Northern white-cheeked gibbons in Lao 769
FIG. 1 Map of Nam Et-Phou Louey National Protected Area in Lao, showing gibbon survey sites on four management sectors (patrol sectors) and regional ranges of the northern white-cheeked gibbon Nomascus leucogenys.
Gibbons may not perform duets every day and their call-
ing can be affected by factors such as weather conditions and season (Cheyne et al., 2008; Coudrat et al., 2015). We there- fore recorded weather conditions (i.e. presence of direct sunlight, wind, cloud or fog) at the beginning of each survey to assess their possible influence on gibbon detection prob- ability. Weather conditions were recorded as binary values (e.g. any presence of direct sunlight was coded as 1 and complete absence as 0). We recorded five landscape and human disturbance
variables as potential predictors of gibbon group abundance: area of mixed deciduous forest (%), altitude (m) measured at the centre of the sampled area, standard deviation of slope (ruggedness; Riley et al., 1999; Dawrueng et al., 2017), dis- tance (m) from the centre of the sampled area to the bound- ary of the totally protected zone, and a hunting pressure index (Table 1). We selected these variables because gibbon distribution is associated with forest type (Geissmann et al., 2000), altitude and terrain ruggedness (Kim et al., 2011), dis- tance to forest edge or road (Phoonjampa et al., 2011; Akers
et al., 2013), and level of human disturbance (Phoonjampa et al., 2011). We obtained all variables from the databases of the Protected Area headquarters and the records of the WildlifeConservation Society Lao Programme.We calculated
TABLE 1 Description of the site covariates collected and calculated within a 1-km radius around each survey site.
Covariate code
deciduous elevation
slope
distance hunting
Description
Area of mixed deciduous forest (km)
Mean elevation (m)
Standard deviation of slope (ruggedness) (°)
Distance to the boundary of Totally Protected Zone (km)
Hunting pressure index (hunting signs per patrol effort)
Oryx, 2020, 54(6), 767–775 © 2019 Fauna & Flora International doi:10.1017/S0030605318001515 Mean (range) 2.23 (0.16–3.14)
1,369 (1,095–1,978) 9.02 (6.95–11.51)
4.68 (0.00–10.44) 0.04 (0.00–0.24)
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
