764 B. Buuveibaatar et al.


estimates was attributable to group size (53%), whereas en- counter rate and detection probability contributed 31%and 16% of the variance, respectively. In contrast, uncertainty in the abundance estimates for the 2020 survey was mostly because of encounter rate (54% of the variance), followed by group size (41%) and detection probability (5%). During the census in Khomiin Tal National Park, the


rangers observed 1,134 individual gazelles in 37 groups (mean = 30.7 ± SD 40.9 gazelles). Density was 0.27 ga- zelles/km2 for this small and isolated population across the 4,114 km2 study area (Supplementary Table 1). The density estimate for the southern Gobi was 0.52


gazelles/km2, and for the west stratum 0.97 gazelles/km2, giving a mean density of 0.75 gazelles/km2. The study area of south-western Mongolia was estimated to be 146,288 km2. Based on these figures, the estimated gazelle popula- tion size in the south-western Mongolia region was c. 109,716 gazelles (Supplementary Table 1).


Population surveys in Russia


FIG. 3 Detection probability functions for Mongolian gazelle groups in (a) the southern Gobi in 2019 and (b) the eastern Mongolian Steppe in 2020. The curved line represents the best- fit model describing how the detection probability changes with distance.


During the survey in the Daursky and Dzeren Valley pro- tected areas, we observed 18,898 individuals in 475 groups. During the repeated counts, we recorded 1,020 animals in 27 groups at the first count and 1,097 animals in 29 groups at the second count. During the first of the repeated counts, the teammissed two gazelle groups that were seen during the second count; similarly, the team missed a single group


TABLE 2 Mongolian gazelle encounter rate (groups/km), mean group size and expected group size, all with 95% CIs, for the southern Gobi in 2019 and central and eastern Mongolia in 2020.


Stratum Southern Gobi


Central & eastern Mongolia West


Central


North Kherlen South-west Menen


Year Encounter rate (95% CI) Mean group size (95% CI) Expected group size (95% CI) 2019 0.01 (0.007–0.02)


2020 0.50 (0.35–0.72) 2020 0.11 (0.74–0.16) 2020 0.55 (0.36–0.83) 2020 0.60 (0.49–0.73) 2020 0.18 (0.81–0.41)


Overall (central & eastern Mongolia) 2020 0.71 (0.58–0.86)


16.4 (8.1–33.0) 22.2 (17.6–28.0)


97.0 (70.7–133.2) 241.0 (163.8–354.6) 42.3 (30.7–58.3) 82.7 (41.7–164.3) 91.3 (73.5–113.3)


11.5 (6.1–16.9) 15.7 (12.6–19.5)


75.8 (56.3–102.0) 117.1 (71.5–191.8) 30.8 (22.8–41.8) 41.4 (24.3–70.4) 48.6 (41.3–57.3)


TABLE 3 Estimates of gazelle group density (groups/km2), individual density (individuals/km2) and abundance, with 95% CIs, and overall percentage coefficient of variation (%CV) for the southern Gobi in 2019 and central and eastern Mongolia in 2020.


Stratum Southern Gobi


Central & eastern Mongolia West


Central


North Kherlen South-west Menen


Overall (central & eastern Mongolia) Year


Group density (95% CI)


2019 0.03 (0.02–0.06) 2020 0.06 (0.04–0.08)


2020 0.13 (0.09–0.20) 2020 0.06 (0.04–0.10) 2020 0.07 (0.05–0.09) 2020 0.22 (0.09–0.50) 2020 0.08 (0.07–0.11)


Individual density (95% CI)


0.52 (0.21–1.30) 0.97 (0.63–1.47)


10.30 (6.31–16.81) 7.86 (4.19–14.76) 2.26 (1.57–3.25) 9.21 (3.94–21.53) 4.72 (3.47–6.41)


Abundance (95% CI)


40,899 (16,307–102,580) 132,010 (86,940–200,440)


765,350 (469,040–1,248,800) 636,890 (339,460–1,194,900) 240,970 (167,260–347,160) 216,060 (92,415–505,130)


%CV 49.04


20.98 24.27 32.56 18.65 41.04


1,991,300 (1,464,900–2,706,700) 15.63 Oryx, 2024, 58(6), 759–768 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323001515


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