Winters in the Gobi desert–which covers parts of northern and northwestern China and southern Mongolia–are usually long and very cold, but the winter of 2009/2010 was particularly severe, a condition Mongolians refer to as "dzud". Millions of livestock died in Mongolia and the reintroduced wild Przewalski’s horse population crashed dramatically.

Dr. Petra Kaczensky and Dr. Chris Walzer from the Research Institute of Wildlife Ecology of the University of Veterinary Medicine, Vienna, have used spatially explicit loss statistics, ranger survey data, and GPS telemetry to provide insights into the effect of a catastrophic climate event on wild horses, wild asses, and livestock that share the same habitat but show different patterns of spatial use.

In Mongolia, extreme weather conditions–droughts followed by cold and snowy winters–occur at irregular intervals. However, the dzud of 2009/10 was the most extreme winter Mongolia had experienced in the past 50 years. Fifteen out of Mongolia’s twenty-one provinces were declared disaster zones and over 7.8 million livestock, 17% of the national stock, are believed to have perished.

Przewalski’s horses have been reintroduced intto Mongolia since 1992 and there are now free-ranging populations in Hustai National Park in central Mongolia and in the Great Gobi B Strictly Protected Area (SPA) in southwest Mongolia. Due to its special location at the fringe of the Dzungarian basin, flanked by high mountains, the Great Gobi B SPA received particularly high amounts of snowfall in the winter of 2009/10. Most snow came with weather from the west and when the snow clouds hit the Altai Mountains on the eastern edge of the Great Gobi B SPA they discharged large amounts of snow, resulting in a strong east-west gradient in snow depth. The high, tightly packed snow made it hard for animals to gain access to the vegetation under the snow