Distance sampling with camera traps 673


FIG. 3 Detection probability and probability density for the models selected for estimating density. The bars show the data distribution, and the line represents the model fit. The heights of the bars are scaled so that they cover the same total area as the area under the line, to show how well the detection function fits the data.


densities in our study are low compared to those of Spiti can be expected because of differences in habitat type and topog- raphy. The Spiti landscape comprises vast trans-Himalayan meadows (Biotic Province 1B; Rodgers et al., 2000), whereas our study area consists primarily of narrowvalleys and gorges with rough terrain and barren slopes (Biotic Province 1C; Kumar et al., 2017; Plate 1). The differences of bharal density estimates and mean group sizes (9.6 in Nilang valley vs 13.1 in Kibber, Spiti) between these two areasmay thus be a result of differences in habitat quality. In addition, Nilang valley is affected by anthropogenic disturbances such as hunting (Bhardwaj et al., 2010), livestock grazing (Chandola, 2009; RP pers. obs., 2017) and presence of free-ranging dogs (Pal et al., 2020). The differences could also be caused by different survey techniques.Wewere unable to estimate bharal density using the point count distancemethod because of insufficient observations. The double observer method used to estimate bharal density in trans-Himalayan habitat requires visual


coverage of the entire survey area in a short period, a require- ment that could not be fulfilled in our study because parts of the study area were inaccessible and visual coverage was insufficient (Plate 1). The density of Himalayan musk deer was higher in sum-


mer (0.4 ± SE 0.1 individuals/km2)than winter (0.1 ± SE 0.05 individuals/km2). The analysis of seasonal habitat use in the study area also showed a trend of decline in captures at high elevations (Pal et al., 2020) in winter, possibly because musk deer migrate to lower altitudes during periods of heavy snowfall. Similar seasonal movements were also observed in other areas (Anwar & Minhas, 2008; Dendup & Lham, 2018). Other studies using the silent drive count meth- od in Kedarnath Wildlife Sanctuary estimated musk deer density to be 3.7 ± SE 0.2 individuals/km2 in 1989–1991 (Sathyakumar, 1994), 2.2 individuals/km2 in 1994–1995 (Sathyakumar & Malik, 2006)and 1.2 individuals/km2 in 2000 (S.Sathyakumar,unpubl. data). Thesestudies mayhave


Oryx, 2021, 55(5), 668–676 © The Author(s), 2021. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S003060532000071X


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