GFC20 + TCA Cat + Dog + GFC20 Cat + GFC20


Cat + Dog + TCA AICc


1,195.32 1,195.54 1,195.81 1,195.85


Cat + Dog + GFC20 + TCA+ TW 1,196.20 Cat + Dog + Road + TCA Cat + Dog + GFC20 + TW Cat + Dog + GFC20 + Lemur


1,196.30 1,196.41 1,196.44


Cat Dog


Cat + Dog + GFC20 + Lemur + TCA 1,196.49 Bird + TW+ VCF Bird + TW


Civet + Forest + NP + TW Forest + Lemur +NP +TW Civet + TW+ VCF


FD + Forest + Lemur +NP +TW Civet + FD+ Forest + NP + TW Forest + NP + TW+ Zebu


1,558.00 1,558.33 1,288.57 1,288.68 1,289.17 1,289.46 1,289.51 1,289.56


ΔAICc 0.00


0.22 0.49 0.53 0.89 0.99 1.09 1.12 1.17 0.00 0.33 0.00 0.11 0.60 0.89 0.94 0.99


AICc weight K 0.08


0.07 0.06 0.06 0.05 0.05 0.04 0.04 0.04 0.23 0.20 0.10 0.09 0.07 0.06 0.06 0.06


8 7 6 7 9 8 8 8 9 7 6 9 9 7


10 10 9


−590.34 −591.59 −590.50 −588.41 −589.60 −589.65 −589.67 −588.55 −771.59 −772.86 −634.55 −634.61 −637.14 −633.83 −633.85 −635.05


−2 log likelihood −589.11


1Cat, Dog, Lemur, Bird, Civet and Zebu, species encounter rates (total detections/total sampling days × 100); GFC20,% global forest cover at 20% threshold level (30mresolution); TCA, total core area in each patch (m2);TW, trail width (m); VCF, vegetation continuous field (% forest cover at 250mresolution); Forest, forest classification (old-growth, degraded, savannah); NP, total patches of a class type; FD, distance to forest edge (m).


Covariate and model validation


Our two survey covariates (Site and Effort) were contained in the best performing detection model (SupplementaryTable 1). Consequently, they were included in all subsequent model- ling of occupancy with occupancy covariates. Our correlation matrix revealed significant correlations between competing covariates (Supplementary Table 2). Six covariates (Number of patches, Landscape patch index, VCF, Elevation, Mean distances to village and forest) were discarded prior to constructing the multivariate fosa occupancy model. The goodness-of-fit test indicated significant overdispersion, and consequently five sites were removed (42 detections in total).


Occupancy


There were no statistically significant differences in occu- pancy between the two study sites (P,0.05). The mean fosa occupancy across both regions was 0.724, being marginally higher in the Reserve (0.757) than in the Park (0.692; χ2 = 0.003,df = 1,P = 0.959; Fig. 2). Mean cat occu- pancy was 0.736, and was marginally higher in the Reserve (χ2 = 2.844,df = 1,P = 0.092). Mean dog occupancy was 0.999, and was considerably higher in the Park (χ2 = 2.306, df = 1,P = 0.129). Cat and dog trap success, GFC20 and total core area


were the most important covariates (summedmodel weight .0.5; Supplementary Table 3) in explaining fosa occupancy across the landscape (Table 2). Dog trap success had a weak positive relationship with fosa occupancy, whereas cat trap


success, GFC20 and total core area had a negative relation- ship with fosa occupancy (Table 3). Catoccupancywas best explainedby birdtrapsuccess, trail


width andVCF(Table 2). Bird trap success andtrailwidthwere negatively correlated with cat occupancy, whereas there was a positive association between occupancy and VCF (Table 3). Dog occupancy was best explained by civet trap success,


forest type, number of patches and trail width (Table 2). Civet trap success and trail width were positively correlated with dog occupancy, whereas old-growth, savannah and total patches negatively affected occupancy (Table 3).


Discussion


Overall our results were unclear regarding the relationship between the fosa, landscape degradation and exotic species, with no clear relationship evident between fosas and de- gradation, but a clear negative relationship between fosas and cats. Our findings regarding dog and cat occupancy concur with previous studies documenting the negative effect of exotic species on Madagascar’s endemic carnivores (Gerber et al., 2012a; Farris et al., 2015b, 2016; Murphy et al., 2017). The fosa appears to be more resilient to habitat disturbance within contiguous forests than other euplerids but the loss of Madagascar’s forest is likely to inhibit their long-term persistence. The high occupancy of free-ranging cats and dogs in the landscape indicates considerable com- petition with fosas through the consumption of shared prey (Brockman et al., 2008) and exclusion from habitat. The


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


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164