Mongolian gazelle population assessment 765


during the second count that had been observed in the first count. When summing up, taking into account the newly identified groups, the total number in the repeated count zone was 1,197 individuals (i.e. 15% more than the minimum survey value). Thus, based on the results from the double counting method, the number of gazelles that we counted in- creased by 15%to account for the groups that we missed. The inaccuracy associated with group size estimation was ,5%. Gazelle density was 3.30 gazelles/km2, producing an estimate of 21,701 gazelles (95%CI = 20,616–22,785 individuals) across a 6,572 km2 area.We counted 4,214 (n = 61 groups) and 485 (n = 28 groups) individuals during the transect surveys in the west Krasnokamensk and north Onon River areas, with re- sulting density estimates of 5.50 and 0.37 gazelles/km2,re- spectively. Experts estimated that c. 3,300 gazelles occupy Sokhondinsky Nature Reserve and 350 gazelles the north Daursky area. These findings suggest that there are a total of 30,050 gazelles across a 10,089 km2 region in Russia (Supplementary Table 1).


Discussion


We combined results from various surveys conducted in Mongolia and Russia, covering almost the entire global range of the Mongolian gazelle, with the exception of 5% of its range in China. This represents the first attempt to produce a near-range-wide estimate of the gazelle popula- tion. Our estimated total population size is c. 2.14 million in- dividuals (Supplementary Table 1), which is probably an underestimate. These results confirm that the gazelle is one of the most numerous open-plains ungulates globally. Other abundant species that are comparable with respect to their ecology and life history are wildebeest Connochaetes taurinus and Connochaetes gnou on the Serengeti plain of Africa (c. 1,560,000 individuals; Estes & East 2009), saiga antelope Saiga tatarica in Central Asia (c. 1,318,800 individuals; ACBK, 2022) and pronghorn ante- lope Antilocapra americana in North America (c. 1,000,000 individuals; IUCN, 2016a). However, some of these esti- mates are not recent and require updating. Amongst the range states, Mongolia holds the largest


proportion (99%) of the global gazelle population and is thus the main stronghold for the species. Our estimates from Mongolia represent a 52% increase since the last at- tempt to estimate the population in 2005 (Olson et al., 2011). Comparisons of results from regions covered by both surveys indicate that density estimates from the 2005 (c. 1.12 million individuals) and 2020 (c. 1.99 million indi- viduals) surveys were similar (5.14 gazelles/km2 in 2005 and 4.72 gazelles/km2 in 2020). This suggests that the popu- lation has at least remained stable across this important part of the species’ range. In Mongolia, gazelle densities are generally increasing from themore arid west towards the east, which experiences


more precipitation. Density estimates west of the Trans Mongolian Railway, for instance, are the lowest (0.97 gazelles/km2; 2.3–11.6 times less than regions east of the rail- way). Since the late 1950s, the Trans Mongolian Railway has become a nearly impenetrable barrier to the longitudinal movement of gazelle herds and a well-documented source of mortality (Ito et al., 2008, 2013a). It is likely that gazelle numbers west of the Trans Mongolian Railway are lower be- cause this region is more extensively occupied by livestock and because the railway corridor fencing restricts gazelle mobility across this portion of the range (Ito et al., 2013a; Batsaikhan et al., 2014). The c. 30,000 gazelles estimated to permanently occupy


Russia are the result of a successful reintroduction that began in the 2000s, following the extirpation of the species from Russia in the 1970s (Kirilyuk, 2007). In recent decades the transboundary areas have become refuges for the gazelle, particularly for the herds emigrating from Mongolia during resource-poor months (e.g. summer droughts and harsh winters; Olson et al., 2009b; Kirilyuk, 2021). Since 2019, gazelle numbers in Russia sometimes exceed 100,000 individuals during winter when gazelles migrate north from Mongolia in search of better pasture and to escape deep snow (Kirilyuk, 2021). Access to the edges of the spe- cies’ range is critical as these regions are more resilient to stochastic weather events and the impacts of the poorly understood effects of climate change on habitat quality. Recent estimates from China are not available in the lit-


erature and experts from the country did not respond to our queries. In Hulunbuir prefecture, 522 individuals in 66 groups were observed during the winter of 2005–2006 (Luo et al., 2014). Historically gazelles were widespread across northern China, with as many as 500,000 individuals there prior to the 1950s (Gao et al., 1996). However, the population in that region was believed to be less than 8,000 individuals in 2000 and mostly to occur along the border region with Mongolia (c. 75,000 km2 or 25% of the historical range) in eastern Inner Mongolia, Western Hulunbuir and around Dalai Lake (Wang et al., 1997; Jin &Ma, 2004). Because of a declining population and insuf- ficient information regarding the current status of the spe- cies, it is crucial that China promptly implements measures that prioritize monitoring and conservation of the gazelle. Notably, the Chinese government has made significant ef- forts to conserve the Tibetan antelope Pantholops hodgsonii by effectively safeguarding the movement corridors of this species (Shi et al., 2018). Similar efforts should be extended towards researching and conserving the Mongolian gazelle within China. The gazelle population remains large and widely distrib-


uted and continues to provide important ecosystem services such as redistribution of nutrients through the movements of the gazelles across the landscape, maintenance of forage diversity, and provision of prey for predators and carrion for


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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