Large mammals re-introduced into harsh and unpredictable environments are vulnerable to stochastic effects, particularly in times of global climate change. The Mongolian Gobi is home to several rare large ungulates such as re-introduced Przewalski's horses (Equus ferus przewalskii) and Asiatic wild asses (Equus hemionus), but also to a millennium-old semi-nomadic livestock herding culture.The Gobi is prone to large inter-annual environmental fluctuations, but the winter 2009/2010 was particularly severe. Millions of livestock died and the Przewalski's horse population in the Gobi crashed. We used spatially explicit livestock loss statistics, ranger survey data and GPS telemetry to provide insight into the effect of a catastrophic climate event on the two sympatric wild equid species and the livestock population in light of their different space use strategies.Herders in and around the Great Gobi B Strictly Protected Area lost on average 67% of their livestock. Snow depth varied locally, resulting in livestock losses following an east-west gradient. Herders had few possibilities for evasion, as competition for available winter camps was high. Przewalski's horses used three different winter ranges, two in the east and one in the west. Losses averaged 60%, but differed hugely between east and west. Space use of Przewalski's horses was extremely conservative, as groups did not attempt to venture beyond their known home ranges. Asiatic wild asses seemed to have suffered few losses by shifting their range westwards.The catastrophic winter 2009/2010 provided a textbook example for how vulnerable small and spatially confined populations are in an environment prone to environmental fluctuations and catastrophes. This highlights the need for disaster planning by local herders, multiple re-introduction sites with spatially dispersed populations for re-introduced Przewalski's horses, and a landscape-level approach beyond protected area boundaries to allow for migratory or nomadic movements in Asiatic wild asses.

No abstract

Central Asian remote rangelands are home to several charismatic, rare and far ranging ungulates which are increasingly becoming under pressure from human encroachment. Population monitoring is challenging due to the vast expanse of the species ranges, tight budgets and limited availability of suitable fixed winged-aircraft. Consequently, many current population estimates are based on pragmatically designed ground-bound transect surveys. Although, ample literature exists on how to design surveys in an ideal world, little effort has been made to demonstrate the potential and limitations of a time-series of ground-bound transect surveys under real world constrains.Since 2003 we have been monitoring the two sympatric steppe ungulates, Asiatic wild ass ("khulan", Equus hemionus) and goitered gazelles ("gazelle", Gazella gutturosa), in the Great Gobi B Strictly Protected Area in south-western Mongolia using ground-bound line transects. Both species showed clear species-specific seasonal variation in group sizes which seem related to birthing and mating periods. Data on annual recruitment were impeded by the long flight distances and the difficulty to reliably identify and count young of the year. Distribution of khulans and gazelles showed clear speciesspecific seasonal patterns and highlighted the importance of two oasis complexes. Population estimates of 33 surveys covering 10,383 km² were highly variable even between consecutive surveys and had huge 95% confidence intervals (khulan: range: 1,707 to 45,040, gazelles: range: 2,564 to 10,766) making them unsuitable to obtain robust baseline population estimates.Although our individual surveys were poor measures of population abundance, they provided important data on group sizes and species distribution and are presently used for Bayesian hierarchical trend modelling and species specific habitat suitability analysis. The ground surveys are relatively inexpensive as compared to aerial surveys and thus can be conducted at short temporal intervals, engaging park staff and researchers with local people thereby helping mutual understanding, information transfer, and detection of illegal activities.