760 B. Buuveibaatar et al. Accurate and precise population size estimates are neces-
sary to prioritize management and conservation actions for the gazelle. They often occur in large groups, with up to 250,000 individuals (Olson et al., 2009a). This, together with their distribution over vast geographical areas and long-distance nomadic movements creates logistical and analytical challenges for deploying robust monitoring pro- grammes. Aerial surveys involving well-defined statistical methods and analyses are ideal to overcome these difficul- ties (Singh & Milner-Gulland, 2011). However, lack of suit- able aircraft, capacity and funds make this methodology infeasible for regular monitoring. Surveys using ground- based distance sampling offer an established, cost-effective al- ternative for monitoring gazelle populations (Olson et al., 2005). The most recent reliable estimates of 1.13 million ga- zelles (95%CI = 843,410–1,504,500)inhabiting 220,000 km2 of grassland habitat to the east of the Trans Mongolian Railway in Mongolia were obtained from distance sampling line transect surveys conducted in 2005 (Olson et al., 2011). Herewe present the first near-range-wide estimate of the
gazelle population obtained from ground-based surveys across Mongolia and Russia. In addition, we provide anec- dotal accounts of the gazelle’s status in China. The surveys in Mongolia used distance sampling line transect methods (Olson et al., 2011; Buuveibaatar et al., 2017), except for the isolated population in western Mongolia, for which total count methods were deployed. The population size in Russia was estimated using a range of methods that have been implemented previously by local rangers: simultan- eous counts, line transects and accounts of recent observa- tions by local experts. Density and abundance estimates derived from data collected across the species’ entire range are useful for assessing the effectiveness of conservation efforts, prioritizing threats and supporting the development of future management goals.
Study area
The estimated global range of the gazelle is 746,281 km2,of which 91%(681,863km2) is inMongolia, 5%in China (34,718 km2) and 4% in Russia (29,700 km2; Fig. 1). Fencing along the 1,359 km national border between Mongolia and China impedes gazelle movement and effectively separates these populations. In contrast, transboundary movements can occur across the 524 km border between Mongolia and Russia as fences are either absent or were laid down dur- ing periods when large numbers of gazelles were observed in the border area. The gazelle range within Mongolia is mostly continuous; however, the population in and around Khomiin Tal National Park in western Mongolia is isolated (c. 600 km from the main range; Fig. 1). In Russia, gazelles are known to occur in five distinct areas during the summer, which are divided by natural (rivers and mountains) and anthropogenic (railways) barriers. The climate across the region is continental, with an ex-
treme temperature range of −45 to +42 °C. Precipitation decreases from the north-east to the south-west, mainly
falling during a few months in summer (June–August). There are ponds, lakes and rivers scattered throughout the region, especially in the Daurian Steppe that stretches across north-eastern Mongolia and the southern Siberian region of Russia. Availability of resources such as vege- tation cover and surface water is highly dynamic, driven by spatio-temporal variation in precipitation patterns (Vandandorj et al., 2015; Payne et al., 2020). There is an elevational gradient from 600 minthe east to 2,500 min the west. In Mongolia, the gazelle range falls within 13 aimags
(provinces or states) and 128 soums (regional districts), where c. 32 million livestock were held in 2020 (46% sheep, 42% goats, 6% horses, 5% cattle and 1% camels; National Statistics Office, 2020). The Trans Mongolian
FIG. 1 Mongolian gazelle range and the population survey regions (central and eastern Mongolia, southern Gobi and Khomiin Tal National Park) during 2019–2020 in Mongolia. The 2020 gazelle population survey region in Russia comprises five zones (areas) including (I) Daursky Protected Area, (II) Dzeren Valley Protected Area, (III) west Krasnokamensk, (IV) north Onon River and (V) Sokhondinsky Nature Reserve and north Daursky.
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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